Introduction: Steerable Continuous Track Concept

In this Instructable, we will go through my adventure of designing and modeling a steerable track/tread (as in tank track). I will try and cover as much of the modeling and simulation steps as possible, I will try to communicate all the important information in the text but there might be useful tips and information in the picture annotation. I hope you can learn something from me here and I can learn from you too! so please comment (especially how to do things more efficiently with motion simulator)

So a little background on this project. (no important instructions here)
I recently started my internship at a construction/agriculture vehicle company (Kubota) and after speaking to a few of the employees there and looking through the catalogs, I learned that tracks that can be retrofitted to tractors are in high demand. The problem is the good quality ones are too expensive and the affordable ones very unreliable. The usual approach is to have a set of tracks for the front wheels and another set for the back allowing it to steer as usual.
So i thought to myself, what if we could have a track system that will be able to span from the front to the back and still be steerable. after making a few quick sketches and quick googling, i proceeded to work on the CAD model in Solidworks

The two main inspirations
https://www.google.com.my/url?sa=t&rct=j&q=&esrc=s... (never seen this)

http://en.wikipedia.org/wiki/Hyanide (Seen this many years ago)

*Regarding similarity to airport baggage carousels
https://www.google.com.my/search?q=airport+baggage...

Honestly, I am not entirely certain how airport baggage carousels or conveyor belts work in detail. From my observations, the movement is usually restricted to rotate about 1 axis. Airport carousels and sushi shop belts are usually flat (or at a fixed angle) and would allow the vehicle to steer but it would not wrap around the wheels. I would appreciate it if someone with knowledge on this subject can provide some input.


Few thoughts about this project/system

  1. I undertook this project mainly to gain a better understanding and feel for how tracked vehicles work, as well as to sharpen my skills with Solidworks and its motion simulation package.
  2. It is a very crude model, ease of manufacturing and upkeep is only lightly considered.
  3. Halfway through this project I thought it could be a good method for steering a single tracked vehicle like the Hyanide, I feel that the Hyanide's design would have poor turning radius and this method could do better

Some additional design criteria

  1. I made it a point to design the tracks such that stiff material may be used (such as metal tracks used by construction vehicles and military vehicles ) It can still accommodate rubber cleats for traction but flexibility must be due to mechanical linkage.
  2. The tracks must still provide advantage of lower ground pressure and better traction. The track is also designed to minimize damage to the ground, but maneuverability is prioritized.

Potential application for this system

  1. Retrofit to tractors
  2. Tracked vehicles that want to minimize damage to the ground (construction and landscaping vehicles)
  3. Single tracked vehicle, like the Hyanide. Could be used in rough terrain, snow, or maybe even on the water
  4. Military vehicles to improve maneuverability
  5. Robots, hobby or otherwise

Ps* If I can get my hands on a 3D printer, I can print and test out my design for a cute little robot.

Step 1: Designing the Track/treads

*UPDATE*
Since many did not notice the section i wrote on preventing sideways drifting of the track/track slipping off. I would like to note its on step 5. I have also added renderings with idler wheels and "suspension" since I know its TLDR (too long din't read)

The main difference over traditional track systems is that we need to be able to rotate a section of the track in an additional dimension to allow it to turn. Each link should have 2 degrees of freedom in terms of rotation.

I started with a sketch on how i would want it to work. Each link will be made of 2 parts where at one end we allow rotation in one axis and at the other end rotation in a perpendicular axis.

I name the part that will contact the ground as "Main Plate" and the part that allows for the additional flexibility is named "Pivot Plate"

The main plate will need to be able to pivot around adjacent main plates while maximizing contact with the ground. To achieve this, a semicircle is used for the front. To ensure that the adjacent main plate pivots correctly, the pivot should be located at the center of the circle. At the back, I made a "chopped off" semi circle, chopping off the tail allows it to turn properly (refer to picture).

As for the pivot plate, since it is closer to the "wheels" than the main plate is, it is also the pivot plate's job to allow for some interface that allows power to be transmitted to the tracks. The pivot plate is also going to have some interfacing surface with the guide rollers that we will cover later. The pivot plate is basically has one end that allows a main plate to rotate about an axis and another end that allows the next main plate to rotate about a perpendicular axis. It also has a large protrusion that allows the drive cog to engage it and turn the track, much like rack and pinion gears.

I also made a pin just to hold it together. But in hindsight, we can probably omit this pin to allow for faster computation in the motion analysis (will be covered later) since the mates defined will be sufficient

Step 2: Assembling the Track Optional: Solidworks Mate Reference Tips/simple Tutorial

If you are already proficient in assembling chains and tracks in solidworks, feel free to skip this step.

Initially I assembled one link (main plate+pivot plate+pin) and saved it as a separate file then I tried to assemble multiples of it together. The results were not satisfactory as I could assemble the track, but it could not rotate.

In order to assemble the track to the desired length quickly, I used mate references instead. Mate reference allows the parts to "snap together" when you hold them close together in assembly.

How to set up mate reference

  1. Open the first component/part file.
  2. Select "Mate reference", Found in Features>Reference Geometry>Mate Reference
  3. First name the Mate reference. *Important* make sure it is exactly the same as its counterpart in the next component.
  4. Next is to select the desired surface or edge or point and the desired mate type (default is ok, but not always the best) If you use surface or edge, you will usually need more than one mate reference, ensure the order of primary, secondary and tertiary mates are the same for its counterpart.
  5. Open the next component/part file.
  6. Repeat steps 2,3 and 4
  7. Repeat for as many components and mate reference you need.

Once you have your mate references set up, when you open the parts in an assembly file, they should snap together and automatically generate the desired mates when you bring them close together.

Step 3: Designing the Drive Cog/wheel

I am not sure what the correct term is, so forgive me please. Here its more of a story of failure, the few initial iterations did not work properly when tested with the motion analysis. So why would you bother to read about my failures? so you don't repeat them.

In the initial design, I positioned the tracks into a semi circle, drew a circle, drew lines from the center of the circle to the pivot plate protrusions and measured the angle of these lines. I then made the wheel and cut out narrow slits for the protrusions to interface with. The problem is that the spacing between the protrusions are very large unlike conventional tracked vehicles, this made it quite unreliable from the test i did.

Next I tried widening the slots and later i tried adding more slots but to no avail. Finally I took a different approach and instead of a solid block with slots, I made a Yo-Yo like wheel with plates.

To be honest, it works but its very poorly designed and I am not very satisfied with it. However it works well enough for a concept.

*The drive wheel could also use heavy trimming to reduce weight and material cost.

Step 4: Holding the Track in Shape

To ensure the track maintains its shape for operation, we need another wheel in front and a way to hold both of the wheels.

The design of the front wheel is pretty straightforward. The front wheel can be exactly the same as the drive wheel as some vehicle (some tractors) are 4WD. Here I used a YO-YO shaped wheel similar to the drive wheel but without the interfacing plates, this was done mainly to cut down on computational time.

The structure holding the wheels are a little more complicated. We will need to ensure that we are still able to steer the track since thats the whole point of this project. Also keep in mind, we will need some way to maintain tension on the track when the track is steered. Remember the hypotenuse of a triangle is always shorter than the sum of the other 2 sides.

There are many was to achieve this, here is what i did.
The rear bracket is "fixed" as in it will be attached to the vehicle chassis or will be the chassis and it is the reference point for all other parts. (The universe revolves around the rear bracket!!). The rear bracket simply holds the rear axle in place and provides pivot for the front bracket. The front bracket has a point that pivots about the rear bracket and a slot that holds the front axle. The front axle is held in a slot so we can place springs that act to maintain the track in tension.

In hindsight, for a design made to be retrofitted to 4WD vehicles, tension of the track should probably be maintained using a mechanism similar to a bicycle chain tensioner. If the front wheel is also a drive wheel for a non-single-track-vehicle, the vehicle's front axle should enter from the pivot and power the track's front axle through a gear system.

The rear bracket is very basic and can be modified. Some of the possible modifications:

  1. Made into just a frame that can be bolted onto a vehicles chassis for retrofit
  2. Made to hold additional idlers and suspension
  3. Made to hold flexible guides that can "shape" the way the track interfaces with the ground. (more on this later)
  4. Made into the chassis of a single track vehicle. (You can put your rider on top or even inside! but not under)

Step 5: Track Guides and Suspension System

The main purpose of the track guides are to ensure that the track will bend where you want it, how you want it. The design of the guides are very straightforward, it is basically something that holds a couple of rollers that restrict the tracks motion in certain directions (translational and/or rotational)

For the top guide, you mainly want the track to bend at the pivot, this is because it allows for the smallest footprint and would not allow the track to "cut into" the vehicle's body when steering, this also ensures that the tracks engage the wheels straight on and would be less likely to fall off. One of the simulations i performed without the guides actually saw the tracks fly off.

For the bottom guide, having the track bend at the pivot should allow for the best possible steering at the cost of some ground damage but I may be wrong as its a deduction based on intuition. You can and maybe should have multiple instances of the bottom guide modified to accommodate suspension springs and dampers. The bottom guide may also be used to "shape" the track into a smoother curve instead of an abrupt bend.

The rollers are basically donuts, its really just 2 concentric circles extruded.

Step 6: Mostly Done! Motion Analysis and Simulation in Solidworks

The track system is mostly done. Here I will share on my work trying to simulate the system steering while in motion. Here I wanted to see how it all works out and have a cool animation to show for my efforts, the values calculated and data acquired are disregarded as they mean nothing since I did not input any accurate data (like weight, density, forces, speeds) but its alright since its a proof of concept. To achieve all this, I used solidworks motion to run the analysis.

I will be very grateful if anyone is willing to share their experience on how to improve the computational efficiently. I basically learned all this as I went along.

You can also animate the assembly using the animation tool or basic motion tool, however I could not get it to work the way i want it to and solidworks motion was able to.

  1. You will need to enable solidworks motion by going to "triangle beside options">Add-Ins...>Solidworks Motion.
  2. Then at the bottom of your screen switch to the motion analysis tab.
  3. First we will define what parts are in contact and will not "phase/ghost/wallhack" through other parts. To improve computational efficiency, I used the group contact function. The whole track was placed in once group and the parts it comes into contact with (both wheels, guides+rollers) are placed in the second group.
  4. Another contact group was defined to contain the front bracket, front axle and front wheel. This is to prevent the whole thing from collapsing or the wheel from flying off into orbit.
  5. To simulate the spring holding the tracks in tension, I used 2 forces applied on the from axle relative to the front bracket. I used forces instead of actual springs because I am not sure how springs act in the simulation and experiments with it were not fruitful.
  6. Add a motor to the drive wheel to get it running and add a motor to the front bracket to see how it turns.I also added a large plate to act as the floor which makes it more realistic.
  7. Press calculate
  8. Do something else, its going to take awhile. After turning down the frame rates and accuracy it took me 7 hours to solve 3 seconds of motion.

Be warned, save as many videos of it as possible when you can. Solidworks crashed on me when i clicked "save" (happens everytime, hope its just me)

Extra Tip* It might be wise to turn the accuracy and frame rates down and test in successive complexities. What i mean by testing in successive complexities is that for the first time, just test a few links of the track with the drive wheel, then test the whole track with both wheels, next add in the tensioner force, then add in the steering motor next and lastly add in the floor.

Step 7: Thats It!

Here are some of the videos I could record before solidworks crashed on me. You can go to my youtube channel to look at a whole playlist of ill-sorted videos on this project

http://www.youtube.com/playlist?list=PLoUSuSQ_C_4V...

And a little extra rendered images

I hope you would have learned something from this adventure of mine. Please do leave a comment, especially if there is something you can teach me (and everyone who reads comments)

*Ps, vote for me! if I get a 3d printer, I will print this out (a more refined version) and test it!

Comments

author
nedash (author)2015-01-30

Looks cool! But I don't understand how the front wheel is maintaining track tension. I was a tank crewman in the Army, remember how much pressure was required to stop the track from coming off, and suspect that bending this would be impossible at full size due to that force. If it *did* turn, the design would throw a lot of dirt (spoil) between the track and the road wheels -- again throwing off the track. Might skid well on concrete, though.

author
michaelgohjs (author)nedash2015-01-30

Thanks!
To be honest, i have no experience working with or on tracked vehicles. So this is concept i was exploring. The feedback i got from people with the experience i dont (like you) has been very valuable. Thanks again =)

author
treyes4 (author)2015-01-29

I think you deserve the best tutorial for 3D Design contest..... I use sketch for fast/basic shapes but i've always wanted to try Solidworks with all the cool yet complex features

author
michaelgohjs (author)treyes42015-01-29

Thanks! thats very encouraging
I have a new tutorial coming soon, and i think its a pretty cool concept i would like to share with the world (Coming soon)
There are lots of great tutorials on youtube and online in general.
If you want to take up Solidworks go for it! just dont be discouraged when things mess up, it can get frustrating

author
jackowens (author)2015-01-01

So basically you want to make something like this: https://www.youtube.com/watch?v=tKJIbaEKa3o&index=4&list=FLBW6iUud7RuKw0siaWxRiLg

author
jackowens (author)jackowens2015-01-01

It's called the MTT-136, it looks kinda like what you have in mind

author
michaelgohjs (author)jackowens2015-01-02

Hi, it looks similar. However what I have in mind is also able to pivot at a point to allow the track to steer.
Thanks

author
jackowens (author)michaelgohjs2015-01-02

Yeah that's a really cool idea. Just thought I'd share that video, still very interesting stuff :)

author
michaelgohjs (author)jackowens2015-01-02

Thanks for sharing, its a nice video. Good to see how its done in the industry

author
XenonJohn (author)2015-01-02

In the second world war there was a UK light tracked vehicle called the Bren Gun Carrier. It was unusual in that it had a steering wheel that could warp the tracks to some extent making it much easier to turn at speed than a regular light tank.

Apparently there was an instructor who used one on a UK tank training range until recent times, as it was fast and could cover ground regular modern 4x4 off road vehicles could not.

Might be worth you researching how its tracks were designed.

author
michaelgohjs (author)XenonJohn2015-01-02

I have only encountered the Bren Gun Carrier in Company of Heroes 2 (a PC game). Did not know it was such and interesting vehicle, thanks for the tip =)

author
wilcorp70 (author)2014-12-25

Ok, I designed a similar system for an experimental rover in college. We used an off the shelf conveyor track since the speeds were fairly low. They make conveyors that flex the way your model does in both steel and plastic. The conveyor will wrap around the wheels just fine as they are meant to do this. You can find these pre-made systems inexpensively by searching ebay for side flex table top chain. Rexnord makes a lot of them (it is what we used) and they have solidworks models on their website for all of their chains. You could also learn from the sprocket design they use for this type of chain. It is similar to the slotted design you have but instead teeth are rounded trapezoids. This prevents a lot of the binding it looks like you had with your design. At the very least it should provide some good ideas about how this mechanism works in industry.

author
michaelgohjs (author)wilcorp702015-01-02

Thanks for the input, as you say its always good to see how its done in industry where lots of time and effort (and money) have been put into developing it.
Looking it up now =)

author
astrong0 (author)2014-12-10

This is amazing but.... the only issue is see would be turning. if you curve the track and the track forms a curved path then the 'cycle' would tip over because there is no way of over coming the vector force of the entire moving body. You would either need a set of training wheels located in the middle or have the front wheel equipped with some sort of roll.

author
michaelgohjs (author)astrong02014-12-10

Yup, turning and side force is one of the main challenges here.
Interesting, did not consider that aspect of it. Thanks for your input =)

author
mikeyc.2009 (author)michaelgohjs2014-12-24

Since the track links can pivot in reference to each other then maybe you could tilt the road wheels to counteract the side forces like high-speed trains do going into bends. This would mean that the large idler wheels at the ends will have to be raised. Or you could just tilt the external body in reference to the entire track system. This would be a much less elegant solution.

author
astrong0 (author)mikeyc.20092014-12-24

A much less elegant solution for a much more civilized time?

author
mikeyc.2009 (author)astrong02014-12-24

If you try either one of the solutions that I mention I hope it is the first one so that the entire system moves instead of just tilting the body attached to the track system. IMHO merely tilting the body that would be attached to your track system would be much less exciting. It is great to see people trying new things that the other billions of people have not even thought of. Good job.

author
michaelgohjs (author)mikeyc.20092014-12-24

Very interesting ideas, never thought of that, would have to look into it.

Thanks!

author
astrong0 (author)michaelgohjs2014-12-11

Perhaps a convex tread? Maybe each track plate is about a foot wide and drops I'm the middle about four or six inches? Maybe I could do a quick render in Blender in the morning.

author
michaelgohjs (author)astrong02014-12-11

Ya, a convex track might be the way to go about it, but its hard to tell unless we test it out =)

O.o that would be nice, tbh i have no idea how to work blender, never even tried

author
astrong0 (author)michaelgohjs2014-12-12

Okay so my renders are not as pretty as yours but it is simply to show a concept and because it 330 in the morning for me. I also redesigned the middle pivot to look like a hem (Heem?) joint and the curved tread. The bar between the pivot cups is mobile and free to rotate within its limits. I am an Arts major not a Mech. Engineer so i don't know if this is plausible or not.

Instructable Pic 1.pngInstructable Pic 2.pngInstructable Pic 3.png
author
michaelgohjs (author)astrong02014-12-12

Very NICE! great job man. I just got back from office too, but its 6:30pm here.
Looks great overall, but the middle joint might not be too suitable. I imagine the joints allow the tracks to roll (as in do a barrel roll) but would not allow the required turning.

Really appriciate your work =)

author
astrong0 (author)michaelgohjs2014-12-14

I just realized the Star Fox reference.

author
astrong0 (author)michaelgohjs2014-12-14

I just realized the Star Fox reference.

author
astrong0 (author)michaelgohjs2014-12-12

Hmm it is quite the conundrum.

author
astrong0 (author)michaelgohjs2014-12-12

Just got off work at 1250am. TO THE BLENDER!!!! Or would it be just to blender? Anyway I'll see what I can do.

author
Edgar (author)2014-12-12

This is a great How-to for Inventors wanting to bring their Ideas to life! :D

Gone to my Blog:

http://faz-voce-mesmo.blogspot.pt/2014/12/blacksmith-uma-3-em-1-3d-e-uma-mono.html

author
michaelgohjs (author)Edgar2014-12-12

Really neat blog, thanks for sharing.
(but i can only read the english parts =( )

author
Edgar (author)michaelgohjs2014-12-12

Just turn on the Facebook translation :)

author
cford79c4 (author)2014-12-12

just one thing, on your track guide there is some flat surfaces that come into contact with the rollers on the track guide fron the front in Run test 7 5 and i just thought maybe you should add a fillet or a curve to minimize wear and jamming potential.

otherwise this is awesome

author
michaelgohjs (author)cford79c42014-12-12

Oh thanks for pointing that out. I miss lots of stuff after hours of solving
=) thanks

author
cford79c4 (author)michaelgohjs2014-12-12

you're welcome :)

author
actimm (author)2014-12-09

A few comments on this.

1) Tank/bulldozer/snowmobile tracks actually have a pin and hinge system specifically designed to keep them running in a straight line. If it was able to twist too easily, the track would come off the wheels.

2) A company a few years ago was experimenting with this idea and they were able to make a concept snow mobile bike with it, but the tracks they used had a kevlar rope for the hinge link and actually needed to make both the front and the back turn just to be able make it corner at all.

3) It is a really neat idea and possibly using a variant of that giant amphibious transport's tracks would work if you could scale it down. They used a hinge system to allow it to provide propulsion in the water but then when it was on land, the track pads just laid on the ground. That may give you enough flexibility to allow the angles of motion when running and turning.

author
michaelgohjs (author)actimm2014-12-09

Thanks for giving your input.

I looked at a few bulldozers and excavators and modeled my hinge on the back of the "main plate" similiarly.

Thats really interesting, if I am not mistaken the the patent I linked in step one also mentioned using a cable as the "backbone".
Oh, so it needs both the front and back to turn, hmm.. did not know that. I would have to build a model to test that out.

Thank you =)
Ya, I thought about that for an amphibious vehicle, have some flap like paddle that can fold up when on land on each track. Was wondering if that would make it impossible to reverse in water. or if the paddles are simply hinged, it might snap off when caught in a bad position and failed to close. Arhh, I am getting carried away. Time to research that giant amphibious transport you mentioned.

Thanks again for your input =)

author
madvic (author)2014-12-09

Hi.!!

Good one ..!!

But I guess you ought to patent it!! I will vote for you..!

author
michaelgohjs (author)madvic2014-12-09

Thanks!
I would really like to do that, unfortunately i dont have the know how or the financial firepower to service patent duties and what not. Besides, I would like if fellow makers and tinkerers were able to bring this design to the next level without fear of legal flak

author
LynxSys (author)2014-12-09

This is a neat idea, and a fun intellectual exercise. From a more practical standpoint, I worry about the sideways forces on the track leading to maintenance difficulties, as well as the possibly limited turning radius (unless you intended to use two of these on a vehicle that could also be skid steered). I'm curious to hear if anyone can think of a practical application for this design that would not be equally well served by a pair of two smaller, independent tracks in line, with the front track being steered (like you see on a truck with Mattracks, for instance)? To be clear, I'm not knocking this Instructable in the least, I think it's very cool! I'm just trying to think of practical applications.

author
kbc2 (author)LynxSys2014-12-09

The side force in the turns is what I was worried about as well. I have operated four wheelers and UTVs with track systems and have had the tracks come off in a turn. Maybe a pivot in the tracks may help. Can I be the crash test dummy for the full scale model??????

author
michaelgohjs (author)kbc22014-12-09

Well, you have the experience of operating similar vehicles, so if/when we have a model you can be the "test pilot of experimental system" but if you insist on being the crash test dummy, hope you dont mind load cells taped all over your body =)

author
michaelgohjs (author)LynxSys2014-12-09

Thanks! I am proud to have produce something that stimulates much intellectual discussion.

Thanks for the feedback =), will look into the details of it.
Its always good to be practical, even for a concept it still has to be grounded in reality and practicality.

author
jdunk67 (author)2014-12-06

That's awesome but how will the track stay on when turning?

author
michaelgohjs (author)jdunk672014-12-09

Added images with the roller/idler just incase you dint read the text in step 5 (i know its too long)


Notice the front-most roller/idler is slightly different to deal with loads in the Y and Z direction (assuming track is long in the X direction).

*The front-most roller was already there and discussed in the ible, but view of it is quite obstructed

author
kbc2 (author)michaelgohjs2014-12-09

I got ya. I am a visual person, between reading and trying to fully visualize ....I was missing something. Maybe I was visualizing something different. Would be awesome to see a working models in person.

author
michaelgohjs (author)jdunk672014-12-06

The tracks are taller in the inner portion and fit into the groove of the wheels. The use of the guides should also help.

author
grapenut (author)2014-12-09

I think you should design and build a toy sized prototype; and market it as a toy. After a few years of upgrading the original and workig out the bugs; you might have something really great!!

author
michaelgohjs (author)grapenut2014-12-09

Haha that would be a nice way to go about it! never thought of actually marketing it as a toy. Maybe just a small RC toy to start with?

author
marshall p (author)2014-12-09

I think that to alleviate most of the sideways friction you would have to design the track system to bend along it's entire length not just in the middle . This way the system won't be fighting itself and you will have better traction . Maybe by driving the track by a wheel above the track/ground area it would be easier . I'm thinking of a triangle type of drive like on the quad trac tractors that case have out .

author
michaelgohjs (author)marshall p2014-12-09

Thanks, thats a great idea, I was considering that. That would also further reduce the damage done to the ground when skid steering. Something like a gradual curve all the way from the front to back.

Sadly i am too lazy to draft out a mechanism and implement it in solidworks. but it could be similiar to that in the patent link i posted (step 1)

author
suicidal.banana (author)2014-12-09

Nice idea, and props for working out the details! :)

However, im sad to say this likely wont work, unless you make the whole thing out of titanium. If you think about the weight of the 'bike', and that it should be able to steer at speed, you'll soon realize that the sheer forces involved are huge, and likely to either rip apart the track, or break the 'arms' that hold it in place.

That said, i really hope im wrong making the above assumption, and i would love to see you take it a step further (a working model maybe?)

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