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Old 09-23-2018, 05:35 PM
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Default Track sled/snowdog/slowmobile help plz

Hey guys, been lurking for a while. Nice website glad to be a member, wealth of knowledge here and members!

I’m here because I’ve built a machine with my dad based solely on a YouTube video and we’ve done quite well. Machine operates pretty well and is an amazing ice fishing machine, it pulls a pile of weight and goes through considerable snow. However I’ve had a few issues and eventually made my way to this kart forum because I need some insight, please.

I’m going to upload a photo of the machine, it used to be an entire snowmobile. Here are the details.

208cc powerfist engine 3/4 shaft
Genuine Comet tav2 12tooth sprocket on driven
jackshaft in has new sprocket that I’ve got @60 teeth
Jackshaft out is original from snowmobile chaincase kept intact to retain reverse and less work for me@ 19 teeth
Finally axleshaft has a once again original from sled 35 tooth sprocket.
Axle cogs are 7” diameter that drive a track that is 121” long if that matters!
Machine weight is roughly 200lbs

I’m sure you guys now know my issues are gearing. I’m onto about 4 sprocket changes that have now gotten me as large as 60 teeth. My intention is a torque monster with low top speed to pull heavy loads through snow and across frozen lakes for ice fishing. To date I’ve pulled just north of 500lbs before I made these changes but I realized I was killing the comet and eventually burned belts. My problem now is my torque converter is still screaming hot with this latest change. Low end torque seems to die a bit after it heats up which doesn’t take long.
I believe it’s belt slip that is generating heat but I want to be sure, I can’t see it happening but I don’t know everything there is to know.
I’m hoping this pros here can shed some light as to what ratio I need to get to before the comet won’t be too hot to touch and I “shouldnt” be able to burn belts.

From my probably incorrect calculations I’m around 9:1 ratio?
Thanks in advance for the input
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Old 09-24-2018, 12:57 PM
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9.21:1 with 35T axle sprocket
and 15.79:1 with 60T axle sprocket
your calculations seem to be correct

the problem will be weight and humidity I'm afraid.

You have a serious amount of weight to carry, and the track itself is not exactly friction free itself I assume.

All that causes a serious amount of counteracting forces, which indeed eat away the belt.
especially when the sheaves start to get wet and the belt has the slightest chance of slipping.

especially with cheap belts.
So only buy original comet belts or belts of highest possible quality (MUST be series 30 Torque converter belts of course.. a V-belt won't serve you well if at all!)

I'd say you might be better off replacing the TC with a 2:1 wet clutch
it gives you almost the same torque benefit as the TC does, but without the nasty sideeffect of loosing ~20% of the motor power.
for the cost of not being able to speed up anylonger but staying fixed at that single ratio.
(i.e. cutting your top speed nearly in half)

but the wet clutches can take a lot of abuse (way more than your TC could withstand)

Next best thing is to scale up the TC,
a series 40 or even better a series 500 belt is wider than a series 30 belt and can transmit more power (and pull higher loads)
of course in order to make use of that, it means you want a series 40 or 500 TC,
finding one for a 3/4" shaft isn'trivial though I'm afraid.. sooooo yeah *shrugs*

Maybe a 390-420cc engine (with a 1" shaft) is what you need in the end to install a larger TC to fix your issues.
but that comes at the benefit of more torque a bit higher gear ratio and in the end a bit better top speed as well

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Old 09-24-2018, 02:12 PM
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40/44 series with 3/4" shaft for the engine. Expensive, but it'll be worth it https://www.gopowersports.com/40-ser...t-on-8hp-18hp/

So I'm guessing you'll just be hauling:

Ice auger
Rods
Bait
Fuel (unless your auger is a hand crank, at which point I'll say, sell it and buy a Jiffy)

So in cargo alone, anywhere from 75 to 100lbs. Are you planning on pulling a portable fish house too on the lake? If so, I'd probably get the larger engine, 40 series cvt, and gear even lower. At that point, you'll probably be around 150+ lbs of weight behind it, not accounting for sinking a bit into the snow.

You'll also want to look at re-jetting your carburetor for winter time to help out with cold starts. Actually I'd probably look at a Predator 420 or similar engine with electric start. Get a garden/lawn tractor batter ro make starting easier. Plus with the 3amp stator on it, you could add a light to it to make traveling easier at night.
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Old 09-24-2018, 04:05 PM
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Thanks so much for the reply gentlemen!

I appreciate the knowledge and recommendations.

I had a feeling I was pushing the limits on the 30 series!
To be honest I have to admit I’m a little over budget on this project and I won’t be able to do an engine and clutch change while I do agree that yes that is a solution.

In addition to budget constraints, being that a snowmobile track is only 15” wide, finding the right balance between the chaincase(which is large and full of heavy sprockets and not pictured in the photo I uploaded) and the engine placement was a tough obstacle to overcome to get the machine to track straight and not constantly lean. Also a larger engine would raise the center of gravity a bit and she is top heavy now. Uneven firm terrain isn’t easily navigated for the inexpierenced rider. Powder and a flat frozen lake on the other hand is a breeze.

I rode around on trails and in a field all last weekend on the current ratio and I couldn’t burn the belt out, I get that eventually it will but I don’t every expect to be running this machine at wide open for more than say 15-20min before the trip is over. My guess is snow will greatly reduce friction on towed loades thus reducing overall load.

As far as actual weight, my portable shack weighs 88lbs, add 20 volt drill auger, rods and gear etc it’s pushing 120 lbs. last year I towed myself and another 200lb+ adult and said shack with gear and we did fine, that was when I was running a terrible ratio but the reason that was all possible is because we were towing on hardpack snow with minimal friction.


So In conclusion and please correct me if I am wrong. Deep snow will create the most friction and I will be at my most vulnerable of overloading clutch and blowing belt and can’t expect to tow epic loads.
However if I am on hardpacked snow or glare ice as long as I can maintain traction I will continue to be able to tow considerable loads with the same results I’ve expierenced so far. Which as far as I know are eventual belt degradation.

For the future... if I can physically fit it.... is a 10tooth clutch sprocket and 72 tooth jackshaft in sprocket put me in better shape gear ratio wise? I really can’t afford another clutch lol.
Thanks guys

Edit: in regards to belt quality I do agree genuine comet belts are best however they are $45 plus tax CAD @ princess auto and I’ve recently found some on amazon for 26 and I bought one as a spare. For that kinda price difference I want to see just how much worse they are.
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Old 09-24-2018, 06:35 PM
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Weight distribution is probably more important really. The deeper the hearing you go, the less wear and tear on the cvt belt. If you have too much weight on the back of the sled hauling stuff, the more chance of it putting more strain on your vehicle.

Is your ice shack like an Eskimo or Frabil with it's own sled, or is it just one of those fold down type that you need to set in a sled?
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Old 09-25-2018, 09:47 AM
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Right,I think I’m getting picture and sound.
I think deeper gearing will be the direction I go and hope to just be sustainable which I think I will be after the real world testing and abuse really.
Yes my portable shack is a flip Style built on its own sled Eskimo Sierra to be exact.
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Old 09-25-2018, 12:08 PM
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I'm a little last to the thread and have some questions. What snowmobile chassis did you use? What modifications did you make to the suspension? I have an old Polaris that I've been wanting to use to make something similar. One problem is that snowmobiles have a slide style suspension. They have a lot of friction and drag but work very well in snow and snowmobiles have lots of horsepower to over come the suspension drag. Plus a slide suspension needs snow to lubricate and reduce friction. So if you haven't removed the slide this will be creating a lot of drag that the motor has to over come with to get it to move. By removing the slides and installing a coupe more sets of wheel would reduce the drag a lot. Look at the Snow dog snow sleds they sell. The undercarriage (I won't call it suspension because it isn't) rides on lots of wheels.
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Old 09-25-2018, 08:24 PM
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I’ve attached a photo of the machine before I made significat gear changes to show the size of the chaincase for anyone interested
Also I attached a photo of the “donor” $100 blown up 91 Polaris Indy classic. Tear down was a bit of work but what we have created so far has been worth it.

As far as the suspension goes I followed the advice of the YouTube video I found originally, not sure if links are allowed. Just search track shark, uploader is Rednic.

The skid does rely on two shocks for suspension rather than spring loaded boogie wheels. Also it has sliders that the track clips ride on and yes should be lubricated by snow. However being that all that is required for a snowmobile to operate properly I’m not 100% sold the same requirements are for a tracksled. Yes no snow adds to friction and track rolling resistance. However the suspension isn’t really a must have because no one rides on this machine it just pulls. What I have done is removed the rear shock completely. And added a steel tube cut and drilled as to express the front shock that will remain as to set the top of the tunnel level. You will notice when you tear down the sled to the tunnel and Basic front that the tunnel and track will be on an extreme lean forward. I believe this needs to be corrected to keep the front up. I’m gonna upload some before and after photos of our project #2
The difference will be obvious.
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Old 09-25-2018, 08:27 PM
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Photos of before and after suspension lock out on our second build.

Also I just wanted to mention that before I started to make gear ratio changes with sprockets this machine broke trail towing myself alone 200lbs through 1’ of fresh snow. Not powder but not soaked snow either somewhere in between and it was a blast and I was impressed. This project really has been a labour of love for me. I’m a carpenter and don’t get to play with steel and gears and mechanical stuff that often and this has been a blast to learn from and to improve on and to find out what doesn’t work 3 times before you get it right. I enjoy just rididing it around once one learns how it handles it’s fun just for that, not to mention ice fishing it’s absolutlt amazing.

The legit snowdog isn’t classified under either of our MSVA (Motorized snow vehicles act) nor our ORA(off road vehicle act) here in Ontario and therefor doesn’t require a licence or insurance or registration to operate or even a helmet. However I can tell you first hand because I’ve wiped out in the snow and a helmet is obviously a must have.
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Old 09-25-2018, 08:44 PM
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Links and videos are allowed.
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Old 09-25-2018, 08:55 PM
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https://youtu.be/MI0GVSP0fp4

My inspiration. Although I think he also has gearing issues
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Old 09-26-2018, 01:51 AM
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I really dig this thing
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Old 09-26-2018, 11:28 AM
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I've seen that video and its very helpful. One thing that baffles me is his gearing. It doesn't seem like he has low enough gearing but it sure seems like it works good? He states in the comments that he has a 10 tooth sprocket on the clutch shaft and a 16 tooth sprocket on the snowmobile jack shaft. Snowmobiles generally have 1.80-2.20 gearing in there chain case. This only gives his sled around 3.20 gear ratio. I'd think you'd need about 15 to 1 gear ratio. I don't think you want to go much faster then 15-20 mph on one of these.
These track sleds are very popular in Russia and there is a lot of build info online, but a lot of it is in Russian and doesn't translate real well. They call them Motodogs. In Wisconsin where I'm at they are popular for grooming fat bike trails in the winter time. A local club has a Snowdog brand and I got to take a good look at it. I didn't measure the sprockets but in looked like it had a lot of gear reduction. There is a fat bike forum that has a lot of info on track sleds and even a few people that built there own.
I have a 90 Polaris indy Sport 340 with a dead motor, Harbor Freight 13hp motor, and Chinese 40 series CVT in my collect for my build. Now i just need to find time to start it! LOL
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Old 09-26-2018, 03:55 PM
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Sounds like your in great shape to start a build VPD.
Yes I do believe Rednic’s gearing is way too High. My guess is with extended runtime and the clutch cover on not letting heat escape very rapidly he would also be burning belts quickly depending on conditions.

That’s where I’ve started from not knowing any better and have made the correct changes to get to a better place.
Yes the legit snowdog uses a large clutch and now I know why!
Also your are correct about top speed, these machines get scary fast in a hurry while standing and riding and learning to operate one takes a little bit. It is unlike anything else.
Also don’t bother with the thumb throttle from the snowmobile it’s way too awkward. I just changed my own to two bicycle brake levers one throttle one brake and it is one of the best things I ever did to the machine. Really allows you to have a good hold on both handle bars and allow one finger to operate levers. Keep in mind that balancing the engine with the chaincase should you decide to keep it is very important and difficult to get right. If I can save you from moving your motor 3 times like I did... lol
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Old 09-28-2018, 05:34 AM
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I have a 300lb + rider weight tracked go kart and I am basically having the same issues as you except with a beefy clutch..
It was suggested for me to go with a 30 series TC, but what's happening to you is what I fear happening to me.
I don't believe the 30 series is made to move tracked vehicles with that much rolling resistance or weight, they work fine for heavier go karts etc, but usually they roll well enough to push even a large two seater easily.
I've seen a few TC in snowmobiles and they were always much larger than a 30 series.
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Old 09-28-2018, 06:40 AM
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There's a lot of weight being moved with a small belt. They do make CVT temp gauges, mostly for ATVs and snowmobiles, but they should work in these vehicles no problem. https://www.rockymountainatvmc.com/p...lt-Temp-Sensor

Not sure what is considered normal operating temp, but should give you an idea if you need to get deeper gears or better cvt.
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Old 09-30-2018, 05:27 PM
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Quote:
Originally Posted by Slinky View Post
I have a 300lb + rider weight tracked go kart and I am basically having the same issues as you except with a beefy clutch..
It was suggested for me to go with a 30 series TC, but what's happening to you is what I fear happening to me.
I don't believe the 30 series is made to move tracked vehicles with that much rolling resistance or weight, they work fine for heavier go karts etc, but usually they roll well enough to push even a large two seater easily.
I've seen a few TC in snowmobiles and they were always much larger than a 30 series.

I think your concern is valid, Iím going to be changing my current setup to the deepest physically possible gearing I can manage while keeping my original chaincase. I believe it will put me at 15:1 and Iím confident I should have a sustainable machine. If I can get my hands on my friends thermal cam I will measure belt temp after riding for 10 min before and after gear change. Iím also going to loosen the tension on the snowmobile track and hopefully reduce some resistance there as well.
I agree with your therory about the 30 series ability to move tracked vehicles, it is asking a lot. That and all the clutches Iíve seen even in smaller snowmobiles are easily double the size of the 30 series.

Our second build is going to include a transmission that will give us reverse and we will probably use the 2:1 wet clutch over another 30 series after it was recommended to us. The new build will have a slightly smaller engine that we already have to save some $$
I would be more than happy for any input from the guys here again on the transmission mated with the 2:1, Iíll upload an photo I found online that details the transmission. At this point I have no idea what size sprockets go from the jackshaft to the axle tho.
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Old 10-01-2018, 10:24 AM
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I noticed that you built 2 of these from different snowmobiles. Do both have the same problem? I still think reducing the drag on the track and getting rid of the slide rail helix and adding another set of wheels would help reduce drag greatly.
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Old 10-01-2018, 11:24 AM
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Second machine isn’t yet close to built. I do agree that bogie wheels would be less rolling resistance as compared to hyfax sliders. However the donors I was able to get my hands on had a slider skid vs bogies. I’m fine sticking with it. I’m confident I will not have this issue on the second build after consulting with the pros here and choosing a different clutch.
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Old 10-02-2018, 08:58 AM
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I'm not saying you have to change the suspension just make a few modifications. You can take the plastic hyfax off the slide suspension and add a couple more bogie or idler wheels to reduce the friction of the slide suspension. Do some research on snowmobile grass drags. They run snowmobiles on the grass and they modify the slide suspension for less drag.
Reverse? I thought about doing exactly what your doing with the snowmobile chain case with reverse, but do you really need reverse? None of the track sleds being sold have reverse. None of the Russian homemade Motodogs have reverse. With the machine weighing in at 200lbs, do you need it? I doubt it, plus how are you going to back it up with the trailer being so short? Another thing against reverse is my sleds don't have it and when I priced the parts to put reverse on it. it was like $200-$300 for used parts. Thats way more then I paid for 2 snowmobiles! LOL
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