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LifeTrac off Track?
  • The LifeTrac I'm lead to believe has some issues with its drive train. It's little suprise really, has anyone seen a tracked vehicle that uses pneumatic wheels for traction?

    Don't get me wrong I can see how the current design originated though the iterations to the design, but I think at this point they really need to decide if the vehical is to have wheels or tracks and design accordingly, this mixture of both is a little misguided.

    If I was building one myself I'd stick to tracks, but manufacture the tracks like any other tracked vehical and more importantly drive the tracks like tracked vehicals, with the use of drive sprockets. I was thinking that you could make sprokets out of  disk brakes, mearly drill and grind holes to make the teeth. The tracks could be made from standard stock steel, angle iron and flat bar, the flat bar for the track itself, two lengths of angle would be welded on perpendicular and sit each side of the disk brake when that track piece reached the sproket. One bolt running through the 2 lengths of angle would serve as a drive pin and also join one track peice to another as it would also pick up the adjoining track section.

    The tracks themselves would be pretty time consuming to make, but the way I see it, traction is kinda important for a machine that's moving dirt around.

    The only real issue I see with the above is that disk breaks are typically pretty small diameter, and given how the chassis of the LifeTrac is currently designed, ground clearance would be a little problematic. I guess you could get larger disks, like something off a SUV or 4wd if ground clearence was an issue.

    Or, just stick with the wheels, but get some decent mudslingers!

  • 19 Comments sorted by
  • All the tractors I've seen use what LOOK like pneumatic tires...just really big ones. Commercial skid-steer loaders seem to use solid tires when they don't use all-rubber tracks.

    Even the big earth-movers use what appear to be air-filled tires.

    A metal-track option makes a lot of sense, especially if you want to use the tractor for really high-torque jobs where you don't care about tearing up the ground. Maybe your idea would work as a modification to the LifeTrack. Remove the hub motors and turn the wheels into idlers. Extend the circumference of the chain-and-rebar track. Install two big hydraulic motors somewhere above the existing wheels. Either turn a disk brake into an appropriately sized sprocket or make one another way. At any rate, use one or more sprockets to mesh with the chain so the hydraulic motors move the track (and the tires just keep it in place). The track would form a triangle as it passed around the two tires and one hydraulically-powered sprocket. 


  • Hi Mat,

    I was a constuction engineer in the Australian army, and have mates in the earth moving business so I've seen my fair share of machines using pneumatic tires and tracks, and both have their place (especially in tactical construction). Yes tractors and earth movers can use pnumatic tires, generally quite
    large (as the machines are large too) and designed for traction. But that wasn't my point, the point is you choose which one is more appropriate and stick to it. Tracked machines don't generally have good ground clearence, pnumatic tired vehicals generally do. You never see pnumatic wheels driving a tracked vehical, rubber tracks yes, but those rubber tracks are still driven by all metal sprockets.

    I also thought that a three sprocket system might be the better option, two load bearing idlers and one driving sprocket which would sit above them. I don't think you can reuse the current chain and rebar track, I've been running over that in my head, and I think it would be difficult to get it to work. For one the chain is currently welded on the end of the rebar, which is bent, so trying to drive the chain would be impossible in its current location. But I don't see that it's a worth while excersie. For one thing manufacturing a sprocket to drive stock chain, I would think, to be reasonably complicated but the real problem I see with the current tracks is there is very little side load stability. Imagine if the LifeTrac had to travel along the side of a hill, what's preventing the wheels from slipping sideways on the tracks? Just the bent rebar? What happens then when the rebar punctures one or more tires? Things could get dangerous very quickly.

    The design of my tracks cators for that side load by the angle iron locking on each side of the idlers, which prevents the idlers (or drive sprocket for that matter) slipping sideways.

  • "You never see pnumatic wheels driving a tracked vehicle..."

    Oh, okay, I see what you mean. I thought of the current metal track more as a set of snowchains than tank treads. I have strong doubts about the chain in between the wheels doing anything at all. The part of the rebar that is in contact with the ground is just going to flex out of the way rather than exert any force. I think the increase in traction is just from the rebar directly under the wheels. So, you could save yourself some time and money by just making the chain long enough to go around each wheel the snow chain it actually is.

    And that brings us to the excellent point that the rebar is only oriented one way, so it's not going to do much to stop the tractor from sliding sideways down a hill.

    Maybe tank treads could be cast in a sand mold with steel from the induction furnace. That would allow you to make the complicated shape with less effort. Can you weld cast metal?

    Or what about this...maybe they could take one of those big earth-mover tires and cut off the side walls, then bolt short pieces of angle iron or channel along the inside at regular intervals. That would act like the rubber tracks that skid steer loaders currently use and the pieces of channel bolted along the inside would keep it on the sprockets.
  • Vote Up0Vote Down
    January 2012
    Well done team for all that you've shared on OSE.
    I'm really supportive of open source, these are constructive comments, to help move the project forward, although they discuss current flaws.
    I'm keen to build a tractor, I like the idea of long term adaptability and maintainability.

    • Current imperial dimension plans & designs are unuseable in most of the world.   Most places use metric, and often only metric steel stock and tooling are available.  Are there thoughts around metric? This will no doubt alter a lot of the force angles, calculations, jigs, templates, kitsets etc.  The materials list makes my head hurt with all those fractions. Your 4" standard is 101.4mm for me, for which the second hand steel dealer will offer me 100mm x 100mm box section. It would seem difficult to turn your plans to metric after you've finished all your research & development.  Remember the mars probe that crashed?

    • There doesn't seem to be many triangles in the grid design of the main frame.  Only the bolts and connections appear to be stopping it twisting in x,y,z axis.  What have you found in testing?

    • Skid steer is just too blunt on the ground for many applications.  It rips up bitumen, scuffs stones, wears rubber on concrete, tears up turf and just generally makes for a very jumpy ride on any hard surface. Most people I know are very happy when the messy & noisy skid steer loader finishes the job and leaves site.  Is the pivot steer design dead? Is steerable front wheels doable? Coarse steering makes subtle movements difficult in lifting applications.

    • I've never seen a skid steer loader with the wheels that far apart, they're always close together, for easier turning. Often you'll rock on to two wheels when changing direction, to make the turn easier and faster. That's not possible with the wheels so far apart.   That means LifeTrac is working more like a scrub steer bulldozer, which is an even clumsier tool than a skid steer loader. Dozers generally need to have a lot of weight to be safe, effective and useful.  This is a long way from the finesse of a wheeled tractor.

    • A bulldozer with a front end loader is a traxcavator. Slow, clumsy, tools requiring powerful engines to be effective, in common use before back hoe excavators.  Now only accepted as useful in specialist applications such as loading & mounding in difficult ground conditions like raw quarry pits and hot steel slag heaps. Search for traxcavator and check the images tab.  Hardly a new or modern one to be seen, they're all retired, in secondary lives or vintage.

    • LifeTrac development seems really focused on improving front lifting application, not much on agricultural 3 point linkage application.  Will this continue to be the focus? Or is this just because you're doing a lot of fabrication at the moment, and will move onto farm work later? Or is it just the selection of video's you've made?

    • Has energy efficiency entered your calculations?  Tracks & skid steering is energy inefficient. Excess tare weight is inefficient. Hydraulics while adaptable are a lot less efficient than direct drive. Motors working hard because they're too small is also inefficient. Energy efficiency is usually a critical design factor, and even more important in poorer parts of the world than America. Efficiency is sometimes traded off for gains in other areas, but is this the case with the LifeTrac? Your design list aims for the tractor to support a 40 acre farm, so that's a lot of tractor working hours, so thats a lot of scarce and expensive fossil fuel, or precious and time consuming to make ethanol.  I can't see how you can fundamentally rework so much of your design for more efficiency, when the whole layout depends on your skid steer and hydraulic function.

    • Tractors have been in development for more than 100 years, and an awful lot of lessons have been learnt, careful thought applied, and alternate designs tested and failed. Millions of man hours and dollars. LifeTrac has lots of good ideas, but doesn't seem to draw on much good knowledge in the tractor or manufacturing fields.  It's like your starting again for no really good reason. A good example is the kinked boom on the lift arms. Dozens of front end loader manufacturers have tried straight, then moved to kinked. It's well known, it works. It's unavoidable physics and angles.

    • For the type of lifting you're doing in a lot of the videos, an overhead boom would seem more appropriate.  Hinge at rear top, hydraulics in middle, hook out the front, no bucket.

    • Some older ideas on overhead booms found on tractor cranes   A lot are still in use in fabrication shops. They're fore-runners of modern telehandlers in some ways.  Many laughs for ugliness, applicable lessons in what not to build.  Form follows function, elegant designs often work especially well.

    • Would a redesign or alternate machine or variant, still using many of your design principles such as simple 4x4 construction, universal power pack, common connectors etc but on a two horizontal-rail more like a tractor design be feasible?  Sometimes more can be learned or achieved from completely throwing away an early design.

    Hopefully contributors can answer some of these issues, and I hope they help. 

  • If one standard has to be chosen, then it should be metric. I would prefer finding a system that is dimension-agnostic.

    A vehicle/furniture/machine construction kit should include crossbracing. Either plate triangles or space-frame characteristics.

    Skid steer is practical on 1) small vehicles or 2) giant vehicles with no room for giant steering systems. With the LifeTrack's current wheelbase, it can be skid steer only as long as it remains light. Load the thing up, however, and skid steer won't work.

    As best I can tell, FeF doesn't have any fields yet, let alone oa farm. So there's no need for the tractor to actually do any agricultural work. The money seems to be going towards the fabrication tools.

    I interpret the LifeTrack as a proof of concept. The current design is a dead end, but it illustrates a point.

    Bootstrapping has a discussion of parallel-rail frames. Personally I think they're a better idea than the current 3-way square tube construction technique.

    At the moment, my concept is a single unifying modular system for all the vehicles and most of the machines. For example, start with a rectangular frame of whatever size is appropriate (try to standardize frame dimensions). Then bolt on one of a family of suspension/propulsion units (double wishbone, tank treads, etc). Then drop a mission-specific cab and or tool on top of the frame (vehicle body, loader arm, etc).

    I think we'll get closer to a system like that as we more clearly define the requirements for all the different missions it needs to function in.


  • @DaveMC - All your points are completely valid and quite obvious when you start looking at the current design of the LifeTrac III at any depth as you have Dave.

    I've already started a separate skid steer tractor ( that will be completely redesigned and engineered from the ground up, while not reinventing the wheel so to speak on a lot of the basic things. The design time will be slower but I think the end result will be a much more functional tool and one that does what it is made for well, namely being a skid steer (optimizing wheel base, loader arms, safety, etc..) And as a Canadian, it's naturally it's going to be in metric ;)

    I love the versatility of the skid steer but indeed it is not really of much use in the agricultural world for plowing and not destroying the ground due to how hard it is on the ground. There have already been some discussions with the OSE Europe guys this past week about starting a steerable tractor design. Their plan was to hopefully find some old plans for a tried and true tractor and then reverse-engineer/simplify/improve the design and open source it which I think is a great idea. I was actually going to be creating the wiki framework this weekend after I finished editing some of the old LifeTrac pages. 

    With the redesign of the wiki I'm trying out, you should be able to get to any sort of tractor (skid steer, articulated steering, conventional steering)  from the main LifeTrac page under the product evolution section.
    It's a fresh layout and one that I'm actively working on right now so bear with me as the pages keep shifting around haha...

    Anyway, it would be great to get any additional input you may have as the projects continue!

    @Matt - Yes the initial design of the LifeTrac III is around 4000lbs with the two 500lb powercubes on them. With LifeTrac IV I gave him a design to retrofit III to bent the loader arms. He then and added about 1500lbs of additional ballast to the rear of the vehicle in order to lift a pallet of bricks that weighs 3000lbs. It's able to just do this I believe last I heard. But...operating load should not be equal to tipping load for natural safety reasons. Additionally no engineering has been done on the frame, mounts or wheel shafts so it's nothing but unknowns for if what is currently in use can sustain these kind of loads for any extended use. Maybe some of that will get done at some point...

    I do like your standardized method, the problem is that each vehicle has such different requirements and the complexity differences between something like tank treads or having an wishbone suspension are pretty huge when you start getting into the details. But again only obstacles and if we could make it all work on a standardized system that would be awesome!
  • mrsquish was talking about electric tractors and it inspired a thought. The latest videos from FeF show them having to add 1000 pounds of weight to the back of the tractor so it can carry a big pallet of bricks. Well, based on what people are saying about electric tractors, why not convert the LifeTrac to electric drive? Electric motors would be direct replacements for hydraulic motors (maybe a little bigger) and 1000 pounds of batteries would give it all the torque and/or running time a farm could possibly use. It won't work as well during the winter, tho.

    I can't find it now, but I remember analyzing the size/weight of nickel iron batteries and calculating that a power-cube sized battery bank would weight right about 1000 pounds.

  • Hey Matt, sure that's a great idea. It's quite a bit more complicated than that and you need to get into some heavy electronics. If anyone wants to start down that road they're more than welcome to! Personally I'm going to be focusing more on just the mechanics of design and making it work with the powercube for right now and sure once the electrical system has been figured out I"m sure there will be enough real estate to convert it to electric!

    Looking into electric forklifts is a good place to start!
  • This.

    This design should have won. This is how the "universal rotor" should work. The current design makes zero sense, particularly now that exotic couplers are being added to it. The quick connect assembly now as at least two, maybe three, couplers between the motor and the wheel. It's going to be harder to machine sprockets and double chain then to durn an axle on a lathe. All this does is make the component even larger and even harder to mount. It needs to get smaller, not bigger.

    That assembly Flaviano modeled is exactly how all existing construction equipment connects the wheels and motors (when it isn't a single solid axle). It is the best possible compromise between all the different requirements.

  • Yep, that's the one I was going to use on the LifeCat and was going to be contacting the creator next week actually!

    Glad to see you're on the same page hahah throw that comment up on the "community feedback" page as well for the LifeTrac IV!
  • LOL, already working on that :)
  • Vote Up0Vote Down February 2012
    Hey Mat, glad to see someone is reading the crap I write!

    Regarding EV Tractor, after building my brick machine, I'll be seriously looking into this. If not a tractor, at least a loader of some description. The main problem with all electrics (as I eluded to in the CEB thread) is the linear actuators. Electric linear actuators of sufficient size for a tractor are difficult if not impossible to find, and if you do find them they are very expensive compared to hydraulic.

    Probably the easiest EV Tractor would involve an electric drive line and electric hydraulic pump.

  • That's a good point...I was only thinking about the drive train. Hydraulics has better power density than electric linear actuators. Also, the cylinders are probably simpler to engineer than electric linear actuators of the same capacity.
  • Vote Up0Vote Down
    March 2012
    Redesigning LifeTrac?  Check this out: it began.

    I want a Lifetrac and have been following its development ever since I became a True Fan (about # 120) but my initial euphoria upon discovering LifeTrac has been pretty much wiped out by the extended number of versions and design problems, not to mention the critiques at this site by others here who have relevant expertise.  I thought :"  Bobcat did not just drop suddenly from the sky; it has probably been through a number of design iterations", so I searched bobcat history and found the excellent doc referenced above, complete with photos, dates, design changes etc.     It is an interesting read and there are some good insights that a LIfetrac designer ought to know about.  

  • Don't make the mistake of comparing the GVCS tractor to other tractors. The GVCS is a system of systems, which means each component (IE machine) is evaluated based on how it contributes to the performance of the entire GVCS. Inefficiency at the tractor can easily be offset by increased efficiency from integration with the other machines. Just because something looks like a mistake doesn't mean it is. It could just be a compromise with something that is not immediately visible because it's not directly part of the tractor.
  • Vote Up0Vote Down
    March 2012
    @ Matt_Maier :  Good point to assess Lifetrac in context of GVCS.  You said, however, in an earlier comment that the current LIfetrac design is a dead end. I thought that meant Lifetrac is just a poor design regardless of whether it is being compared to Bobcat.  I'm sad if that's true.  
     I  DO compare Lifetrac with Bobcat because Lifetrac is starting to look like Bobcat and seems to be asked to do Bobcat jobs.  In fact, my own interest in the tractor at this time is mostly as a digger and loader for use with a CEB press. If Lifetrac design is dead, maybe Bobcat history can provide lessons,ideas or an actual model to work from. I wonder if a more tractor-like hybrid could be successful as follows:   Use a more elongated frame with four-wheel hydraulic drive--all wheels same size.  Wheels on the cab end are powered but not steerable; wheels on the other end are both powered and steerable; power cubes sit along the part of the frame not occupied by the cab; bucket is located on the cab end for good visibility in loader mode (operator facing bucket).   Loader arm pivot points and immovable  end of hydraulic cylinder are located at end opposite of the bucket.  To convert from loader to tractor configuration, replace the bucket with a three-point tractor hitch and swap the locations of the driver's seat and the control levers: do this by rotating them 180 degrees around a common center point (by taking advantage of some sort of swivel plate or the flexibility of long runs of the hydraulic hoses,or by having two hydraulic bases and moving the valves from one side to the other. )

    The points of the Bobcat history are (1)  (2) For those of you who are working on redesigning Lifetrac as a skid steer, a study of the various precursors of today's Bobcat might turn up some useful design features or even a good starting point for a redesigned Lifetrac. 


  • Vote Up0Vote Down
    March 2012
    oops: please disregard the last 3 lines. I thought I had deleted them.
  • "You said, however, in an earlier comment that the current LIfetrac design is a dead end."

    > I meant the way the frame is built. Bolting together tubes is great for prototyping; not so great as a permanent design choice. No one ever needed to demonstrate a tractor frame. It was the performance of simple/cheap motors, bearings and the power cube that needed to be demonstrated. As the design is refined it will most likely go through at least one major redesign of the basic structure, abandoning the bolted-together-tubes approach.

    > I agree that the "tractor" is really a Bobcat. Most likely a design iteration will include increased modularity so it can be changed from a Bobcat type layout to a tractor type layout. Skid steering was merely an easy first approach.

  • Vote Up0Vote Down
    March 2012
    @Matt:  I like the idea of a layout that can changed between tractor and loader.

    How long do you think it will be before the frame re-design? It seems like the power cube is pretty well finished and I have not seen any problems posted about the hydraulic motors, but I have not seen any results lately on the new wheel mounting system or on the fix related to the hydraulic cylinders. 

    I have a bunch of salvaged 4-inch structural steel C-channel that I got free for the hauling.  I have been wondering whether, in spite of the obvious problems with its shape, it could be used it to weld/bolt together such a frame for a slightly smaller skid steer/tractor that has a bucket about 3.5-4 feet wide.  

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