Extreme Traction: Open Source Wheel Tracks

After the initial test drive two weeks ago – we have built and tested wheel tracks for LifeTrac Prototype II, the hydrauilically-driven, open source tractor. Now LifeTrac is able to handle extremely rough terrain – which would otherwise halt other wheeled vehicles, including LifeTrac I. LifeTrac II can go over sizable humps and holes in the ground, and riding LifeTrac II is a spectacular experience. Here we show the build, installation, and testing of the tracks on rough terrain:

Extreme Traction from Marcin Jakubowski on Vimeo.

The addition of tracks makes LifeTrac well-suited for navigating through many of the erosion ditches and rough terrain of Factor e Farm. This is a great relief on practical grounds, as we are now well under way to gaining control over our landscape. Also, there is clear indication that the full traction is a lead into building bulldozers for earthworks.

The wheel tracks are robust, quite satisfactory, and well-worth replicating. They cost $520 in off-shelf parts for both tracks, totaling slightly under 70 feet of chain. Our particular design is designed for 16” truck tires. The test drive proved that the tracks provide the required traction, don’t slip on the wheels, and stay centered on the wheels.

The treads consist of 3/8” chain and 1” rebar, bent with our shop press on a bending jig (download in dxf format):

The rebar pieces are 20” long, and they are welded to the chain every 5th link. Each track has 40 treads, and totals 160 links of chain. These exact numbers happen to work for the exact LifeTrac II design as shown in this Blender design drawing. Note also that there are different types of 3/8” chain – and the type with exactly 9 links per foot is the one we used. This particular chain, in allows enough space between links for the rebar to fit flat on one link for welding (without hitting adjacent links). Chain with smaller links will not allow the rebar to touch only a single link, thereby complicating the welding. Moreover, we welded the chain on the inner side of the rebar – to minimize wear on the tires – by allowing the wheel sides to contact the smooth chain instead of the more rough rebar.

The bending jig works well with an 8.5” wide press foot consisting of a (1”x4”x8.5” steel slab). The rebar bends into shape readily with 20 tons of force. There were defects in 2 of the bent pieces – as the rebar began to crack at the bend. We fixed this by welding, and reducing the speed on the press cylinder by throttling down LifeTrac I, which powered the press.

It took about 30 minutes to cut the rebar for 1 track with an abrasive metal cutoff saw. It took 30 minutes to bend them, and 3 hours to weld. Thus, making one full pair of tracks as above takes one full day. It took another full day to figure everything out – from design, to the build of the rebar bending jig, to streamlining the workflow. Torching the rebar to pieces also works, but it then requires grinding prior to welding.

Overall, tracks are an excellent concept – which we tested first-hand with delight for ourselves, and we recommend them highly. It was plain fun to negotiate the big bump that you saw in the video, like on a roller coaster ride. Moreover, since the contact with the ground is maximized, the operator is in for a very smooth ride as perturbations on the ground do not transfer to the operator. We know that anyone who understands what it means to get stuck in mud or holes or ice will appreciate the access to low-cost tracks, and we are glad to document a working design.he ini

19 Comments

  1. Aigars Br?velis

    Space Vikings: Danish Duo Preps for Suborbital Flight
    Updated: 2 days 10 hours ago
    Print Text Size
    Tony Deconinck

    Tony Deconinck Contributor
    AOL News
    (Sept. 3) — In 24 hours, Kristian von Bengtson and Peter Madsen will know victorious elation or anguished, crushing defeat.

    The two are vying to get one step closer to becoming the fourth group in history to put humans into suborbital flight — the other three groups have been the space programs of the United States, Russia and China.

    While the pair hopes that their launch window stays open, their countdown will be filled with the kind of high-stakes anxiety unknown to people outside of national space programs. Every minute until the last will be filled with furious tinkering, checking and rechecking systems under a dark specter of self-doubt.
    The Danish built amateur rocket Tycho Brahe leaves Copenhagen Harbor towards the island of Bornholm in the Baltic Sea on August 31, 2010 for a test launch, escorted by a submarine also built by Copenhagen Suborbital.
    Jens Norgaard Larsen, Scanpix / AFP / Getty Images
    The amateur rocket built by Danish group Copenhagen Suborbitals leaves Copenhagen Harbor on Tuesday for the island of Bornholm in the Baltic Sea for a test launch.

    Right now, the team’s engineers and designers are methodically thinking through each element of the design and execution of their homemade suborbital rocket, the Hybrid Exo Atmospheric Transporter — dubbed HEAT-1X.

    Now completed and ready for launch, the HEAT-1X was the brainchild of Madsen and former NASA architect von Bengtson. They are the founders of the Danish nonprofit company Copenhagen Suborbitals, which aims to safely launch a human being into space in microsized craft.

    A few days ago, the team moved the rocket to Bornholm, a small island in the Baltic Sea. Situated 20 miles from the nearest landmass, it was a strategic foothold that once boasted the largest medieval fortress in Northern Europe, and for the same reason is now an ideal location to test spacecraft.

    As its payload, the rocket will carry the Tycho Brahe-1, a micro-spacecraft carrying a test dummy entertainingly included with other “part-time specialists” on the project’s team page.
    The Danish built amateur rocket Tycho Brahe leaves Copenhagen Harbour towards the Island of Bornholm in the Baltic Sea on August 31, 2010 for a test launch, escorted by a submarine also built by Copenhagen Suborbital.
    Jens Norgaard Larsen, Scanpix / AFP / Getty Images
    If this weekend’s launch is successful, Copenhagen Suborbitals will move one step closer to becoming the fourth group to put a person in space. The other three groups have been the space programs of the United States, Russia and China.

    A Plexiglas dome will grace the top of the rocket, giving the test dummy — and perhaps one day an astronaut — a 360-degree view of the heavens. While any future astronaut will have the ability to make some limited adjustments and maneuvers, all of the important actions will be performed by the mission control team on the ground.

    The interior of the one-man craft might not be fit for the claustrophobic; the entire rocket is slightly more than 25 inches in diameter. By comparison, a typical airline seat in the economy section is roughly 18 inches across.

    The HEAT-1X is the team’s most advanced rocket, and the first at full size and carrying a payload.

    Back in May, von Bengtson and Madsen successfully tested a static booster powered by liquid oxygen oxidizer and polyurethane fuel. That booster will burn for 60 seconds, providing enough thrust to achieve their 19-mile voyage without exceeding 3Gs, which would be comparable to the G-force experienced by space shuttle astronauts during liftoff and re-entry.
    Peter Madsen (left) and Kristian von Bengtson next to the spacraft Tycho Brahe.
    Erik Sellgren
    These guys are aiming for the stars. Peter Madsen, left, and Kristian von Bengtson — the founders of the nonprofit company Copenhagen Suborbitals — pose next to their spacecraft.

    The only thing more remarkable than the program itself is how much the company has been able to achieve considering its limited budget. Copenhagen Suborbitals is a nonprofit that has been funded almost entirely by sponsors and supported with the help of volunteers.

    Madsen and von Bengtson say they’ve been able to achieve this dream on a shockingly meager budget of 50,000 euros (approximately $64,000). Compare that with China’s Shenzhou space program, which was reportedly accomplished on a “shoestring budget” of only $2.3 billion — itself a fraction of NASA’s annual budget of $18.7 billion.

    If this weekend’s anticipated launch is successful, the team plans to build three more rockets, testing and tweaking each with an eye toward putting a human into suborbital flight, and eventually into space.
    Spacecraft Tycho Brahe with crash test dummy designed by Kristian von Bengtson.
    Thomas Pedersen
    This crash test dummy is going to get an amazing view. This weekend’s planned launch will be the first Copenhagen Suborbital launch featuring a dummy.

    While the program is buried in physics, engineering and innumerable calculations, beneath it all there is still a mystical element that burns at its center.

    When asked about a comment in which von Bengtson called the craft an “elaborate art project,” Madsen — a successful mad tinkerer and submarine builder — told the New Scientist he hoped their work would inspire others.

    “Hopefully this mission will give everybody watching an experience of joy, through realizing such things are possible,” he said. “You can go home and build your own personal spacecraft.”

    If they’re successful, they may achieve something that mankind has longed for as long as we’ve looked at the skies at night.

    The ability to touch the stars.

    Filed under: World, Weird News, Science, Tech
    Tagged: bornholm, kristian von bengtson, outer sp

  2. Adam Mitchell

    Awesome!

  3. Abe

    AWESOME!

    To make a bulldozer from this, all you need is a blade on your loader.

    1. Marcin

      …And more torque on the wheels. Right now, each wheel produces only 300 lbs of driving force, or a total drawbar pull/push of 1200 lb, assuming perfect traction, which we now achieved. Serious earth moving would begin with about 3 times this force. We could achieve this either by using different wheel motors (doable, as wheel motors are quick-connected) or by using gear reduction via gears or heavy duty chain sprockets.

  4. Abe

    One question:

    With the tracks on now, do you need 4 wheel drive, or can you go to 2 wheel drive? It seems to me that with the tracks on there, there is no need for the 4 wheel drive.

  5. Abe

    oh right, so you need more torque, that is interesting. And that also adds a level of complexity.

    If you can get away with just 2 wheel drive with the tracks, it might be better to do the gear reduction for just 2 wheels.

    If you have to stick with 4 wheel, different wheel motors might be better.

    But, you would also think you could do a bit of earth moving with what you have. I mean, 1200 lbs drawbar isn’t too bad for 18hp, right?

    1. Marcin

      The question boils down to speed. If one has all unlimited time, one can move mountains with 1200. For general contracting work for hire, that would be likely to make one go out of business.

  6. Abe

    I love the new development on LifeTrac, the DIY track chains. That was awesome! I really want one, now!

    A few questions, cause you guys are way ahead of me on this:

    You said on the blog that you need more torque for serious dirtwork. Do you have a wheel motor replacement in mind that might work? I’m not sure what sort of torque I need to do the dirtwork projects I have, but anything would be better than what I have now.

    Can you get away with just 2 wheel drive with the tracks, or do you have to stick with 4 wheel drive? The reason I ask is that most of the track machines I see only have one drive mechanism, whereas you would have 2 for each track (2 wheels = 2 drive mechanisms). Is this necessary? I would assume that you could just go to 2 wheel drive, and let one wheel free spin, cause you have all the traction you need. Of course, 2 wheel drive ignores the issue with wheel torque, but if you had a wheel motor with a lot more torque, could you just go with 2 instead of 4?

    I’ve seen micro dozers that are quite small (15 hp, garden tractor size), but I have no idea about their torque. I also don’t know what I would need around here, though I am sure bigger is better.

    I am thinking of replicating your work on a smaller scale design, maybe using a 3 ft cube as the building block, instead of your 4 ft cube. This would primarily be a bulldozer design for my place here. It would be nice to have a PTO and hydraulic take off to power some accessories, like a chipper, maybe wood splitter, mower, etc. But, I really need something I can dig ponds and maintain my road with. And on my hill, I need tracks, wheels are no good.

    Do you think I could get away with 3″ square tubing? I think I may actually look for scrap metal instead, probably sourcing car frames and such, basically to save cost.

    Could we set up a discussion on your forum or somewhere to talk about replicating the LifeTrac design?

    Is there an updated parts list somewhere with part numbers from Surplus Center?

    Do you know of anyone else that has made one?

    I think you also need better documentation of the build, especially of the finer details. Maybe, with my replication, I can document everything, and do a how-to type document to contribute to the project.

    Any suggestions or details would be great. I’ve downloaded the blender docs, as well as all of the related videos and blog posts.

    1. Marcin

      We’re using these motors:

      https://www.surpluscenter.com/item.asp?item=9-7469&catname=hydraulic

      These have twice the torque: https://www.surpluscenter.com/item.asp?catname=hydraulic&qty=1&item=9-7735

      At 9700 in-lb, that means 646 pounds of force per each wheel at the 15″ wheel radius.

      Just think about it rationally. How much force does it take to move dirt? You can’t move much with 1000 lb of push. At 5000 lb, you’re starting to be in serious business.

      The Northern Tool bulldozer weighs 5000 lb if I’m not mistaken. That means a max push of about the same amount.

      No problem. Use our existing motors, gear-reduce 5-fold, and you have 7000 lbs of force. You’ll be going 5 times as slow, but, LifeTrac II can be retrofitted readily.

      Solution is around the corner.
      Can you get away with just 2 wheel drive with the tracks, or do you have to stick with 4 wheel drive?

      We haven’t tested that for slippage. I imagine it will work, but at super heavy duty work, you’ll probably slip inside the chain, unless your chains are extremely tight.
       
       The reason I ask is that most of the track machines I see only have one drive mechanism, whereas you would have 2 for each track (2 wheels = 2 drive mechanisms).  Is this necessary?

      If you’re using rubber wheels, I think so. Other drives are steel cogs, which don’t slip.
       
       I would assume that you could just go to 2 wheel drive, and let one wheel free spin, cause you have all the traction you need.  Of course, 2 wheel drive ignores the issue with wheel torque, but if you had a wheel motor with a lot more torque, could you just go with 2 instead of 4?

      Sure.

      I’ve seen micro dozers that are quite small (15 hp, garden tractor size), but I have no idea about their torque. I also don’t know what I would need around here, though I am sure bigger is better.

      We plan on appropriate scale of about 200 hp for heavy duty work, with steam engine drive. This is as far as one needs for easy advanced civilization.

      I am thinking of replicating your work on a smaller scale design, maybe using a 3 ft cube as the building block, instead of your 4 ft cube.

      This callout has already been made here.
       This would primarily be a bulldozer design for my place here. It would be nice to have a PTO and hydraulic take off to power some accessories, like a chipper, maybe wood splitter, mower, etc.  But, I really need something I can dig ponds and maintain my road with.  And on my hill, I need tracks, wheels are no good.

      Do you think I could get away with 3″ square tubing?  I think I may actually look for scrap metal instead, probably sourcing car frames and such, basically to save cost.

      Yes, you can save the $1k in cost for the frame at the expense of labor.

      A small frame, if half the size, would be $500 in virgin steel.
       
      Could we set up a discussion on your forum or somewhere to talk about replicating the LifeTrac design?

      There is one here  but we are reworking our net  presence – so wait a couple of weeks. In the meantime, can you repost this message as a blog comment?

      Is there an updated parts list somewhere with aprt numbers from Surplus Center?

      The complete list is here.  Power Cube is here.

      Do you know of anyone else that has made one?

      No. Thad of Broken Sidewalk Farm is talking with us about building one.
       
      I think you also need better documentation of the build, especially of the finer details.  Maybe, with my replication, I can document everything, and do a how-to type document to contribute to the project.

      Sure. We need more  technical documentors here.

      Any suggestions or details would be great.

      The suggestions are to understand the concept, design rationale, specifications, and basic back-of-envelope structural calculations prior to building. Also, you can use 1/4” steel for the loader arms. We’re using 3/8” for extra heavy duty.

      Marcin

  7. antimonio

    AWESOME!!!

    Guys, I think you should create a Flattr account so you get micropayments each time you do some good progress on some project and blog about it. You may get much less than with TrueFans, but anything can help!

  8. Will Freeman

    Hi there, love your work. I have a concern and I’m not sure this is the proper place to raise it but I couldn’t find a good place in the forums. It is this: From a soil heath perspective, is there any significant downside to using a track design? I see a lot of soil disturbance happening in that video, though I can’t tell exactly what happening on the ground.

    Compaction should be reduced, even the hard rebar treads should distribute the weight better than conventional ag tires. On the other hand in clay soils the treads sliding sideways through the soil could cause “slicking” which hampers root growth and water movement through the soil. Repeated use could cause significant damage, especially at the edges of a field where turning maneuvers are frequent. Has this been addressed?

    Thank you for your work, I am excited to get involved as soon as I have the time. My passion is biochar and agriculture and that will be the focus of my efforts, I look forward to contributing.

    -Will

  9. Will Freeman

    One more note: from the perspective of pulling an implement behind the tractor one of the most important demonstrations would be a smoothly radiused 180* turn. I assume that should be possible but it should be attempted none the less.

  10. Joel

    If you wanted to go with steel cogs, might it be worthwhile to have small cogs on the drive wheels? That would give you more force for a given torque.

    It might even make sense to add a small cog that catches the existing track with its own independent motor, which adds drive force at low speed, but idles at high speed.

  11. Miquel

    I agree with Will:

    When you explained the design of Prototype II months ago, that was actually the first thing I thought about: soil destruction. With normal big industrial tractors, soil compactification over time really is an issue. That would be minimized with tracks, but the soil surface would be teared apart instead. That is not good.

    Agriculture, specially permaculture is difficult to get right in a closed cycle over long periods of time. You have to think about it like you do about engineering life-time prototypes. Soil
    degradation is nearly the most important problem to solve. The reason is that sometimes the erosion is only very gradual, and not seen over
    few years. So I am concerned that a tractor with tracks could not be suited to life-time agriculture.

    Actually, very few civilizations have avoided soil degradation, and the few which have retained soil productivity over the centuries, were all situated on flood-able river basins (Egypt’s Nile, China, India big rivers…). That has been the only fool-proof way for a civilization to have “eternal” agriculture, and only because the rivers refilled the soil with new materials and nutrients, so in a way that is
    cheating.

    1. Marcin

      Humans have historically moved in to lush forests and they left deserts behind them. An eye-opener on this topic for me was The Green History of the Worlds.

      We do not intent to continue this trend.

      LifeTrac II tracks are designed particularly for construction duties. They may be taken off for 4 wheel drive, where traction issues can be addressed with minor changes, which will be implemented in Prototype III.

      Over time, we aim to remove the need for tractor use, outside of grain crops – after berms and ponds are dug, after permaculture landscapes are created, and after animals are integrated into the ecosystem.

  12. Miquel

    Great reply!

    You read “The Green History of the World”. That is all I need to know.

  13. […] September 14, we finished the loader arms for LifeTrac II – completing the second prototype of the open source […]

  14. Gus

    What pump are you using to drive the hydraulic motors?

  15. […] Extreme Traction post from development stages of tracks. […]

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