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22 Jan

TrailerTech: Trailer Blocks Safety Questions and Tips

Welcome to a new installment of TrailerTech! Today, we’ll take a look at some questions and comments lately that we’d like to address.

The proper installation of our products is of major concern for us and as such, we actively strive to aid our customers with any technical or safety-focused questions they may have. Inquiries such as “Are lift/lowering blocks safe for use on my trailer?” have made their way into our inbox and we’d like to offer some information and tips on some common concerns we’ve seen raised.

Changes in Vehicle Height

Changing the height of a vehicle will always change vehicle dynamics, period. We have assembled some tips for lifting and lowering your trailer.

Lifting: Despite raising the trailer’s center of gravity, it’s important to note that a level trailer is far more stable than a low, but improperly leveled trailer. 1”- 4” blocks will keep the change in overall ride height small and minimize the added mechanical advantage the axle has on the suspension. A rule-of-thumb to use when working out an appropriate lift is to keep the ride height change within 5% of the overall vehicle height. For example, adding a 3” lift to a 10 ft. tall travel trailer would result in a 2.5% change in the ride height, which is acceptable.

Lowering: When lowering a trailer, clearance becomes the major factor. Once again, 1”- 4” blocks will minimize the added mechanical advantage the axle has on the suspension. Generally speaking, a standard trailer suspension will accommodate 1” – 2” blocks without modification. When lowering a trailer 2.5” – 4” it is advisable to switch to a standard 4” drop axle, and adjust up or down with blocks and axle placement (above or below the spring) to achieve the desired ride height.

While discussing changes in vehicle height, we talked about the added mechanical advantage the axle has on the suspension with the additions of lift/lowering blocks. This can be broken down into two categories: axle wrap and wheel scrubbing, explained below.

Wheel Scrubbing (lateral twisting)

Wheel scrub is fairly common in tandem axle situations. Since the center of mass is between the axles, maneuvering a trailer in a tight area causes it to rotate on its axles. One axle shifts to the left and one to the right, causing the axles to appear misaligned. This situation is present on trailers with or without modifications to the ride height. Wheel scrub can look unnerving, but leaf spring suspension is well suited to dealing with this due to its excellent lateral rigidity. It’s important to remember that the forces the suspension encounters under hard braking are actually greater than those encountered during wheel lockup or wheel scrub. A locked wheel behaves in a similar manner to a wheel in scrub, in that they are both not rotating with respect to the road with low friction between the contact patch on the tire and the road surface.

Axle Wrap (longitudinal twisting)

Axle wrap, or longitudinal twisting of the leaf spring occurs when torque is applied to the suspension, forward or aft, in the form of acceleration or braking. It is the leading cause of concern when using blocks on a driven axle or, the front axle of a vehicle, as the block can “squirt” out under extreme torque. The axle is not driven on a trailer and the condition known as axle wrap does not occur under acceleration under normal circumstances. But trailers have brakes, this means the axle is subjected to axle wrap under braking. Tires on an axle that is not driven and not the front axle of the vehicle, experience wheel lock-up before axle wrap overwhelms the spring. This means that the maximum amount of axle wrap occurs at impending wheel lockup. The leaf spring by design is well suited to absorbing forces acting longitudinally on the spring. Adding suspension blocks to a trailer will increase the effects of axle wrap caused by braking. Increases in axle wrap, wheel scrub and changes in vehicle height, are non-issues when adding lift and lowering blocks to trailers using axles with a gross axle weight rating (GAWR) of 3000lb to 7000lb as long as you follow some simple guidelines:

  • Use only SAE Grade 8 U-bolts with rolled thread.
  • DO NOT re-use U-bolts under any circumstance. If re-used, 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, they will fatigue, break and fall off.
  • U-bolts must be torqued to the manufacturer recommendation. If U-bolts are under-torqued, they may loosen. If U-bolts are over-torqued, they can exceed their ultimate tensile strength and break.
  • Carefully assess tie plate wear, it is 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.
  • Use only solid billet aluminum Trailer Blocks that will resist crushing forces.
  • Always ensure that springs, spring clips, shackles, suspension bolts, bushings, and mounting brackets are in good, lubricated condition (up to date in the case of a dry system) and are free from corrosion.

Maintaining these components with regular upkeep is as important as any regular trailer maintenance routine with or without ride height modifications.

By following the above guidelines, lifting or lowering your trailer with blocks is a safe and effective way to modify the ride height of your leaf spring trailer. It ensures your rig is kept level, and it opens up a diverse selection of wheel and tire options to improve on and off-road performance.

We got hope this helps clears up any questions or concerns. If you have any technical issues of your own you’d like us to talk about, please send them to: contact@trailerblocks.com

More entries and updates coming soon.

11 Jan

TrailerTech: Stainless Steel Fasteners in Steel and Aluminum

Welcome to the first installment of TrailerTech!

We’re launching this new addition to the blog lineup to share some technical details, facts and tips that can help you with your trailer performance endeavors. Today, we’re covering a common misconception that we’ve seen crop up over the Internet. According to some, stainless steel bolts aren’t necessarily a good idea to use in carbon steel or aluminum beams due to the process of galvanic corrosion. Our team has observed a few things during some in-house testing and we’d like to take a minute and help clear up some misconceptions.

Galvanic (or bimetallic) corrosion occurs when two different kinds of metal come into contact and are exposed to an electrolyte (rainwater, groundwater, mud, saltwater etc.) which causes an electrochemical reaction. When this electrical process occurs, one metal acts as an anode and the other as a cathode. As a result of the galvanic connection, the anodic metal decays at a much faster rate than it normally would and the cathodic metal decays much slower. Eventually, this connection causes the anodic metal to dissolve and deposit its remains upon the cathodic metal, causing rust to form.

So how big a deal is galvanic corrosion when using stainless steel hardware to fasten stuff to your trailer's frame?

To test this in-shop, we chose 300 series stainless steel due to it's high availability and common use as a fastener. We observed that although the galvanic connection is still made with electrolyte exposure, the shear size of the anode (the ample frame) greatly decreases the rate of decay. In fact, no galvanic corrosion was detected. Overall, we have found the effects of galvanic corrosion of 300 series stainless steel in carbon steel or aluminium to be greatly overstated, and consider the practice to be safe. The key understanding being that no rust is formed due to the small relative size of the stainless steel fastener within the larger piece of carbon steel. For extreme duty applications, such as continual salt bombardment during the winter time, prolonged use in saltwater or prolonged exposure to mud, a zinc chromate primer can be applied prior to assembly with stainless steel fasteners.The frame should be coated first, let dry, then the fastener coated and inserted wet. It would seem that the benefits of rust-resistant stainless steel hardware for trailers greatly outweighs the infinitesimally small risk of galvanic type corrosion.  

We hope this has provided you with some insight into using stainless steel fasteners in carbon steel or aluminium. We have more informative topics lined up, so keep an eye on the blog.

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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