Most efficient snowmobile track? Lowest durometer?

[NouvaNouva]

I'm taking part in a university project where we are building a robot weighing about 500 pounds. This robot will be running in the snow and have tracks on both its sides (tank style). The robot will run on solar power and will only reach a maximum speed of 5 mph.

We are looking into running snowmobile tracks on this robot but most of them seem to resist flexing and offer too much rolling resistance. What we are looking for is the track that will take the least energy to go around our track system. From what I've read it seems that I want a very soft durometer track, but I've little experience with snowmobiles. What would be the most efficient (least rolling resistance) track to run on this robot?

Note1: The longer the track is the easier it will be for us to incorporate it into the design.

Note2: I've experience working with cars and access to a good machine shop.

 

[tdbaugha]

We run a Camoplast Cobra track on our SAE clean snowmobile challenge sled. I've been told it is the lightest and will be the most efficient. It's only a 121" though.

If you want a longer track, I would suggest getting a 141, 153, or 162 inch Camoplast PowerClaw. Cut the track lugs down to you desired size since they are 2.25 inches stock. You can also port the track with 1 1/8" holes to decrease weight and rolling resistance.

Both these tracks are 15 inches wide stock. Since you're only going 5mph, you could cut away a lot of the stock material and still be very durable. Contact Camoplast, they may be able to tell you where and where not to cut away material.

 

[NouvaNouva]

Thanks! And just a few more doubts...

Wow! Man, you are exactly the right person to answer my question! Your experience building competitive snowmobiles proves that you know a lot about efficiency. Thanks for answering my post so quickly and accurately

Me and a teammate looked up the tracks you mentioned and we'll probably be going with the Cobras. We will look into porting the tracks but will have to consider weight loss and less rolling resistance vs. less surface area on snow (more sinkage). Sinkage (and the corresponding power required to advance) can be calculated through Bekker's equations, weight is a relatively straightforward thing to consider BUT we have no way of calculating the change in rolling resistance from porting. That makes the porting desicion a hard one.

Do you have any suggestions (mathematical or empirical) as to power savings in rolling resistance after porting? In your experience does a track sink more into the snow after porting?

We have three other questions and would be very grateful if you gave us your advice:

We found the Cobra track going all the way to 146X15 inches. Do these longer models have the same properties as the 121" Cobra track you suggested? (they are about 4lbs heavier though...)

It seems like we could save alot of weight by removing the track clips. Would you recommend this?

Does the pitch of the track affect efficiency?

I will write an email to Camoplast tonight, but I really appreciate your input as you have experience in designing a snowmobile for maximum efficiency.

Important links:
http://www.camoplast.com/tracks/tracks/cobra.html

 

[tdbaugha]

It depends on where the machine will be going. Since you're only going 5 mph, porting the track will probably have negative effects. Although, if you are running in hard snow(down a trail or something,) there will be plenty of surface area to support the weight. Just don't port the track if the machine will be running in deep powdery snow. Snow will push up into the holes. Another thing to consider is the size of holes you port. If you port a lot of small holes and you're running in wet sticky snow, the snow sort of acts as if it has surface tension and will gap out these holes if you know what I'm saying.

Track pitch does not have anything to do with efficiency. That is only the center to center measurement of the "windows."

All cobra tracks should have the same properties no matter the size.

Removing the track clips is a maybe. The clips are what slide on the hyfax on a snowmobile. There is less friction between metal plastic than there in between rubber and plastic. What I would do in your case is remove all the clips and place many small (idler) wheels between your robot and the track. The wheels will have the smallest coefficient of friction for sure.

Also, what you can do to decrease rolling resistance is to run the track as loose as possible without it skipping on the drivers. You would be amazed at how much harder it is to spin a track by hand if it is very tight around your drive system compared to it being loose.

Hope this helps.

 

[Scott]

How wide of track do you want?
You might consider hether you need a narrower track of the snowhawk.
What are those? 12" or 13"

Maybe that's not what you need...just something to consider.

As for lug length, at the speed you are running, the more surface area touching the snow the more rolling resistance you have. On harder snow or even solid ground, the longer lugs with stiffer durometer might not rob as much power, increasing efficiency.

While the effect might be lessened at slow 5mph speeds, soft durometer lugs will take a bit more to get the machine moving...more rigid lugs (higher durometer) would make sense to me. At 5mph traction and trenching is not the issue.

It's like when a rigid frame bicycle is more efficienct at getting the horsepower to the wheels than a softer frame. When you stand on the pedals, you don't want your suspension shocks to suck up all your efforts when you are climbing a hill.

 

[NouvaNouva]

Thanks for your input. New ideas and doubts

Thanks for sharing your experience tdbaugha and Scott (or should I say "The Stig"?). Your inputs have been very helpful and instrumental in the way our track design is developing.

In a previous design we used Camoplast "Ice Oval and Lemans Series" tracks. The vehicle worked but we found the track to be too stiff for our purposes. Even while lifting the vehicle off the ground it still had considerable rolling resistance. Is the Camoplast Cobra noticeably more flexible than the Camoplast Ice Oval racing track we used before?

I looked at the suggested Snowhawk tracks. I actually found them very interesting. I'm considering whether we should go more extreme than 12" width though. I'm very curious about the tracks used on the Hawk Jr. 60. That vehicle has just over 5hp and uses a 6.5"x91" track. Being such a low powered vehicle I'm assuming it has a pretty flexible track. Is this assumption correct?

If we were to so drastically reduce the width of our track we would need to increase the length too (and probably lose some chassis weight as well). Is it possible to cut up two tracks and then stitch them together end to end to have one double length track? Do you have any tips for doing this? I think it might be feasible to create a relatively strong union when considering our robot will deliver only <1hp and that must be divided among two tracks.

I'm going by the following idea: assuming the same surface area on the ground, the track with the least width would compress less snow and thus waste less power. If that concept works in practice then the Snowhawk 6.5" tracks, though unconventional, might help improve efficiency if we are able to increase their length. What are your opinions on that?

Thanks again for your help and I hope you get a chance to answer once more.

William

 

[NapaMatt]

My .02..


Go with Length NOT Width of track.. to Gain Floation..

To be able to turn, this Tank! It will be easier!

There are staples you can use to attach two track to make one.. Kinda like the huge freight staples..



PS Keeps us posted on what you really find that works..

 

[tdbaugha]

What is the weight of your robot and what kind of snow conditions are you running in? Will you have to go up any hills?

These need to be answered for us to give any more good advice.

 

[NapaMatt]

... the weight he said is 500 LBS

 

[NouvaNouva]

More information on robot and terrain requirements.

Thanks for your advice NapaMatt! If we join two tracks with large staples would that part of the track roll smoothly around the idlers and drive sprocket? Are there any tricks for joining the tracks with staples to retain good flexibility?

Sorry for not including more information on the robot. The 500lbs weight was a rough estimate from the one we built previously using the Camoplast Ice Oval Racing tracks. That robot weighed around 470lbs depending on the trim used. The new robot should be smaller and more efficient, we're now aiming for a final weight close to 350lbs. We are designing to try and have the robot produce between 0.3 and 0.5psi of ground pressure (assuming evenly distributed weight), closer to 0.3 psi would be better.

The robot should be able to run on soft or hardpack snow. We are designing mainly to run in snow with a density of about 15 lbs/ft^3. We expect to only go up slopes of a few degrees (definitely no steep hills). The snow we plan to run in is fairly flat and undisturbed. We expect to occasionally encounter snow ripples (soft and hard) around 8" high. The robot should run smoothly in temperatures close to 5°F.

The robot will produce a constant 0.5hp between it's two electric motors, in demanding situations they should deliver closer to 1hp. We want solid, dependable and very power efficient tracks that would allow the robot to run several hours everyday with no problems all through winter.

Thanks for your suggestions and advice.

William

 

[tdbaugha]

OK.

I think you will be better off with longer and narrower as opposed to short and wide.

This is just me thinking to myself but I think you can reduce your surface area quite a bit without the robot sinking in too much. Although, if the robot is top heavy then you wouldn't want to take that chance and have it tip over.

Just me thinking out loud.

I don't know too much about joining tracks end to end. I do know that you can run them through a table saw to cut them to a desired width. Many people have done it before with much larger tracks than a 146 cobra.

 

[X2Freeride]

My .02..


Go with Length NOT Width of track.. to Gain Floation..

To be able to turn, this Tank! It will be easier!

There are staples you can use to attach two track to make one.. Kinda like the huge freight staples..



PS Keeps us posted on what you really find that works..

They arent freight staples per say. But they are fairly similar. Much harder though and you need a tool to put them on... A rod runs through the middle to attach them together. The use offset spacing and slide together then the rod runs in the middle. They were/ are used on implements to attach belts together. Things like hay bailer belts together and swather canvases. Any implement dealer. IE John Deere or Case will have them. They are VERY durable..

As far as the track goes. The CAT F7 runs the narrowest easist to find track. There was a F7 EXT that ran something like a 13.5 wide 144-151 track. That would work PERFECT for your application.

I would suspect that your not planning on using this in the deep snow because Length only can give you so much floatation before the track is too narrow and just starts to trench. After 144 length id suggest going wider to at least a 15 wide track.

 

[mbsieg]

I have a bunch of 13.5 x 151 firecat tracks I will sell for very cheap they are challanger pattern with 1 in lug heighth pm me for more info

 

[NouvaNouva]

Track options =)

Thank you all for your tips. Besides width, flexibility is also a very important consideration for us to reduce rolling resistance.

Compared to the Camoplast "Ice Oval and Lemans" racing tracks are the Cobras or F7 Cat tracks noticeably more flexible? Is it correct to assume that low horsepower (<10hp) Jr. snowmobiles use more flexible tracks than the more robust and powerful adult versions?

Reducing the width of longer tracks on a table saw seems to be a much easier operation than joining two not wide but short tracks. Would it be correct to assume I could take off 3-4" off the width of both the Cobras and F7 Cat tracks?

Thanks for your input, you've all been very helpful.

William

 

[tdbaugha]

No you can't take that much off. MAYBE 3 inches. But I think 13 inch wide is going to be it. After that you are cutting into where the clips are and drive lugs that keep the track on the rails.

The Firecat track is heavier than the cobra. I do not know the weight but it is there. Plus the cobra is a single ply track verses the Firecat dual ply track. It will be easier to spin a single ply.

 

[bparks]

tracks

have you looked at the arctic cat attac 20 track you can get them up to a 162 in , single ply and very soft rubber .

 

[muskamoot]

I'd suggest you look at a Wahl brothers cleated track. They are available ib lengths from 112" to 132" and probably have the least rolling resistance of any track.The drivers are available from Wahl too. The slider center to center is less than a standard rubber track, but suspensions from common sleds can be modified to work. The steel cleats can be fitted with rubber strips if needed for operating on paved surfaces.

 

[NouvaNouva]

Mmm both of these new options seem very interesting

Thanks for those new ideas.

I really like the Wahl Bros. cleated track because it looks really flexible. It might be a bit short for our application though. I might just sound naive but those tracks seem fairly easy to make. Do you think it is a viable DIY project to make cleated tracks similar to the ones Wahl Bros Racing sells? Does any other manufacturer make similar yet longer tracks?

Are there any disadvantages to running cleated tracks? (Consider that we are running at less than 5mph and producing less than 1hp). What type of snow or ice are cleated tracks designed for?

If the Artic Cat Attack 20 tracks are as flexible as the Cobras they could be a good option due to their extra length. However I can't find them anywhere. All I can find are tracks that can "replace" them. Am I missing something? Did the manufacturer change the name of the tracks?

It looks like we'll probably go with Cobras, they seem like a solid choice. I personally really like the idea of the Wahl Bros cleated tracks but it would be better if they were at least 8" longer. Assuming same dimensions and running on snow, can we expect the Wahl bros cleated tracks to be more power efficient than standard rubber tracks like the Cobras?

Thanks everyone! Have a great week!

William

 

[muskamoot]

You could make any length track you want using cleats from Wahl bros and strips of conveyer belt material. The cleats are riveted onto the belt using solid aluminum rivets. The spacing of the cleats match the pitch of the plastic drive wheels from wahls.The cleated tracks were used for ice racing with the cleats providing a solid mounting point for studding. The tracks provided less rolling resistance that rubber tracks and were great for lower HP sleds than we race now.

 

[NouvaNouva]

DIY cleated tracks

That sounds like a really good idea! Is there any type of conveyor belt material you would recommend? A conveyor belt brand perhaps? Are there any tips or tricks related to building your own cleated tracks?

You mentioned cleats are designed to run on ice. Would they also run well in soft snow?

Thanks a lot for your help.

William