Originally authored by Mr. Len Hensel, BSME, MS-PDD Wheel Engineer
The five-piece rim design has been the standard for construction and mining wheels for well over 60 years. In general, the functional design has remained the same with adaptations for changes the tire construction (radial tires) and new tire sizes. The tire capacities have grown over this time as well. The adaptations have allowed the rims to maintain their durability expectations.
However, extreme applications such as steel slab haulers have push the durability envelope beyond what the rims can sustain for long term life. In extreme service conditions, five piece rim/wheel designs, can exhibit fast wearing of mating surfaces and rim cracking due to the higher loads and application speeds. Characteristics of radial tire constructions have added to field issues of the rims. Wheel engineers evaluated the failure modes with slap hauler rims and observed the following characteristics:
Wheel engineers looked at the observed issues and implemented several incremental design changes to address the problem. Some of these changes have been:
The results of the modifications were:
While the service life was improved, it was not sufficient to achieve a service life that was acceptable to end users. Since the traditional changes did not yield a sufficient improvement, a new solution was needed. It was decided that an integrated design which tied the side flange to the back section would be tested in this machine application.
One-piece fixed flange designs are not new to off-road applications. They have been used in rim and wheel designs for over 100 years in smaller diameter applications. Typical applications have been tube type track rims, motor graders and small front-end loaders. In the last 15 years, one piece back sections have been used in wheel designs on medium size loaders and some special application 33” machines.
A fixed flange design will:
A series of FEA (Finite Element Analysis) simulation models were run to verify that the fixed flange design would have sufficient strength to carry the loads of extreme service applications. Three load conditions were also used to evaluate the fixed flange design.
Load Case 1 – 66,000 lbs. (30,000 Kg) @ 110 psi. (7.6 bar)
Load Case 2 – 132,000 lbs. (59,900Kg) @ 110 psi. (7.6 bar) (Impact load)
Load Case 3 – 110,000 lbs. (49,900 Kg) @135 psi (9.3 bar) (Extreme Service Loading)
The conclusion of the FEA simulation models was that the new fixed flange design is very robust and will adequately carry the extreme service loads imposed by radial tires.
The predicted deflections of the FEA simulations were evaluated to determine the effects of the fixed flange back design compared to the baseline model which was the typical 5 piece design. The results show that the deflections of the new fixed flange back is 30% lower than the baseline model at the standard load condition. The reduced deflection of the fixed flange back demonstrates the improved stiffness of the section. This will have a positive impact on the tire and lower tire bead area.
The conclusion of the computer modeling was that the new “fixed flange design” rim design is very robust and will handle the loads and stresses imposed by radial tires. The deflections of the computer models were evaluated to determine the effects of the one-piece design.
The new fixed flange design has placed into a controlled field trial at a steel mill to verify the results in a real world environment. The fixed flange was specified to be made from a seamless rolled ring to eliminate are issues from a seam weld. A HSLA (High Strength Low Alloy) grade material with exceptional characteristics was specified to ensure that the component would have exceptional fatigue life. The component was fully machined to the final profile to create the best possible fit with the tire. Rim knurling was also specified to further contribute to reducing tire indexing. Full penetration circumferential weld joints were specified to facility inspection and verification that the welds were free from internal defects
Slab hauler applications are typically severely loaded (100,000 Lbs./45,360 Kg per tire) as compared to the typical haulage truck. This application was specifically selected as a field test because of the high load nature of the equipment and the high air pressures that are used (typically 135 PSI / 930 kPa). The cracking mode of the five piece assemblies is comparable to the mode seen in typical haulage applications at quarries and small mining operations.
Because of the high load environment, the cracking modes in the slab hauler application occur much earlier in the life of the part than would be expected in an average haulage application. The typical life of the rim in the slab hauler application, depending on which five-piece design is used, “varies from 800 hours up to about 3,000 hours”. After this, replacement of rim base components is required. A high cost for the end user. It is important to note that the slab hauler application is operating “well outside the norm” for a 27.00 R 49 tire application. These loads encountered would not be approved for the standard high-speed (30 Mph/50 KPH) applications.
The true test of any design is how it will perform in the real world, in a real operation where the environment has all the application variables that are not fully represented in the computer simulations. Several sets of wheels were placed in service on slab haulers. The rims were inspected are 3,000 hours & 5,000 hours of operation.
The results were phenomenal. At 3,000 hours the parts still had a like new look to them. While the flange area shows that the paint has been removed because of movement of the lower bead area of the tire. The bead seat surface of the rim shows very little wear which suggests that the tire bead has a more stable surface (less deflection)
A NDT (Non-Destructive Testing) examination of the rear radius of the fixed flange did not show any evidence of early fatigue crack initiation. At 5,000 hours, the fixed flange design parts did not have any indications of fatigue cracks.
This picture shows the condition of a fixed flange design after 5,000 hours of operation.
An unexpected benefit that was derived from the new fixed flange design was a significant improvement in tire indexing and lower bead area durability. This improvement was observed by the end user. This can be translated into to better equipment up time and a reduction of their tire costs.
The new 49” four-piece design has achieved its intended design objectives and more:
1. Fretting has been eliminated on the back flange area of the rim.
2. There has been minimal impact to the weight added to the total rim assembly weight (100 lbs. /45kg).
3. Improved stability of the tire bead area.
4. Virtually no tire slippage.
5. Minimal metal erosion under the bead of the tire.
6. Extended life to the rim and reduced down time because of broken rim components
7. Ability to handle the new 80 series radial tires.
8. Improved tire life in the slab hauler application. (Normal casing life on five piece designs was 2,500 to 3,500 hours. With the four-piece rim casing life has been extended to 4,500 hours to 5,000 hours.)
All of the above benefits have resulted in reduced maintenance cost and increased tire utilization. The net result is reduced equipment operational cost, which in turn contributes to improved profitability for the steel mill.
The original design improvements and testing were done in 2000 and 2001. Since that time, many rims have been put in service on slab haulers in Canada and the U.S. All the rims have been subject to periodic NDT inspection processes at factory authorized inspection and repair facilities. Critical areas are inspected and necessary repairs done to repair or replace defective rim parts such as gutter sections, center sections and rim locators.
The scheduled inspections and repairs on an as needed basis have extended these rims service life well beyond anyone’s expectations for the rim design resulting is a very low cost of ownership and extended service life. A win-win deal for companies that own these rim products and the companies responsible for servicing them.
For more information about this product design and how it can work for you, contact Keith Heeres at the phone number at the top of this page.
Mr. Len Hensel, BSME, MS-PDD
Len has over 39 years of industry experience in providing wheel system solutions for the mining, construction and agricultural applications. He has worked extensively with the entire major off road equipment manufacturers and off road tire (OTR) companies to provide designs that meet the needs of new applications, pushing the envelope for greater load capacity and durability. He has worked in leadership positions in off the road wheel industry new product development, application engineering, new design validation, research and development projects, and quality assurance. He is a member of the Society of Automotive Engineers (SAE), participated in development of international standards (ISO) related to off the road wheels, and a past member of the Tire and Rim Association (TRA) representing the rim and wheel industry manufacturers.
Contact: [email protected]
This is a very long information packed article or post. I decided to cover it in one large post rather than several smaller ones. The Quick Navigation links above make it easier to navigate the relevant sections of the article you want to read. While I will mention some brands of products and provide links to those, they are for information purposes only. I am not endorsing any one product in this article.
The main goal for the owners, operators and mobile equipment managers is keeping their fleet of equipment working to maximum performance to meet production quotas. At the same time they want to minimize operational expenses and maximize their companies profit. Minimizing equipment maintenance costs is a top priority anywhere you work. Tire expenses are one of the top expense items for off the road equipment that roll on wheels and tires. Unscheduled equipment downtime due to tire failure is something these stakeholders want to minimize and is an issue they you can do something about. Downtime from flat or damaged tires can be extremely costly to fix as well as create additional problems such as backlogs in continuous service operations and service interruptions in mining and quarrying operations. Tires for them are a recurring expense as well and they have dramatic effect on total operating and daily productivity.
These stake holders in charge of rubber tired off road vehicles want to:
Commercial tire dealers are essential partners in accomplishing all these goals for them. Their machines don't perform well unless the tires and wheels on their machines are in optimal condition to do the job.
When the issue tire selection and flat proofing tires comes up there are several approaches to consider.
We're going to look at the issues like this:
If you are trying to solve the problem of how to make sure your off the road machine doesn't suffer from flat tires, how do you address the problem of tire flat proofing and solve it using the best solution at the least expensive cost?
First we need to ask ourselves some questions. For the moment, we will disregard tire tread considerations and just focus the issue of how to eliminate flat tires on off road vehicles. We need to understand and evaluate what your options are. You need to have a handle on all your machine and tires issues and consider how to address them most effectively. We need to evaluate how you would address the problem with a piece of equipment like a skid steer loader, a wheel loader, a forklift, a specialized piece of material handling equipment used in a factory environment or a piece of military equipment that must ready for fight or flight can be very different.
Let's consider each option one at a time.
There are many benefits of choosing to use pneumatic tires. Regardless of the tires design or application, all pneumatic tires are designed to:
The benefit of using pneumatic tires is they are made in a wide range of common tire sizes to fit standard wheels & rims, section widths, overall tires diameter, specialized rubber compounds, tire profile, tread designs, bias or radial construction and air pressure ratings. They usually offer the best choice for the combination of economy and comfort. They can run in many applications and are capable of performing equally well indoors and outdoors, and can be used in heavy and light duty applications. New tires are widely available from a variety of tire manufacturers, price and quality ranges. Tire and wheel packages can be easily be put together to fit nearly any machine.
The case against using pneumatic tires is simple. These tires must hold air to work. Tire air pressure is a key component of a mounted tire and wheel assembly. Maintaining that air pressure is key to the tire being able to perform as expected. Pneumatic tires are more easily damaged by nails, screws, rebar, and other hazards common on construction sites. Owners and users must check and maintain their tires’ air pressure consistently. The biggest cause of premature pneumatic tire failure is the failure to maintain optimal tire pressure.
So how do we make a pneumatic tire flat proof and still enjoy the benefits of a pneumatic tire?
Tireliner is a permanent, self-healing, urethane rubber sheet that is securely adhered directly to the inside of the tire casing of a pneumatic tire. Tireliner works by self-sealing over cuts, punctures and penetrating objects, and will prevent tires from going flat if punctured or cut by objects up to 1/4” in diameter. So objects like nails, screws, sticks, small metal objects and thorns will not leave a hole that will cause the tire to loose air pressure.
Tireliner offers sidewall protection as well as protection for the tread areas of the tire. The patented material actually allows the liner to immediately close over the zone of penetration and completely fuse, thus, air pressure loss is prevented.
Tire balance and structural integrity are not affected by the addition of the Tireliner material. Tireliner is excellent for applications where added weight may be undesirable or will create a problem. Tires lined with Tireliner are recappable and repairable. It is unaffected by temperature extremes in hot or cold climates, or tire air pressure.
Tireliner is a puncture sealing system that offers true sidewall protection as well as protection for tread areas. It provides a balanced, uniform thickness of self-healing rubber. It is also the only available system that conforms to any size geometry of tire and lasts the lifetime of the tire.
Tire balance and structural integrity are not affected by the addition of the tire liner. Tireliner was originally developed for the military and has been in commercial use for many years now.
Limitations of Tireliner
Tireliner can only be used in tires that are 24” or less in diameter. This size limitation is because the equipment available to apply the urethane material won’t accommodate large tire sizes.
Various companies around the world are capable of tyre lining. Nearly any tire in the size range their equipment can handle can be lined. Tyre liners work best when you purchase a new tire with the liner installed at the factory.
If you already have tires that you want to have lined, there are services where you can send the tires to get this done and have them sent back to you ready to mount back on wheels to be put back on machines.
Liquid tire sealants come in several formulations for both consumer and commercial tire uses. They have been on the market for several years. They are intended for quick and fast tire repairs when you don’t have time or you are not in a suitable area for changing tires.
There is some controversy about using many of the consumer grade tire sealers. Why?
First they are only a temporary fix. Intended to get you from where you stop to attend to your flat tire, to the nearest place you can get your tire fixed or replaced. They are not spare tires in a can and they are not a permanent fix. They have a very limited service life.
They are intended to fix small tire punctures of a ¼” or less in the tread face of the tire. Not in the sidewall of the tire.
Using these consumer grade sealers can invalidate your tire warranty. You need to investigate that before you use them.
They are not intended to be used in high performance tires at high speeds of travel.
Most commercial tire dealers hate them because of the mess they make and the difficulty of cleaning up the tires to patch them. Not to mention the mess they can make of the wheels and potential to damage TPMS systems.
Consumer grade sealers work fine for some applications but are not recommended for others. If used in car tires, some commercial tire dealers will add extra charges to a customer’s bill for the additional labor to clean up tires and wheels. While other dealers will decline entirely to work on tires that have been sealed with some of the commercial sealers.
Some of the consumer tire sealers are intended to work with ATV, consumer grass mowing equipment or smaller tires.
Some of the consumer tire sealants are manufacture specific and intended for OEM automotive use in vehicles and tires those manufacturers recommend.
Certain tire sealer kits are paired with small portable compressors and a sealant for repair of a flat. These are considered to be emergency tire inflation kits.
The aerosol can tire sealers can leave a sticky liquid mess in the tire that settles to the bottom of the tire when the vehicle is parked. Then as the vehicle reaches high speeds it will cause the tire to be unbalanced and create a lot of vibration. Depending on the brand the sealers can also be made of flammable materials. Read the labels and use them with care.
Commercial grade tire sealants are a different breed apart. The use of commercial grade sealants in tires is a preventative maintenance measure you can take to eliminate pneumatic tire flats from punctures to the tire up to ½” in size. These commercial grade sealants are designed and intended to be used continuously in the tires providing all the benefits they were designed for.
Liquid tire sealants are pumped into the tire through the valve stem. They coat the inside of the tire so they are ready to do their job instantly should an object puncture the tread creating a hole the needs to be sealed immediately. They will repair and prevent flat tires, seal minor cracks in inner wall of the tire, and continuously self-seal punctures. They can also stop valve leaks and leaks between the bead and rim.
There are several manufactures that make these commercial grade sealants. Some are made with Kevlar® or aramid fibers in the liquid formula. Others are using state of the art nano-technology to clot and fill the puncture hole. While not all tire sealants are the same as made by the manufacturers, the main benefits are:
DuPont™ Kevlar® The DuPont™ and all products denoted with ® or ™ are trademarks or registered trademarks of E. I. du Pont de Nemours and Company or its affiliates.
Like consumer grade tire sealants, there are differences in the commercial sealants as well. You will find lower grade products and premium products that have been tested and approved by OEM tire manufacturers, and independent tire and rubber testing labs. You also need to check and see if the commercial sealant you might be considering is safe for TPMS if you are using them. You also want to make sure the sealant you might be considering is non-flammable and how easily it is to wash out or clean up.
So far we have talked about how you can flat proof and make your pneumatic tires puncture resistant from the inside of the tire. What about protecting your pneumatic tires from the outside?
Couple ways to do that.
1. Use Tire Protection Chains to give your tires a coat of armor.
2. Use Tire Saver Shields ™ or other similar products to give your tires a side wall “shield”.
1. Protect tire treads and sidewalls from abrasions, cuts, gauges and punctures. These chains can extend the life of your expensive rubber tires from as many as 4 to 10 times (according to manufactures literature). They come in several interlinking ring systems, hardness ratings and ring or mesh designs. Because of the way they are designed, the chains are flexible and can adjust the tire as it moves over the operating surface while protecting the tires from sharp edged stones and abrasive surfaces.
In steel making and slag handling applications the Tire Protection Chains help to protect the tires from the intense heat of red hot steel slag. This slag material can reach temperatures approaching 2,200 degrees Fahrenheit. Wheel loaders have to handle and navigate around large and solid scrap pieces. The chains will protect the tires from punctures, burning tires and very abrasive ground conditions.
Tire Protection Chains can also be custom designed for specialized applications. All you need to do to fill out a form and contact the company with your requirements and an expert in chains will provide you with a personal consultation.
2. Tire chains give tires greater traction in icy, frozen, snowy or muddy conditions. When you’re having to deal with steep inclines, spinning wheels and season weather conditions, tire chains can be a critical safety item for heavy equipment.
Earthmoving tires are typically the most expensive cost of ownership item on wheel equipment and are very sensitive to cuts, punctures and other damage. Tire chains are indispensable when used on wheel loaders and underground mining equipment involved in hard rock mining and quarrying. Tire protection chains are also very beneficial in protecting machines involved in steel making, scrap handling and demolition work.
Unprotected tires can be worn out and deteriorate quickly when used in the above mentioned work environments. Tire protection chains offer and optimum level of protection to reduce tire maintenance costs.
Important note: Tire Protection Chains are not inexpensive. They are however reusable, repairable and they do an excellent job of protecting and extending the life of your rubber tires. And, they will add more weight to your wheel and tire assemblies. That added weight can be an advantage or disadvantage depending on your equipment owners perspective.
Main suppliers in the industry are:
Tire Saver Shields are the result of years of work creating tire sidewall protection for rubber tired military equipment. The goal of the product is to prevent and protect tires from “non repairable” sidewall damage that would occur from striking or moving against the sharp edges of rocks, metal objects or other objects that could be snagged by the tire sidewall. The construction of the product is also fire resistant as well. Remember its origin was military use.
Tire Saver Shield ™ is a registered Trade Mark of Hutchinson Industries.
Tire Saver Shields are available in several common tire sizes. Larger sizes for earthmover tires are being produced as well.
Tire Saver Shields are attached to wheels that mount the tires via a ring welded to the wheel flange. After the tire is mounted on the wheel and inflated the Tire Saver Shield is bolted to the attaching ring. The Tire Saver Shield conforms to the profile of the tire. It creates and heavy barrier between the tire sidewall and any potential damaging object the tire may encounter that could damage or puncture it.
How do you know Tire Saver Shields will work for you and your application?
If you are tracking your tires and documenting how and why you have lost tires, you just need to figure out how many tires you have lost due to “non-repairable” tire sidewall damage. Look for where you lost tires that still had useable tread, but the tire sidewall failed and you had to scrap a tire that would had still useful tread life. Those are the costly failures you want to eliminate. Tire Saver Shields have been proven to enhance the survivability of off the road tires in several applications. They are very effective in mining, quarrying, and heavy lift industrial forklift applications.
Tire Saver Shields are not inexpensive and require qualified installation. If you would like a consultation about how Tire Saver Shields can help you, give me a call.
Hutchinson is not the only company that makes a tire shield. The Rud company make a product they call the SideFlex.
Like the medieval knights of old, you can always outfit your expensive off the road tires with a new coat of armor and equip them with a shield to ward off the potential hazards of your work site that would destroy your tires.
These tires are almost completely flat proof, puncture resistant and cut resistant. There are specialized applications they are suitable for, size limitations, load and speed limitations and heat buildup issues.
Some of the most expensive, highly engineered and well constructed tires in the world are aircraft tires. Every aircraft tire is entirely handmade and very carefully constructed and inspected to the most stringent requirements of the FAA standards. There is no such thing as a bad aircraft tire which is why brand new they are very expensive. In fact they are overbuilt to withstand the unexpected conditions they may be exposed to. Blowouts on aircraft tires almost never happen. It they do, it us usually related to low inflation pressure of a tire or hitting a piece of debris on the runway.
General aviation tires almost always are built as bias-ply construction tires. Retreaded aircraft tires is an industry standard for commercial airliners and military aircraft. Aircraft tires are very different from consumer grade tires in this big way. Most aircraft tires on commercial airliners are pressurized to 200 PSI with nitrogen rather than air. Your typical car tire operates at between 30 to 40 PSI and are pressurized with air.
Aircraft tires are designed for:
Aircraft tires are made of very thick rubber, extra heavy sidewalls, heavy nylon ply cords and are formulated to resist all kinds of wear, abrasion, cutting, cracking and heat build up.
Since these tires are so heavily plied they are “almost” entirely puncture proof. This feature makes them very popular for a wide range of uses where the tires must be pneumatic. They are ideal for applications from agriculture, forestry, commercial mowing, mining, industrial uses, steel mills and scrap yards.
Aircraft tires are also easily recapable. The aircraft unique treads are buffed off and commonly used treads normally found on conventional tires can be molded right back on them. This can be done over and over again so long as the tire casing us undamaged and still useable. A multitude of tread designs and rubber compounds can be remolded to the aircraft tire casing.
Aircraft tires come in specialized sizes and require custom wheels to mount them. They could require industrial bolt together or 3-piece lock ring style wheels to mount them. If you don’t have these wheels already, complete mounted tire and wheel assemblies are available or can be custom built for your machine application.
These specialized tires are almost always tube type tires so they will require a tube and flap for your wheel. Those can be easily supplied with your assembly as well.
Size limitations are another consideration for aircraft tires. Certain sizes are difficult to get due to changes in the commercial and military aircraft markets. Some of the largest tires are made to fit military heavy bombers and there are only so many of those types of aircraft in service around the world.
By USAF Photo by Technical Sergeant Robert J. Horstman [Public domain], via Wikimedia Commons
Since these repurposed tires are built for high load carrying capacity at very high speeds (for example take-off and landing speeds of 150 to 200 mph), when you drop the operating speed of these tires you get extremely high load carrying capacities.
If you want to get added puncture resistance, you can always add one of the commercial grade liquid tire sealants to the aircraft tires and add all the benefits the products provide as well. Double up the protection. Some vendors of air craft tires do that when they supply the full tire and wheel assembly anyway.
The use of run-flats in consumer vehicles is and has been very controversial. Some high-end automobiles have offered vehicles with run-flat systems, but they are not widely used. They just never caught on and were very expensive compared to other methods of flat proofing and puncture resistance.
Run-flats and bead locks however in military vehicles are widely used and provide the benefits of making the wheel and tire assembly essentially bullet proof. The tire can be punctured with a bullet or projectile and the air will be lost, but the run-flat system takes over so the vehicle can continue to fight or drive away quickly. Run-flat systems for military equipment are proven to give the vehicle the ability to travel distances such as 20 miles to get the military crew out of the danger zone.
Beadlocks are also very popular for owners of off road machines (like ATV's, RV's, jeeps and trucks) and in off road racing.
Internal bead locks are different from run-flats in that they are bolted together or pressed into the inside the wheel to lock the tire beads in place when the tire loses air pressure. The vehicle can continue to roll (at a reduced speed) on the tire a small distance temporarily.
I mention run-flats and bead locks because they are a method of flat proofing pneumatic tires. For example, if you have a vehicle that has the ability to use wheel and tire sizes made for military type equipment and you can acquire surplus tire and wheel assemblies with the run-flats and bead locks, you can use these to flat proof your equipment. Naturally there are size limitations which these products are available in such as 20”, 21” and 24” diameter. And the wheels are specialized as well.
Examples where you may encounter these types of flat proofing methods applied to the tires and wheels are specialized trucks and emergency response vehicles like you might find are airports. However, most applications are military related.
Another feature of these wheel types that can be added are Central Tire Inflation Systems (CTIS). They can keep the tires continuously pressurized so long as the tire puncture or leak is not real large.
I am going to cover two methods of flat proofing pneumatic tires by removing all the air pressure from the tire. Polyurethane foam fill is a common method that most everyone knows about. But Trojan Tire Liners is not so widely known even though it has been around for many years. Each approach is different and has its own benefits and draw backs.
Polyurethane foam filled tires are completely flat proof, puncture proof and to a limited extent cut resistant. There are a large number of applications it is suitable for, size limitations, load and speed limitations and heat buildup issues. Foam filled tires are air-less tires so there is no air pressure to contend with. It is fairly easy to get set up to do tire foam filling. You just have to contact a polyurethane foam supplier and sign up, by the necessary equipment, buy the liquid polyurethane components you need, have a suitable environment to do the work, get trained on doing foam filling and start selling the service.
Foam fill for tires is also known as “tire fill” or “poly fill” and those terms can be used synonymously in the context to pumping polyurethane foam into tires for flat proofing. The use of polyurethane foam fills in tires has been around since 1970 so there is a great deal of experience with the product. Polyurethane foam fill for tires is composed of a two-part liquid polymer (Part A and Part B formulas) that is pumped into the tires through a specialized pump that blends the two components. In the pump the Part A and Part B liquid compounds are mixed and a chemical reaction begins to take place. Prior to pumping foam into the tire, the air is drained out of the tire and an air escape hole is drilled into the tire. This hole is later plugged when the tire is full of foam and has displaced all the air. The blended liquid material is pumped into the mounted tire/wheel assembly through the valve stem with a special foam filling pump and the air in the tire chamber is forced out of the tire. When liquid foam fill begins to come out of the air escape hole drilled into the tire, the hole is plugged and more foam mixture is pumped into the tire to achieve a required pressure rating. When the right pressure is achieved the valve hole is sealed. The polyurethane foam fill mixture then cures for 24 to 48 hours into a synthetic rubber-like core rendering the tire flat proofed.
Polyurethane foam fills come in different hardness ratings (durometer scale) for different applications where flat proofing is deemed necessary. The various manufacturers of polyurethane foam fills have their own unique formulations to achieve their hardness ratings. With the large variety of equipment types, applications for use, end user site specific conditions and other unique requirements that may be present, choosing the right durometer of foam fill is essential. Basically, there are four ranges of foam fill hardness:
In the last several years with the recognition of Green or environmentally friendly initiatives, manufactures of polyurethane foam products have come out with equipment to reutilize cured foam. For many years, once the tire in a foam filled assembly reached the end of its useful life, the worn-out tire and foam fill would have to be cut off the wheel so a new tire could be mounted and the assembly could then again be foam filled for reuse on equipment. In many cases the foam was disposed of as waste in a landfill.
Some commercial tire dealers would (and some still do) cut up the used foam into smaller chunks and put the chunks back inside of the new tire being remounted on the wheel and then virgin fill is pumped in the tire with the chunks dispersing throughout the foam. This process is known as “chunking”. The pros for chunking is that you need less virgin foam fill to refill the new tire assembly and therefore you save the customer purchasing the new foam filled assembly money. The cons for chunking is that it is the chunks are not consistent or uniform in size and are not dispersed evenly throughout the new foam filled assembly. There is no chemical bond between the chunked foam fill pieces and the new virgin foam fill. Friction between the chunks and the virgin foam fill creates excessive heat which will lead to premature foam fill failure. The chunks can lead to voids in the foam filled assembly and those voids can lead to flat spots forming or premature failure of the foam filled assembly due to the chunks moving inside the foam fill leading it to fracture and break down of the foam inside the tire. The biggest con for doing chunking is that the new foam being pumped into the new assembly IS NOT warranted by the foam manufacturer.
The better solution was arrived at by the polyurethane manufactures with the introduction of re-grind equipment. Re-grinder’s as they are known take previously used foam fill chunks and grind the foam into small pieces. In the new foam fill equipment with re-grind pumps, these small pieces of re-grind foam are blended back in again with virgin liquid foam fill and pumped back into the new tire/wheel assembly. The pros for using regrind are many:
The benefits of using foam fills in tires are many and there are a few cons.
Foam filled tires features
Pro’s – A flat proof tire!. Tires can be punctured, cut and chipped and the tire will not go flat and the equipment will continue to roll and do its work. Works in any tubeless or tube type tire with a sound casing. Will work in extremely adverse weather conditions even down to 70 degrees below zero Fahrenheit. Excellent heat dissipation qualities to reduce heat buildup.
No chance of a tire blow out causing instantaneous flats. Protects your operators, other workers or pedestrians in the work area from the explosive force of a blown-out tire.
Limited chance of equipment tip-overs due to operators losing control of equipment to due to instantaneous tire failure.
Increased weight and tire ballast in overload or applications were ballast is required or beneficial.
Limp-in capability. Severe tire damage won’t stop the equipment from moving to a safe stop location out of the work area.
Greater productivity due to elimination of equipment down time due flat or leaking tires.
Eliminate or greatly lower your tire repair costs. Flats and down time are expensive.
Retreading is possible to extend the service life of the foam filled mounted tire/wheel assembly (qualified retreader’s are necessary).
Improved tire life due to tires maintaining proper inflation and deflection on the work surface.
Reduction in lost wages and income due to equipment down time.
Typically, the cost of the foam fill will pay for itself the first time you need it. Except you may never know it until you stop the equipment to find your tires has a puncturing object stuck in it or the tires has been damaged such that a pneumatic assembly would have left you sitting idle.
Multiple ranges of foam fill hardness can be pumped into a nearly limitless variety of tires used in a very broad range of equipment applications. Remember no two applications are identical.
Polyurethane foam components Part A and Part B are composed of petroleum based chemicals and are subject to the price fluctuations of crude oil.
They add significant weight to the mounted tire/wheel assembly. A draw back if weight is an operational consideration. A benefit when increased ballast is desirable. Depending on the user or equipment owner, that weight may not be considered a disadvantage. They have to make the call.
A vast range of pneumatic tires are capable of being foam filled for use in an extensive list of applications.
Agricultural equipment and implements
Push back tractors
Tractors (Front and rear)
Ramp maintenance equipment
Trash removal equipment
Tree service equipment
Lumber yard equipment
Material handling equipment
Road building equipment
Sand and gravel equipment
Sewer working equipment
Skid Steer loaders
Golf Course Maintenance
Sod farming equipment
Surface and Underground Mining equipment such as:
Front end loaders
Other General Applications suitable for foam filling:
Golf Ball Retrievers
Rural Mail Trucks
Carts / Wagons
Ice Grooming Equipment
Compact Utility Loaders
Another approach to running pneumatic tires without air is using Trojan Tire, tire liners. Trojans tire liners are made from custom cut sheets of cellular rubber. These custom cut liners are cut to fit tires by tire size. The liners are installed into a tire one layer at a time. Once all the layers are installed inside the tire, the tire and liners are pressed onto the multi-piece wheel. One pressed on, the removable side flange is pressed down onto the tire and the lock ring is installed. The wheel is then ready to be installed on the machine. It is airless so it will not go flat.
These tires are completely flat proof, puncture proof and cut resistant. There are specialized applications it is suitable for, size limitations, load and speed limitations and heat buildup issues. They are air-less tires so there is no air pressure to contend with. You have to be an authorized dealer to sell or you have to buy from one.
Trojan Tire makes two kinds of liners. One is the “Reusable Heavy Duty Soft Core”® and the other is the called Tuffil® which is mostly for a one use installation.
The only way to get Trojan Tire liners is to buy them direct or from one of their authorized tire dealers. They want to make sure the product is used correctly in whatever application you have in mind.
Cellular rubber is different from hard rubber because it is created using gas developing agents which introduce air, thus making the material less hard and dense but more heat resistant and absorbent. Cellular rubber, in comparison to solid rubber has less density.
The two main varieties of “cellular” rubber are:
Open cell or sponge rubber has air cells that are open and interconnected to the neighboring cells. This pattern allows air and moisture to seep in easily, giving this rubber its absorbent quality and the ability to regain its physical form after compression.
Closed cell or expanded rubber which doesn’t allow the seepage of fluids. This rubber is cheaper and has the ability to stay afloat in water which can’t violate its structure.
Cellular rubber is a modern miracle and can be defined in terms of other specifications like ability to absorb shock, floatation capacity and fluid immersion. Cellular rubbers range consists of a large number of qualities with many different properties. Cellular rubber is black foamed rubber material with closed cells.
Air-Like Ride: Air-Cell Rubber is Shock Absorbing to Operator and Machine. This means happier and safer operators and Reduced Maintenance Costs.
Strong for Long Tread Life: Manufactured from real cellular rubber that is much stronger than polyurethane. This means longer tire life because will not easily breakdown under higher loads and speeds – leading to premature tire failure.
Best for the Environment:
One additional benefit is they provide better protection against tire sidewall cuts than does polyurethane foam fill. In the event of a large tire sidewall cut where the foam fill is exposed, foam fill does not have the density to hold together. Over time with continuous movement the foam fill will break down and you will not have the benefits of a foam filled tire. Trojan Tire liner will continue to work because of their design. Not ideally of course, but at least you can get your machine to a service area to get the tire changed.
You will find Trojan Tire liners in use at many of North America’s leading Underground Coal Mining Companies in their fleets of scoops, battery haulers, shuttle cars and support equipment. Trojan’s patented liners help to increase the tire’s load capacity by up to 50% over air, which is an ideal feature to help these specialized machines in these harsh environments to achieve their production targets in a safe and sound manner.
Coal miners are serviced via Trojan’s Dealer Network. Trojan dealers receive extensive service training and sales support on how to best market and apply the Trojan products for best results and lowest costs.
Coal machine Original Equipment Manufacturers fit their machines with Trojan Tire liners at the factory level. Trojan offers unique solutions to OEM’s and the aftermarket as well as technical advice to help you select the best tire options for your operation.
Trojan Soft Cores are widely accepted as the best fill medium for radial tires to get the maximum performance and longevity out of a radial tire. Higher quality bias ply tires get an air like ride with Trojan’s soft riding real cellular rubber compounds.
Using Trojan’s tire liner technology to replace the air inside a tire eliminates any explosive force potential you could possibly experience with pressurized air. Trojan Tire liners are promoted “ideally for confined space underground mine applications – giving your operators a more healthy and safe work place and yielding higher performance. Implementing safety programs help to reduce management liability exposure.”
Trojan Air-Cell Technology helps your tires to have an increased load capacity, in the range of 25% to 50% depending on bias or radial construction.
Trojan Tire liners are only made to fit certain sized tires. They have a pretty large range of common sizes available. If you have questions about tire liners to fit the tires you want to flat proof you need to contact Trojan Tire or one of their approved dealers for more information.
Trojan Tire Inc. is the Manufacturer of Patented Trojan Air-Cell® Rubber Tire Fill Technology.
Solid rubber tires come in two main types. The press on variety and the molded-on variety. One more kind of solid tire we will look at is the semi-pneumatic tire. Another offering that has been around for over 20 years is the “segmented tire”.
Solid rubber tires are also referred to as “cushion tires”. Solid rubber tires are completely flat proof, puncture resistant and cut resistant. There are however some size limitations, issues with loads and speeds and heat buildup. Since rubber is so dense, these types of tires can also be very heavy. So depending on the application involved, that weight can be an advantage or a disadvantage.
Solid rubber tires are also very expensive compared to pneumatic tires since rubber is not cheap. But when it comes to a cost of ownership, the cost comes down because they will last 4 to 8 times longer than a comparable foam filled tire.
Solid rubber tires offer many benefits because they are completely flat proof, puncture proof, cut proof and snag proof. They work very well in many extreme and abusive applications, but not well at all in others. Solid rubber tires have little shock absorption like you will find in pneumatic tires. In applications where machines and operators are maneuvering over uneven ground or rolling over obstacles at more than creep speeds, the machine and operator will be subjected to a lot of shock and vibration. Solid tires have very little give. Manufacturers of solid rubber tires have invented tires with “aperture’s” molded into the tire side walls to give the tires some “give” or cushioning. Each manufacturer has their own benefits as to why their aperture design is better. These aperture designs can come in a single ring of holes to multiple rings of holes spaced in different patterns around the tire. Manufactures have some up with different sizes of holes, oval holes and triangular holes. Each with their own performance benefits.
Long term use and exposure to all the extra shock and vibration resulting from using solid rubber tires on a machine can lead to additional and unexpected equipment maintenance. There is also the issue of “whole body vibration” which over time can cause health issues for operators of heavy equipment equipped with solid rubber tires.
In applications where the working surface is smooth and hard, solid rubber tires on a machine will work very well. Applications such as solid waste management where the machines will be operating on concrete or asphalt surfaces. They also are work very well on machines that go slow and lift very heavy weights like transfer trailers that move heavy materials from place to place. One example is on certain kinds of underground mining equipment. You will also find them in junk yard and scrap yard applications on equipment that is mostly stationary but must be moved on occasion like Sennebogen material handling machines. You will also find them in demolition, road building and construction applications.
Pressed on solid rubber tires come in two varieties as well.
You will find “pneumatic shaped tires” made to fit standard wheel or rim profiles and sizes. But you will need a tire press to push these tires onto the wheel. Not all tire shops have access to these tire presses.
You will also find solid rubber tires that are molded onto a steel band. Those solid tire tires are then pressed onto custom wheels that are then mounted onto the vehicle. These are commonly found on many kinds of forklifts.
There are also special wheels that have solid molded rubber on them. These are found on a several kinds of industrial equipment as well as aerial work platform scissor lifts.
There are now several companies that are making pneumatic shaped tires that are pressed on conventional wheel and rim sizes. These companies are now offering swap out programs for owners of large heavy equipment. All you need to do is call them up, tell them what machine you have and they will ship you a solid rubber tire mounted on a wheel assembly that is ready to be mounted on your machine. The owner of the machine just changes out the air-filled assemblies on their machine and replaces them with the new solid tire assemblies. The air-filled assemblies are then shipped back the company that supplied the solid tire assemblies so they can be used in their swap program for solid tires.
Manufacturers of the press on tires use different types of tire core constructions as well as aperture designs to give the tires a more cushioned performance characteristic.
Molded on rubber tires are available for a wide range of heavy equipment from forklifts, wheel loaders, rubber tired dozers, yard cranes and a whole host of other industrial equipment. These molded-on rubber tires and molded to custom sized wheels and the rubber is applied in varying thickness specified by the customer. One the rubber is molded to the wheel and then vulcanized in an autoclave, customized tread designs can be cut into the tread face or they can be left as a smooth tire. When being purchased for large equipment like wheel loaders you will be removing the existing tires and wheels and must buy custom built wheels made just for molded solid rubber tires. Not always in inexpensive proposition.
These tires can be manufactured with special formulations of rubber in layers that produce tires with special qualities to offer outstanding cut, chip and wear resistance. Then can be molded in a wide range of widths for custom wheel sizes.
Manufacturers capable of making molded on solid tires can custom build special tire/wheel combinations. All you have to do is ask if you have some special need.
Molded on rubber tires can be recapped as well. Then the rubber has been worn down or severely damaged the wheel/tire can be taken out of service and sent back to the factory to be rebuilt.
There are many companies around the world that make solid rubber tires so finding them is not difficult.
Semi-pneumatic tires are solid rubber tires but they are hollow in the middle. They are designed to operate without air. They are made with very thick sidewalls and tread face. They must be pressed on a special wheel and then can be used on a machine. The most common application for these tires is for lawn moving equipment. You will find them in use on several zero turn mowers on the from tire positions in front of the mower deck.
Segmented tires are a special application of tire. These are special wheels with segments of tire tread that are bolted to the outer surface of the wheel. These tires and wheel are still in use and can be purchased from SolidBoss. These tire/wheels and segments are available in non-marking gray rubber and regular black rubber.
The main benefit of these tires and wheels is as the sections of the tire are worn down or damaged enough that they need to be replaced, the bad segment can be unbolted and replaced. Common applications where you may see these tire/wheel designs in service are aerial work platforms and boom lifts.
Polyurethane tires are found in two types. The press on and the mold on type.
These tires are completely flat proof, puncture proof and cut resistant. There are specialized applications they are suitable for, size limitations, load and speed limitations and heat buildup issues. They are air-less tires so there is no air pressure to contend with.
The forklift and indoors material handling industry is very dependent on polyurethane or “poly” tires and wheels. Poly tires have been widely used for over 50 years now. Poly formulations have a range of strengths and weakness unique their chemical makeup. Polyurethane has a much greater load carrying capability than do rubber tires. Typically, that load carrying capacity of a poly tire is twice that of a rubber tire. Poly is mostly relegated to applications that are indoors and where the machine that uses them operates on smooth concrete.
Polyurethane has a very low rolling resistance compared to rubber. Poly tires are ideal for applications like electric lift trucks or fork trucks.
Polyurethane is much harder than rubber so these types of tires and wheels have little to no cushioning. You won’t see many machines operating outdoors on polyurethane tires because of the lack of shock absorption.
Since polyurethane is so hard it doesn’t have much traction ability to grip the surface it is operating on. The surface should be clean and dry for optimal performance.
Poly tires have a very high wear and abrasion resistance. Typically, a poly tire will outlast a rubber tire by about four times. They also have very high cutting and tearing resistance. They also will not mark floors like rubber tires will.
Polyurethane tires and not well suited for continuous high speed operations since they don’t dissipate heat very well. Will rubber on the other hand dissipates heat very well.
One advantage that poly tires have over rubber chemical resistance. Rubber tires exposed to certain kinds of solvents will break down or wear much faster. There are certain kinds of very harsh solvents that will destroy polyurethanes as well.
Press on polyurethane tires and steel bands where the poly material has been molded to the band. These bands come in a wide range of sizes, poly durometers, colors, tread designs, poly depths, widths, diameters and are ready to be pressed onto the machine wheel as required.
Molded on polyurethane wheels are custom made wheels with the polyurethane molded to them. Typically, you see a manufacturer of piece specialized equipment have a custom-made wheel that needs the specific design, be it a proprietary nature or some other engineering requirement, and you must buy that wheel only. There are some poly wheel manufacturers that make a wide range of standard wheel designs that are used across industry. You may have to do some digging to find what you need.
The Tweel is completely flat proof, puncture proof and cut resistant. There are specialized applications that it is suitable for, size limitations, load and speed limitations. They are air-less tires so there is no air pressure to contend with.
Michelin’s engineers in 2005 came out with their invention called the Tweel. Tweel is short for a tire and a wheel. It won several design awards after its introduction. The unique design of the Tweel also got other companies busy creating designs to compete with the Tweel. We will look at some of those under Variants. Click here to read a more detailed explanation of the Tweel.
Benefits of the Tweel design are that it is airless, can be made with multiple tread design features, is recapable, is very useful in applications for vehicles like mowing equipment that don’t have shock absorbing suspension systems.
Since the introduction of the Tweel other variations on the idea have come to market. They are mostly niche specific products designed to certain applications.
Let’s look a couple.
The Non-Pneumatic Tire (NPT) by Resilient Technologies. Click here for more information and to see videos of the NPT in action.
The NPT was developed for the U.S. Army to use on High Mobility Multipurpose Wheeled Vehicle (HMMWV or Humvee). They are airless tire and wheel assemblies that can’t get shot out by a bullet or shrapnel for a road side bomb.
Non-Pneumatic, Non-Solid Wheel
Big Tyre in Australia is developing non-pneumatic, non-solid wheels for underground heavy equipment in association with, and significant financial support from, the Australia Coal Association Research Projects (ACARP). Click here for more information on the unique wheel design.
Bridgestone Tire has gotten on the bandwagon too with their version of air free puncture-less tires too. Click here to read more.
The end. At least for today. Wow. We have gone on a journey. There is a lot more that could be said about flat proofing pneumatic tires, puncture resistant tires and solid rubber tires. Check back for more interesting articles and blog postings about off the road tire and wheel products. I have much more coming.