3D Printable Track Design
A visitor to the site -- t00tie -- sent over a link to a very cool 3D printer model for plastic tracks.
The model is called "Moon Rover" created by emmett on the site Thingiverse. The track design is derived originally from a expanding bracelet and it utilizes the pliability of ABS with the natural flex of the deep inset hinges between each cleat to get a simple yet effective tread. Apparently, the cogs at each end nicely mesh with the hinges and provide positive traction.
I like that this photo shows the extruded strands of ABS stacked to make up the track width. It looks to me like the design would also allow for some springy suspension properties, too. However, power capacity in a larger scaled up version may be an issue as the tread will stretch and deform under stress.
Timbersled Motorcycle Track Conversion Kit
There have been a number of tracked recreation vehicle designs popping up lately pushing into an interesting area of hybrid conversions. Specifically, these are kits designed to convert an off-road motorcycle into a uniquely capable snow machine. There are many companies, however, Timbersled is a popular kit out here in the mountainous West Coast of Canada.
The benefits are many when comparing to a dedicated snowmobile:
- If you already own a dirt bike you can take advantage of this existing machinery to gain extended usage during the cold snowy seasons. Kit bolts onto your bike with no modifications and fits late model dirt bikes that are 250cc and larger (450cc recommended).
- The weight is much less than a snowmobile (about 300 pounds with bike), and the narrow compactness translates into a much more maneuverable carving experience for the rider. The narrowness also means increased access to tight areas such as dense forest and traversing steep hillsides, and an easier time digging it out of a snow bank if it comes to that.
- Its a universal kit, which means you can mix and match with different bikes; and it retains its utility even if you upgrade to another bike or make major modifications to dial the bike in to your own tastes and fitment.
Some of the criticisms of this system compared to a snowmobile are:
- Much less power in a dirt bike engine compared to a snowmobile, and therefore speed, hill climbing, and deep powder performance is significantly decreased.
- Cargo capacity, passengers, and other utilitarian applications are severely limited, or not possible, with the bike compared to snowmobiles.
- Efficiency and range are limited, especially in deep snow, which makes the bike conversion more of a toy than a transportation tool. The narrowness means it is unstable on ice, which is problematic on slopes with painful consequences.
I think its a nice application of track technology for the recreational crowd, and it serves a niche for dirt bike riders who want to play in the snow without all the size and cost of a snowmobile. It looks like a lot of fun, with softer falls than in the dirt and rocks, too.
Omni-Crawler Track Design
This innovative track design from Japan's Osaka University allow a vehicle to carry heavy weight and gain the advantage of multiple directions of travel.
The design uses interesting split track layout mounted on wheels they call omni-balls -- spherical balls split into two hemispheres -- as the drive mechanism for the track. It appears from the video that the drive shaft attaches to the front and rear of the track mechanism and this supports the weight of the vehicle and transmits power and control inputs to the track.
My take on this is that the shafts attached to the front omni-ball and the rear omni-ball are independently controlled. When they rotate in the same direction, the track engages in a caterpillar motion like expected. When their direction is opposite rotation, the track rolls sideways like a cylinder in a "log-roll" motion. These two motions can be blended to get a combination effect.
Careful review of the pictures also suggests that each half of the track cleat is attached to a common bicycle chain. There is likely two chains, one for each side of the track, to provide structural connectivity and allowing an open channel that doesn't interfere with the shaft access to the axis of the omni-balls.
I like the idea of multi-directional control of movement, and the claim that this is much more efficient than maneuvering a vehicle with a traditional track design. Efficiency and mobility are strong pluses to any drive system. And, that it retains low ground pressure characteristics and traction potential is good, too. And, lastly, if you're looking for some wow-factor bling to your project, this design also delivers on that front.
Skizee Tracked Pusher Vehicle
Just stumbled upon this site about two guys, Tim Park and Jim Maidment, from Kimberly BC Canada who made a tracked vehicle they call the Skizee. Intended for ski patrol and back country skiiers to gain additional mobility and range in their activities.
The Skizee is powered by a 10.5 HP 4 stroke engine wrapped in what looks like an off-the-shelf snowmobile track -- a design reminiscent of British Mark V tank from WWI. The vehicle has a rigid single side arm that pushes the rider and provides grip handles and throttle control.
The experience for riding this vehicle looks like fun, although more on the utilitarian side of the fun spectrum. I like that the Skizee provides a skier with additional speed, range, and maneuverability with a minimum of equipment. And especially that it could function like a one-person ski lift while exploring the back country.
All Terrain Tracked Motorcycle
As part of our brainstorming session, Greg and I discussed the possibility of a single tracked bicycle design where the track could flex into an arc for the purposes of cornering. Turns out, a couple of crafty German designers, Tilmann Schlootz and Oliver Keller, thought of this long ago and in 2006 released a motorcycle model for the Michelin Challenge Design competition.
This is the Baal high performance design and its an awesome looking vehicle unlike anything I've seen before. Apparently the front and rear wheels both pivot (the rider uses both hands and feet to turn) and the track flexes to turn. Notice the two track placement rollers in the center look to ensure proper track arc alignment. The rollers pinch a center spine from the track and pivot opposite to the wheel to bend the track into an even arc during cornering. They also likely help distribute the weight of the vehicle for even ground pressure. The claim is that this track design has benefits in floating easily over soft surfaces such as sand, snow, and mud.
I'm also amazed by the mono-shock suspension and geometry of the front and back pivot arms. The frames look to be very similar to modern motocross motor bikes and likely accept similar sized engine and transmissions. Like most tracked vehicles, however, I'm thinking that the high speed handling characteristics are likely difficult at best. And, the added weight and drag of moving the track would decrease the efficiency of this ride. I'd guess the riding envelope would be on par with a large 4x4 ATV -- a strong performer in slow to medium speeds over difficult uneven terrain.
I see this as being an excellent idea that I'd like to try out. Unfortunately, there are no plans at this time to put them into production.
Small Motorized Tracked Vehicle
Interesting find on the web -- the DTV Shredder motorized personal track vehicle. The prototype was designed and built by fellow Canadians BPG Werks located in Brampton, Ontario. They claim to have financial supporters for civilian and military applications and expect to be in production in the next 18 months or so.
A couple of points worth mentioning:
1) the tracks look very similar to the ATV aftermarket products available. The rubber track and plastic sprockets is a popular choice, and in addition, some suspension is built in to provide impact absorption and terrain following.
2) The video and picture seem to show two different motor configurations. The first is a 14 HP Honda 4 stroke air cooled engine common to a variety of lawn and garden equipment. This can be seen as the red cowling in the top image. The second appears to be a small 2 stroke 125cc engine from a motorcycle as evidenced by the small muffler shown on the bottom left image.
The video implies, and my intuition suggests, that the torque of the 4 stroke engine is the essential ingredient in this package and likely performs better than the small 2 stroke engine. However, the additional weight of the 4 stroke as compared to the 2 stroke likely has a negative impact on the handling of the vehicle. Interesting to find out their experience and what decisions are made for the production models.
3) The video shows how agile the DTV is and how smoothly it corners. The controls appear to be based on weight transfer on the foot platform used modulate the left and right track speeds via a torque converter or similar mechanism. The upright handle appears to be for maintaining rider stability and operating the throttle. The riding position makes me think of a stand-up jet ski with tracks.
Check out the video of the DTV in action below.
Golf Cart Frame Up and Running
We have found an old 3 wheeled golf cart and rebuilt all the required parts to make it a reliable machine for this year's Burningman event.
This platform has a good gas motor, large electric starter/generator, and solid variable speed transmission. Next year, we plan to remove the rear wheels, extend the back, and add tracks.
It's hard to look too serious while riding a 3 wheel golf cart with red fun fir seats . . .
Home Made Track Build
Discovered this page where some robotics enthusiasts made their own tracks out of bicycle chain, PVC pipe, and bolts. Looks like an effective design and I'd like to see it in action!
Tank Tricycle
Given the constraints of managing steering and traction, Dave and I have settled on a tracked tricycle design similar to that used in WW2.
Local Students Make Pedal Powered Track Vehicle
I saw this in the Globe and Mail and had to post it here:
I really like their concept and the simplicity of the design. Seems like they used a snowmobile track, cut in half down its length, and all the stock drive cogs and idler wheels. Bicycle pedals and frames welded on to a square tube chassis rounds out the package. I'm curious to know how well it works and to talk with these guys... If you're out there drop us a comment!
ATV Track Examples
Found some smaller ATV track examples. Similar to the car previously posted, however, smaller. One attractive thing about this design from a human powered vehicle perspective is that we would no longer need to utilize the skid-steer method of turning, which is inefficient and difficult for a load capable track design. In this ATV example shown below, the tracks in front steer independently and the rear are fixed.
This is a photo of a 6 wheel ATV (4 in the rear and 2 in front) converted to tracks. These conversion kits are promoted as excellent for snow, mud, and sand use, and depending on the track, also good on hard surfaces. They offer improved traction in soft terrain because they spread the weight of the rider and vehicle over a large contact area to prevent sinking into the terrain. Notice the front tracks tend to be shorter and center the weight over a smaller area under the main cog (where the tire used to be) in order to improve handling and allow easier turning effort. The rear tracks tend to be long and flat for maximum traction and cargo capacity.
This video shows the "Commander Wide Track" ATV tracks in action and demonstrate that performance in snow and hill climbing are exceptional.
This image shows the Camoplast ATV track conversion kit with some specs and dimensions.
The Litefoot Track includes internal suspension and pivot arms to provide additional flexibility.
Rubber Timing Belt as a Track
Found a belt on the McMaster-Carr website that may serve as a good rubber track for the project.
It is a double-sided timing belt with traction ribs on both sides. Its 1" wide and 81 3/4" length (longest option). Seems like an interesting option similar to the other rubber track examples.
One unknown is how to mate this type of track with pully or bicycle rim.
| Part Number: 7891K125 |
$114.10 Each
|
Sketch of Overall Design Concept
Notice the cab-forward position of the driver(s) who also pedal the vehicle. The mid section is two doubleseat benches positioned sideways for the passengers (tentative seating plan) and a gear section to the rear where the sketch shows a cooler and radio.
8 Wheeler Concept
Dave Montie and Greg Montie's 8 wheeled ground following track concept.
A late night Lego session lead to the creation a number of possible track designs. This one ended up a likely candidate for our goals:
Next, Greg did some 3D computer modeling of the design:
Each of the 8 wheels will be bicycle rims and each set of two wheels is joined by arms that themselves pivot to follow the irregularities of the terrain.
Riding Lawnmower Transaxle Option
Some other human powered vehicles recommend using a transaxle from a riding lawnmower to put the power to the ground.
The main benefit is that the component comes with a differential, several forward gears, a reverse gear, and sometimes even a brake all in one package. Apparently, they are very efficient and cxapable for the type of power requirement that a couple of people pedaling plus some assist can generate. Notice that the majority of these units are driven by a vertical shaft on the top. This is usually mounted with a pulley and belt drive to the engine. Not the most ideal for our design -- we'd prefer a horizontal input shaft --but it can still work.
Another major bonus is that we have a reliable source for used lawn and garden equipment -- our dad -- that can make this an even more appealing option.
Super High Rolling Efficiency Concept
This is Greg Montie's concept of a high rolling efficiency track.
The idea is to have a single V-belt for low weight, and a high efficiency linear (smooth) roll motion. A chain of aluminium cleats are riveted to the V-belt to complete the track. The cleats wings are curved to the diameter of the pulley wheel. This makes for a smooth rolling surface for the pulleys to travel on.
The cleats are made from 0.032" (or 1/32") aluminium. This aids in weight reduction and allows for each cleat's connector tabs to flex while following the V-belt around the pulley wheel. The cleat wings are not very strong as they are cantilevered on either side of the V-belt. However, the strength is improved by the general curved shape of the cleat. Furthermore, each cleat wing is protected during its most loaded duration - directly under the pulley wheel that carries the majority of the vehicle weight. This is accomplished by welding drums on either side of the pulley wheel, of equal diameter, that directly support the cleat wings under load.
3D File can be found here: 09-09-25 Assembly
Remote Controlled Tank Examples
Here is a link to a very detailed R/C Tank website that discusses a variety of options for building tracks. Below are 7 methods illustrated:
Bicycle Chain Track
This method has good traction and drive characteristics and affordable to build, but is heavy and the chains easily twist which creates a tendancy to derail.
Treadmill Track
This method uses an old treadmill track (stationary running machine tread or industrial conveyor belt) as a continous link medium with wood or other material attached as treads. This is an affordable option, although hard to source used, relatively lightweight and efficient. However, it is friction drive which requires careful tensioning of the track or slippage and also a cog/pin mechanism to maintain alignment. Good potential to scale for this project.
Roller Chain Track
Similar to bicycle chain track except this has a single chain with flanges built right into the links. This type of chain is also resistant to bending or twisting which makes it resistent to derailing. On the down side this is the heaviest track designs, is relatively expensive, and is not as efficient as some other options.
Plastic Conveyor Track
This is a ready-made option where plastic track is used in industrial applications such as food processing. The nice part is that this track is very light and efficient, however, it is also the most expensive and lacks traction on hard surfaces.
Molded Track
The issue here is that you can make a mold for a track link and cleat, and cast as many identical copies as required. Good side is that you can make it any size as required, downside is it is an extremely labour intensive option. Also, it is likely a heavy and not-so-efficient depending on choice of materials.
Hinge Track
This method used regular door hinges and strings them together into a continuous track. This is an easy and relatively inexpensive option, however, it is also very heavy and low efficiency.
Chain and Bolt Track
This is a hybrid approach combining bicycle chain and bolts. It is low cost and very reliable, however, very heavy.
Conclusions
I'm thinking that the treadmill option is most likely where we should look. It seems like metal tracks are going to be too heavy for our application especially for riding on the road. Another option not dicussed here is to use industrial V belts and pulleys to create a track system. More on that idea...
Track Conversion Kit for Bicycles
Article from the Star describes a conversion kit that turns any mountain bike into a snow capable mode of transportation.
And another image (via autobloggreen)of the conversion kit that also includes a from ski to replace the front wheel.
What I like about this design is that it demonstrates an efficient pedal powered track system is possible -- specifically the narrow flexible rubber track seems to be the key here.
Notice the design doesn't force the track into a sharp radius bends at the rear idler cogs like the previous post. And I notice that the drive wheel seems to be solid plactic (not an air-filled tire) with sprocket style nubs that enmesh with the track to ensure positive alignment and drive characteristics. Both of these characteristics seems to optimize efficiency.
Lastly, I notice a detail that is obvious only when comparing the two photos: The rear idler assembly (3 cogs located behind the main drive wheel) pivot under power. The bottom photo (bike stationary) shows the rear idler down. The small idler in the middle seems to be touching the ground and the larger idler at the rear is actually raised off the ground slightly. I think this is to shorten the track contact patch and facilitate turning (A point Greg has mentioned previously).
On the top photo, the rear cog assembly seems to have rotated and raised off the ground a considerable amount under the power of the rider. I'm guessing this is for the purpose of some built-in suspension qualities, or terrain following capability for the track, or perhaps it is a variable mechanism to improve the handling characteristics depending on power output.
It looks like additional power from the rider turns the track and induces a secondary effect of driving the little idler down to make the track have a longer contact patch with the ground. I imagine that under hard pedaling the track bites down to provide more straight-line traction. And under less power, the rear cogs rotate back up to reduce the contact patch and increase maneuverability.
So based on this I'm thinking a narrow rubber-based track -- using v-belts? -- with solid cog style wheels may be a good way to optimize efficiency for our bulldozer application. Not sure if the variable rear cog system for handling is useful for our two-track application yet.
Human Powered Tracked Snow Vehicle Example
Here is an interesting patent for a snowmobile style human powered track vehicle.
Some positive points that come to mind:
- Recumbent position for the rider and the seat looks good
- Simplicity of chain drive mechanisms taken directly from a bicycle
- Center of gravity looks to be positioned close to the front of the track - matches the requirement for easier turning of the track according to Greg.
Some negative points:
- Slider on track (201) seem too high friction for our intended use.
- Complexity of idler gears throughout the chain drive
- Don't much care for the look of such a small wheel at the rear of the track
Kick-Off the Project!
Here is our first post introducing the project.
Stage 1: Collect ideas and examples from the internet.
Stage 2: Design and document our own plan
Stage 3: Begin the build
Stage 4: Testing and revisions
Stage 5: Demonstration!