Technical Articles Relating To Off-Road Vehicle Development

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JD2 Model 4 Tubing Bender: Part 1

Published by Trails Less Traveled on November 1st, 2006

 

Introduction to Tube Bending Methods & Equipment

This is the first installment in a series of tube bending-related articles that we’ll be publishing in The Chop Shop over the coming months. Just like the welding articles, we’re going to cover the basics and then move into the more technical stuff. Let’s start by taking a look at different tube bending methods and types of equipment.

Ram benders are most often used for bending light-gauge materials like electrical conduit and exhaust tubing. They bend material from the apex of the bend outward and produce a visible amount of deformation through the bend area. The kinking at either end of the bend and the changes in the shape of the cross-section compromise the tubing’s strength and make this bending method unacceptable for structural applications. Bottom line: don’t have an exhaust shop bend your rollcage tubing.

Most automotive fabricators are using some type of compression tubing bender. There are many different variations on the basic design, but they all have a few important elements in common. The tubing is held in position by the Clamping Die and is pulled around the Forming Die by the Pressure Die. The material is still being compressed and stretched through the bend, so some deformation is inevitable, but it should be difficult to identify without measuring the tube or cutting a cross-section of the bend and the strength is not compromised nearly as much as with a pipe bender.

Many people refer to rotary-draw benders as mandrel benders, but that’s not exactly right. A mandrel is actually an additional part of a rotary-draw bending tool set that is inserted into the material before bending (and removed afterwards) to further reduce any visible deformation through the bend area. It is also possible to achieve tighter bend radiuses when using a mandrel (compared to a regular rotary-draw bender). Mandrel-bent exhaust tubing is the most common application for this process in automotive fabrication, where smooth bends and flow restrictions are critical. Mandrels are not commonly used when bending tubing for structural applications because although the bends looks flawless, mandrels do not improve the structural integrity of the bend. Van Sant Ent. notes in their description of the mandrel bending process, “the outer wall of the tube is actually stretched thinner by the mandrel bending process.”

A ring-roll bender is the right tool for the job when you want to bend a large radius in a piece of tubing to follow a curved windshield or cradle a spare tire, but they can’t bend tight enough radiuses to be practical for the majority of automotive fab work.

Manual or Hydraulic

There are a number of companies producing different tubing benders and there are substantial differences in features, performance and price. So what should you look for when shopping for a tubing bender and how much should you spend? Well, first of all, it’s important to point out that bend quality is determined by the quality and placement of the dies more than any other aspect of a rotary-draw tubing bender’s design.

So does that mean a $295 JD2 Model 3 manual bender can produce the bends just as nice as the $2,315 JD2 Model 4 electric/hydraulic bender because the dies are interchangeable? Absolutely. That’s why good dies aren’t cheap.

Then why spend all that extra money on a hydraulic tubing bender? Just like anything else, you’re paying for speed and convenience (video clips of JD2 Model 3 vs. Model 4).

If you’re only planning to use it infrequently, a manual bender will pay for itself quickly and is probably your best option. Depending on the type of manual bender you purchase, it may be possible to upgrade to hydraulic power later. A quick search in Pirate 4×4’s Tool and Shop forum for ‘hydraulic bender’ will turn up all kinds of information on this topic that will help thrifty shoppers put together an affordable hydraulic-powered bender. If you’re looking for more of a turn-key conversion package, Van Sant also sells all of the parts required to add a hydraulic ram to the JD2 Model 3 bender. But JD2’s hydraulic-powered Model 4 only costs about $275 more than a JD2 Model 3 bender after you buy all of the hydraulic conversion parts (comparison prices from Van Sant Ent. include all hydraulic conversion parts, hydraulic ram and electric/hydraulic pump).

Comparison Shopping for a Rotary-Draw Tubing Bender

Here’s a short list of some of the most popular rotary-draw tube bending equipment available. Take a look at some of the different design features and prices; there’s a pretty wide range between the entry-level and production-quality machines.

  • Lowbuck

    For my money, JD2’s Model 4 bender is the sweet spot. It’s a professional-quality bender and a substantial investment, but the overall design is really well thought-out and the bend-quality is second-to-none. There’s not another bender in this price range that I would rather purchase or use.

    I ended up ordering a JD2 Model 4 bender deluxe kit from Van Sant Ent. that included the Model 4 bender, a 10-ton 14” stroke single-acting hydraulic ram, a 1.5hp electric/hydraulic pump with hand remote and Van Sant’s own rolling pedestal for the Model 4 Bender.

    This was the first time I’d purchased anything from Van Sant and it was a really good experience. Their website was informative and easy to use. Their sales staff was knowledgeable and helpful. Their prices were competitive and they had everything I ordered in stock, ready to ship. My order arrived complete and correct, sooner than I expected it. I couldn’t ask for much more in a vendor and it’s a shame that so often we have to settle for less.

    Setup

    instruction manual=
    Assembling the Model 4 bender is fairly straightforward. After flipping through the instructions (available as a PDF Here), it only took about 1/2 an hour to set up our new bender.

    packaged bender stand=

    set-screw detail=

    assembled bender stand=

    The Model 4 bender weighs close to 170 lbs with the hydraulic cylinder, so we assembled the rolling pedestal before unpacking the bender. That went quickly because the three legs are each tightened into place with a single allen bolt. The pedestal incorporates a mounting plate for the hydraulic pump as well as a die rack that accommodates up to three complete die sets. The front wheel also has a lock on it to keep the bender from rolling around the shop when you’re using it.

    packaged bender frame plates=
    All of the parts were very well packaged and arrived in excellent condition (and that’s not something to take for granted with large, heavy objects). This picture on the right shows all of the bending plates and hardware after being unpacked.

    JD2 base plate=
    The steel base plate is 3/4” thick and the CNC-machined degree marks are nearly 20 inches in diameter, which makes them very easy to read at about 3/16” apart. The flimsy pinwheels and adjustable pointers on other benders just don’t compare to the integrated degree wheel on the Model 4.

    shimming bender stand= JD2 base plate installed=
    These supplied washers are positioned in between the mounting plate and the pedestal to ensure that the drive pins can be inserted all the way though the base plate. The bolt-heads are recessed into the base plate and the nuts are tightened from underneath.

    misc JD2 bender parts= JD2 bender arms=
    All the 3/4-7/8” thick steel links are CNC machined and the tolerances were right on. Living on the coast in Santa Cruz, CA, I wished there was some type of protective coating on these parts. I had to keep the bender and dies oiled down with a light coat of WD40 in order to stop it from rusting. But I haven’t had any more issues with corrosion since we moved up to Bend, Oregon.

    squaring the die-pins and bender frame plates= frame plates installed=
    The frame bolts are 1” in diameter and the steel frame sleeves are 1.5” in diameter to keep the whole assembly rigid. We installed the 1” frame pin and used a small square to align the holes before tightening-up the hardware.

    swivel-block detail=
    The hydraulic cylinder mount (swivel-block) is a CNC-machined steel block that pivots exactly at the cylinder’s center to eliminate any side-loads on the ram, which are hard on the bearings and seals. In contrast, the swivel-block for the Model 3 hydraulic conversion has to pivot off-center because of the way it’s adapted to the manual bender.

    spring-back lever installed =
    Next, we sandwiched the swivel-block between the upper and lower frame plates and bolted them together, but didn’t tighten the hardware. Then we installed the anti-springback lever.

    tightening frame-plate hardware=
    After sliding the drive-pin through the completed assembly to verify that everything was properly aligned, we tightened up the hardware. The locking ratchet mechanism keeps the workpiece under tension through the bending process so the ram can be advanced to the next stroke position without needing to reposition the workpiece.

    pusher-block detail= pusher-block detail=
    The pusher block is designed to eliminate cylinder side-loading and employs a bronze wear-block to distribute the bending force from the ram through the 1” diameter bolt to the base plate evenly.

    hydraulic ram installed= pusher-block installed=
    After unpacking the 10-ton, 14” stroke, single-acting hydraulic ram, we threaded the cylinder body into the pivot-block and then threaded the pusher block into the cylinder shaft.

    hydraulic pump detail= control detail=
    The 1 1/2hp electric-powered hydraulic pump adds about $800 to the price of the Model 4 bender (compared to the air-powered hydraulic pump), but it’s self-contained and doesn’t require an air compressor. The electric-powered hydraulic pump is also noticeably faster than the air-powered alternative. The yellow object in these pictures is the handheld remote control. It has a 5 1/2ft lead, so you can move around the bender and workpiece while bending, which is especially useful when you’re bending tubing by yourself.

    hydraulic fitting detail= quick-release fiting at hydraulic ram=
    One end of the hydraulic hose is threaded into the pressure outlet port on the hydraulic pump and the other end is attached to the ram with a quick-release fitting. I just filled-up the reservoir with hydraulic fluid, plugged the pump into a 110V power outlet and fired it up. The hydraulic components supplied by Van Sant are well-matched to this system and the speed/performance has lived up to the claims made on JD2’s website:

    Using a 14” stroke cylinder, the first bend stroke can be up to approximately 60 degrees. The second stroke will go to approximately 126 degrees. Bending speed is dependent upon the strength of the material being bent. Usually 6 to 10 degrees of bend per second will be realized. The 14” stroke cylinder takes 8 to 9 seconds to return from full extension. Add it all up and a typical 90 degree bend will take an effortless 20 to 25 seconds, depending on the operator’s skill level.

    Dies

    bender assembled with die-set=
    All JD2 Model 4 die sets are CNC machined from solid steel billets and will bend a complete 180-degrees. The pressure dies have replaceable shoes, which are made out of a proprietary bearing-grade alloy (they swear it’s not aluminum). We’ve been using these dies with a variety of lubricants to see what works best, but they don’t even mark the tubing when we bend (clean!) material completely dry. Our dies don’t show any signs of wear yet, but the shoes only cost about $35 to replace a set when they wear out. Van Sant also offers Delrin dies sets for applications where surface-finish is especially critical (like stainless steel tubing).

    Die sets need to be purchased for each size and type of tubing that you plan to bend. A smaller bend-radius is usually better when you’re bending tubing that needs to fit into tight spaces, like an in-cab rollcage. A centerline bend radius three times the diameter of the material is generally considered the smallest acceptable bend radius for a rotary-draw bender and die set without using a mandrel, but this general rule really depends on the material’s wall thickness. Minimum wall thicknesses are listed on Van Sant’s Model 4 die chart”:http://vansantent.com/model_4_bender_dies.htm.

    bender in action=
    I ordered four die sets so that we could build rollcages using larger diameter tubing where we really needed the strength and use smaller, lighter tubing in less critical areas to save weight. The 1.25” x 4.5” radius is great for bending lightweight, non-structural tubing for things like body supports, dash framework, etc. I’ve built most of our Tacoma’s cagework with the 1.5” x 5.5” radius die set, except where I used the 1.75” x 5.5” die set to bend the perimeter tubing inside the cab. The 2” x 6.5” radius die is perfect for bending open-topped Jeep rollcages and SCORE’s new rulebook mandates that all vehicles weighing more than 4,000lbs must use at least 2” diameter tubing for the primary rollcage. We don’t have any immediate plans to start racing in SCORE specifically, but many off-road sanctioning bodies look to SCORE and tend to follow their rules.

    OK, I know what you’re wondering. Dies are expensive and if I had to choose just one set, it would probably be a 1.75” die with a 5.5” radius. 1.75x.120-wall DOM is strong enough to build safe rollcages and 1.75x.090-wall tubing is actually lighter AND stronger than 1.5x.120-wall tubing, so it’s pretty versatile.

    Accessories

    Van Sant’s tube bender’s survival kit is a great package of useful accessories for anyone that’s just starting to bend tube. I already owned a digital angle level, but I did buy a dial level & base clamp and an inexpensive Angle finder. We’ll talk more about these tools and how they’re used in next month’s article.

    In the meantime, check out this awesome tube bending software from 2020 Software Solutions. I could write an entire article about Bend-Tech Pro, but for now I’ll just say that it’s a great tool and a real time-saver. I’ll be using this software as an integral part of our tube bending articles to help illustrate points related to rollcage design and tube bending/notching techniques, etc.

    Tube Bending Techniques

    Click here to continue reading part two of this article. JD2’s instructions also explain how to set up the dies and start bending. Also make sure to check out these well-written articles about tube bending:

  • Tube Bendin’ 101 by Rob Park on Pirate4×4
  • Fab 101 article about bending tube by Craig Perronne on Off-Road.Com

    This Article was originally published on Off-Road.com May 2006

     

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