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Microtrac Design
  • Hello, I am working on designing a prototype of the microtrac. I have basic knowledge of Sketchup but am planning to use this tool in a small farming operation. I hope to be working as an apprentice at FeF this summer and want to build a working prototype of Microtrac by the time I leave in fall.

    I am currently researching the inner workings of the power cube and how to best incorporate its' advantage of hydraulic power while accounting for the weight of 400 lbs. The BCS walk behind tractor is only 250 lbs, and my farmer friend who uses it says it is hard to maneuver.

    I would like to hear from anyone who has used the first prototype of the microtrac and/or anyone's thoughts on improvement.

    How can we improve maneuverability, keep compactness, design for tight spots and sloped, treacherous ground?

    Will new implements need to be created to fit a smaller quick attach plate?

    I hear that the Microtrac prototype was hard to steady with the one wheeled design. I am thinking two small wheels, like the BCS walk behind tractor would be sufficient.
  • 18 Comments sorted by
  • from what ive seen the powercube is pretty dam big, bulky and not designed to be totally versatile but in theory it can be made smaller.

    however if one can get long enough hydraulic lines you can put the powercube next to your plot and just run the line across.
    i like the one wheel design, even better if you run with one powered wheel in the center, perfect balance and then running 2 smaller wheels like a childs bike with training wheels.
    if you deisgn to use a powered wheel design, especcially with 2 wheels, run a differential with the motor running though that, to turn tightly brake one wheel and you have whats commonly called a cutting brake.

  • thanks for your insight, spike..

    I have no experience with mechanics, cars, engines, etc. Just designing according to mine and others' desire for ease, compactness, and robust design, as seen with the Toro Dingo Utility Loader, it has everything from backhoes, chippers, tillers, mowers, trenchers, etc. The BCS only has options for rotary plow, tiller, chipper, mower. It runs a gas engine, whereas the Toro has hyrdaulic cylinders for real earth moving capacity. Let's try to incorporate quick attach plate for front end loaders and backhoes while retaining ability of steering. I like your idea of the cutting brake.

    Will you elaborate on 'differential'?

    The one wheeled Microtrac prototype seen here has three stabilizing swivel wheels underneath the power cube.

    I really like what I've seen from Toro Dingo Utility Loader, and I think we could get more bang for our buck than the BCS if we made a compact two or four wheeled tractor with a riding option in back.
  • i build race cars for part of my living so may glaze over some things

    ok so somthing like a dingo would allow for a smaller version of the life track, or in other words a smaller version of the powercubes on wheels.
    a small petrol motor, probably of a lawn mower, running a small hydro pump (power steering pump?)
    tracked wheels based on somthing like a mini, 10 inch or smaller.
    allowing power take offs from all points

    a differential is the part of a cars drive line that allows one wheel to drive fast than the other around corners. In a rear wheel drive car the unit is at the back, has an imput from the front (or top in my idea for the microtrack) and two outputs that can go at different speeds depending on traction.
  • It might be worth designing a smaller power cube for the microtrac. We'll probably need a range of sizes anyway and the size/weight of the current design is prohibitive in this small application. 
  • defiantly, somthing along the lines of a lawnmower motor (diesel) hooked to a automotive power steering pump. Very small setup, also the incorporation of lowering the weight of it. i will have a look at it and put some of my motorsport towards it
  • Haha I understand why you might assume I know these terms, but I will keep asking. Thanks for clarifying. Ive been googling many of these terms youre mentioning, Spike. It's quite the learning curve getting into all this.

    the weight of Power Cube may not be an issue after looking at the specs for the BCS versus the Dingo. BCS= 250 lbs, most Dingo loaders= 2500+ lbs..

    Is the Microtrac the only small application that uses a Powercube? If so, I think we could use the current design, retainingthe tractors' relative small size and maneuverability. Im concerned because we need to put our energy into new designs only where necessary.

    Do you think the current open source "chain/rebar" tracks would be sufficient for this design?

    There are far more applications and versatility with the Dingo versus BCS. Only thing is size difference.

    the BCS is a true walk behind and is only powered by a small gas engine, so the user takes the brunt of directing the machine. My friend tells me using the BCS is the hardest work on the farm (although much easier than when he tilled with a fork!).

    Dingo has hydraulic loader arms like Lifetrac and wheels with hydraulic motors. I think we could make it self propelled enough to be easily maneuverable if we put at least one powered wheel per side.

    The PowerCube may also help balance the weight of heavy front end loads.
    My initial idea was a walk behind design where the user was the primary controller, as with BCS, hence why I was concerned about the weight of PowerCube.. Let me know what you think about Dingo vs BCS

    Been tinkering with my drawings. Found that the quick connect wheel plates make a 20 inch wheel have 5-6" ground clearance. Is this sufficient for moving over treacherous terrain?
  • with a dingo you would probably get away with the large power cube, but i still think the walk behind is an idea and such a smaller version of a power cube is required.

    at the moment i think the microtrack is the smallest self propelled requirement, but i feel many more could be devised.

    i think the chain and rebar tracks would work, however if this doesnt a modification that probably would be work doing is the replacement of the rebar with steel.

    i think both of them are nessecary but it depends on usage, if your going to use it like a smaller lifetrack around your farm, house business then go with the dingo design. if you only wish to rototill the ground in your garden a BCS would be best
    It all depend on your usage and care, my paddock is full of large rocks in places and 6 inches would not be enough, in my garden and the front paddock would be fine however.
  • Hello Graham,

    some remarks about Your post concerning weight of a walk-behind tractor.

    As a boy of 14-15 years old, I did some field work with a Holder E12.

    It worked well in plowing and other tillage operations. Its weight without implement in more than 400 lbs, and I think that mass is necessary. While plowing it had a slow steady pace along the furrow. Every two-wheel tractor I have ever seen with much less weight worked poor in tillage getting stuck with every stone or hardpan in the soil.
    So my experience tells me not to go for a real lightweight, it won't do the work. Also I don't think it was hard work, the Holder was easy to operate if You knew how to. It was just fun for me as a boy! Its prob important that weight distribution and steering/brakes are well designed.

    Another issue with the microtractor design is, a power cube with 27+ hp is inapt for a walking tractor. With its low speed (walking) 10-12 hp are more than enough, anything else is wasted.

    I wonder also if designing a two-wheel tractor is worth the effort? The GVCS is a set intended for serious production. A tractor for your home garden doesn't qualify for the GVCS IMO.
    Wouldn't it be better to design a for-wheel tractor similar to this?

    A full-time farmer whose farm is too small for this size of tractor won't be viable in the future. And 4-wheeltractors are much more versatile and easier to operate.

    I would urge everyone to rethink building a single-axle-tractor !!!



  • Well, a single-axle tractor can relatively easily become a two-axle tractor by the expedient of adding another axle! That's pretty much how Holder (and elsewhere, Pasquali, Ferrari, Goldoni, Aebi etc.) ended up making small articulated equal-wheeled 4x4 tractors. And you can put a driven trailer off the tractor pto with a UJ and a simple articulation/oscillation joint, and you've got a load carrier. So there's potentially quite a lot of flexibility if the design is thoughtful enough.

    Personally I think the wheeled articulated LifeTrac 1 configuration was much more promising than the skidsteer-with-bandtracks that replaced it, tracks are good in a number of ways but as the basis for a general purpose farm tractor they pretty much suck.  
  • Personally I think the wheeled articulated LifeTrac 1 configuration was much more promising than the skidsteer-with-bandtracks that replaced it, tracks are good in a number of ways but as the basis for a general purpose farm tractor they pretty much suck.

    Agreed !!!
    Decision for skidsteering was deadly for development of an agricultural tractor. Just a stupid decision, though the reason for this decision is obvious: FeF was unable to build a non-breaking articulated joint.
    Tracks have their qualities, but not if designed as in Liftrac3. Best feature of tracks is their low ground pressure, giving high mobility in very soft terrain. But for low pressure the tracks have to be supported over the entire length.

    Besides that IMO that a second axle should be added to the microtrac, powered or unpowered. It has oo many advantages that outweigh the additional cost.


  • There is another discussion about modular drive systems in a Google group on Microtrac development!forum/microtractor-development

    Thanks for keeping the discussion going here!
  • You wanna make the machines so you got walk in the trench. so the plow or what you have just are there. To make a tractor who work in away that you have in mind not to contribute more soil compaction. That´s also comes to who you farm but i think that can be a important consideration.
  • Hello again,

    Marcin and I just met with Dorkmo on Google Hangout to review progress from our latest design sprint (term used in Scrum to describe a "timeboxed iteration"). During this sprint, I was introduced to a procedure known as contract-first design:

    "By knowing what information those modules need to share with each other,
    Wikispeed is able to build anything that meets the contract that talks
    between modules. Anything that meets that contract is acceptable,
    whether it is made out of carbon fiber, steel, aluminum or even bamboo.
    It’s completely flexible. As a result, teams are able to iterate
    independently and innovate rapidly. That creates the loose coupling of
    modularity. One module can be changed without changing any of the
    others. Anything that meets the contract is acceptable."

    So we are going to try adopting this technique. After our latest design sprint, we realized that there were many great ideas and concept designs being contributed, but no way to make each component's design fit together and communicate. So our next design iteration will be a one week sprint devoted to writing contracts for each interface (where components meet each other; i.e. How will the power cube attach and interface with the frame?)

    You all are invited to contribute interface specifications, which will be reviewed by the stakeholders in the Microtrac project at the end of the sprint.
  • A sprint that's a week long?

    I suggest finding a better way to communicate than a spreadsheet. Most of the stuff you'll want to define will need to be drawn.

    Also, it would be a good idea, before you ask for people to submit specifications, to point contributors to where the mission of the microtrac has been defined. Otherwise people will specify things that work towards different missions.
  • I think this is a good system that can work well. I'm not sure if it is going to be as easy as just defining contracts between modular parts in words. I think a design proposal system among the team to define the contracts first would be needed, however I can see the contracts having to change to deal with conflicts with the module components themselves later on. Also, there could be a choice between methods of contracts that cannot be decided until later in the design phase, for example whether to use a chain and sprocket drive system or a direct shaft drive would depend on space and clearance issues that can only come into play later when the whole design is coming together.
  • Matt, I am open to researching new tools for remote development. Vann, who just left FeF developed a project page for GVCS and FeF projects that directs contributors to all relevant pages. It is about to be launched and we will try it out.

    Id like to hear some feedback, it seems like it might address some of the accessibility problems for contributors.

  • This a is great method of getting new ideas. And now that you'll are using the the agile model and the iteration makes it all the more better to execute.
  • i believe that there is a need for a mule replacement. high torque,narrow footprint. it would be good for pulling logs from remote groves with smaller impact. i have been thinking of a single drive wheel  platform similar to a zero radious mower. the drive wheel will steer. stability would come from two outrigger wheels that pivot bach for pulling and forward for mowing. the back of the machine would have a three point hitch. there are many good used three point  attachments like brush mowers, roto plows etc.

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