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29 Jan

TrailerTech: Aluminum vs. Solid Steel

Welcome back for our latest TrailerTech article!

Today, we’re taking a look at something that’s been brought to our attention before: why do we use 6061-T6 aluminum for our lift/lowering blocks as opposed to solid steel? This is not the first time alternative materials and composition methods for Trailer Blocks have been discussed (see our previous article here), but since we’ve had some questions regarding the use of solid steel for blocks, we’d like to reexamine the issue here.

A Trailer Block fabricated from solid steel such as billet steel, has a compressive strength capability as high and depending on the alloy, higher than a Trailer Block fabricated from 6061-T6 aluminum. We can see strength is certainly not the issue, but what about weight? A Trailer Block composed of solid steel will add a relatively large amount of unsprung mass to the axle. When a leaf spring breaks, this can often be caused by a sudden unloading of weight, such as when a wheel drops into a hole in the road. In a situation such as this, unsprung mass is often the biggest culprit. A large increase in unsprung mass caused by a solid steel block would require a custom spring designed to accommodate the extra mass. If the trailer is not equipped with proper shock absorbers, the effect can be even greater, causing more suspension oscillation over bumps. To reduce the amount of unsprung mass, aluminum remains the ideal alloy to fit the technical demands of the application due to its strength to weight ratio and corrosion resistance.

We also recommend that you consider the following points when lifting or lowering your trailer with our signature Trailer Blocks:

  • Use only solid billet aluminum lift/lowering Trailer Blocks that will resist crushing forces
  • Use only SAE Grade 8 U-bolts with rolled threads.
  • Do NOT re-use U-bolts under any circumstances. When reused, U-bolt clamping force is reduced by over 55%, even though your torque wrench reading is identical. U-bolts should never be used with lock washers, as they will fatigue and eventually break.
  • U-Bolts MUST be torqued to the manufacturer’s recommendation. If U-bolts are not torqued sufficiently, they may loosen and if they are over-torqued, they can exceed their maximum tensile strength and break.
  • Carefully asses tie plate wear. It’s generally a good idea to replace tie plates every time you replace U-bolts. Ensure the tie plate is strong enough to support the required U-bolt.
  • Always ensure that springs, spring clip, shackles, suspension bolts, bushings and mounting brackets are in good, lubricated condition (up-to-date in the case of a dry system) and are corrosion-free.

Thanks for reading.

18 Dec

Trailer Tech: Cambered Axles

Welcome to a new installment of Trailer Tech! This entry, we’re taking a look at the importance of cambered axles and how this can affect your lift/lowering endeavors.

Camber refers to the measurement of a vehicle’s wheels vertical alignment with the ground. The camber angle can have a profound impact on a vehicle’s handling, as well as the grip and overall lifespan of the tires. If the bottom of the wheel sticks out further then the top, this is called a “negative camber”. On the other hand, when the top of a wheel sticks out further than the bottom, this is a “positive camber”. Most trailer axles come with a slight arc in them by design, allowing them to compensate for any unwanted cambered angles while bearing the weight of the vehicle and keeping its wheels straight. These angled axles are also known as cambered axles (pictured below),

The axle pictured above is oriented correctly for both the lowering state (suspension pictured in front) and the lift state (suspension pictured in rear). With weight applied to the suspension, the arc in the axle straightens and the wheels stay straight.  Consider that if a cambered axle such as the one pictured is rotated 180 degrees while retaining the current suspension orientation, it would cause a positive camber angle when the weight of the vehicle is applied. Positive camber angles are particularly unsafe as this position reduces the tire’s contact with the ground, reducing overall grip and increasing wear and tear.

If an axle is being transitioned from a lowering state to a lift state or vice-versa, spring seats opposite of each other are required so that the axle can remain in the same orientation.

Thanks for reading.

21 Aug

TrailerTech: Reusing Tie Plates

Welcome back to TrailerTech!

We all know you shouldn’t re-use u-bolts when servicing or modifying your trailer’s leaf spring suspension. Tie plates though, aren’t as cut and dry. There are obvious qualitative observations that can be made, such as the presence of rust or total failure. Structural integrity is a much different story. At a casual glance, tie plates often appear unchanged after a use or two. In this TrailerTech article, we’ll take a closer look.

Lateral bending is one of the biggest concerns when assessing a tie plate’s structural integrity. The tie plate flexes across the leaf spring, bending towards the u-bolt’s clamping force. The photo below shows an unused tie plate on the left and a tie plate torqued down only once on the right. Notice the slight circular markings from the u-bolt washers.

A keen eye will also notice the slight arc in the tie plate on the right (a 1mm rise). This might not seem like much, but if we graph the result, the deflection is much more apparent.

Naturally, the proper care must be taken when re-using tie plates, as lateral bending is not always visibly obvious and a closer inspection is necessary. If you have any doubts about your existing tie plates, the safest thing to do is to replace them along with other one-time use parts, such as u-bolts.

We hope this TrailerTech article is helpful when making your assessment.

17 Oct

Trailer Tech: Car and Truck Tires On Your Trailer

Welcome to Trailer Tech!

The winter season is quickly approaching and snow and ice will soon coat the roads (and off-roads). We here at Trailer Blocks thought it’s the perfect time to talk tires. Many folks assume that the trailer tire or “ST (special trailer)” tire is the only option. This simply isn't true.

A unique characteristic differentiating the trailing vehicle from the driven vehicle is trailer sway. One of the primary causes of trailer sway is flexing in the sidewall of the tire.  For this reason it is critical to choose a tire that carries a sufficient load index for the trailer. For example if your trailer’s GVWR is 6000lbs and is tandem axle, the tires should be rated for 6000lb / 4 tires = 1500lbs per tire.

Referencing a tire load index table, such as the one found here: http://en.wikipedia.org/wiki/Tire_code#Load_index tells us that an ST (special trailer) or LT (light truck) tire would need to carry a load index code of 95. If we were putting P (passenger car) tires on the trailer we would have to apply a 9% reduction resulting in a load index of 99. This is because ST and LT tires carry a ply rating, while P tires do not.

By correctly matching a tire’s load index to the trailer’s requirements, P and LT tires can be used on your trailer. This opens up a lot of options.

In vehicles, we select a tire that is appropriate for driving conditions, the trailer is no different. Off road driving demands an off-road tire with multiple plies and a high load index. An aggressive tread pattern is useful to prevent sliding on uneven terrain. On-road street driving demands a high speed rating with a well-designed tread pattern for good wet/dry performance and cornering. Tires with V-shaped groves help relocate any potential road water from the center of the contact patch to the outside, preventing hydroplane condition. Winter driving conditions warrant winter rated tires that remain soft and sticky on ice where trailer brake performance can be devastating.

Overall, maximizing the speed rating for the load index required yields the best results. A high speed rated tire has a superior tread pattern and a correct load index greatly reduces trailer sway.

In any case, tire balancing is important and on-vehicle balancing can remove a lot of secondary ride issues (such as vibration).

Check back next time for more trailer tech talk.

14 May

Trailer Tech: Aluminum Billets

Welcome to Trailer Tech!

Today, we're going to be kicking things off with a topic that we've discussed among ourselves and was subsequently submitted to us from an anonymous reader. We're going to be talking about why we use the kind of aluminum we do and why we don't pursue alternatives.

Billet Aluminum Trailer Blocks group image

Our lineup of signature 6061-T6 Aluminum Lift/Lowering Blocks

Since we started production, our aluminum lift/lowering blocks have been from 6061-T6 aluminum billets. Although we stand by the use of billets, there has been something of a debate as to whether or not it's worth investigating the possibility of using cast metal instead. After careful deliberation, we ultimately found far too many potential issues that can arise from a cast metal block and the stability of a solid billet was unparalleled for our use. Structural defects are more likely to occur during the casting process; such as the presence of inclusions (foreign materials cast into the metal), lower elongation and shear strength as well as random soft spots along the finished product, leaving the final block more brittle as a result. It goes without saying that a brittle product has no business being attached to your trailer, so we actively avoid using cast parts in our process.

Billet aluminum, on the other hand, is far more effective at keeping inclusions or other potential errors at bay. As its being created at the mill, the billet is continuously cast using rollers which help ensure a uniform size while keeping the metal effectively free from inclusions or other defects. We wanted to go one step further ensuring the block's overall strength, so we decided on the T6 aluminum mainly due to its tempering process. T6 is tempered via a method known as "precipitation hardening" which increases the yield strength of the aluminum. As it's been allowed to settle uniformly, the precipitates in the metal impedes the movement of dislocations which are generally where deformations are found, Upon completion of the hardening, the finished product (billet) can be nearly twice as solid as cast aluminum. In the end, we're left with a more stable product to use and craft.

We've also noticed that many lift/lowering blocks being used today tend to have large, milled out sections in them, often in the name of reducing overall weight of the block. While there might be some merit to this method, we have found that cutting out sections of an aluminum block reduces the overall structural integrity and undercuts its potential strength far more than it's worth. Lift/lowering blocks need to withstand tremendous force and weight at all times of use and we feel that there just isn't a call to cut corners where it doesn't need to happen.

Ultimately, using the 6061-T6 aluminum billets for our blocks makes the most sense as it is a strong, uniform metal that ensures a better product and reduces the potential risks that come with alternative methods.

We hope you've enjoyed this entry of Trailer Tech and the insight into our metal choices. If you have any suggestions for topics or any feedback, feel free to send it in to: contact@trailerblocks.com

Thanks for reading!

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