My Senior design project - a "Swamp Thing" tracked vehicle clone

[Garauld]

A quick update - recently, I did take off the teeth from the front sprockets and removed a link from the new #50 roller chains to effectively loosen the tension on the tracks. I took it out for a short spin (so as to not mess up the grass too much due to only 3" of snow) and the reduced track noise sounded promising. More evaluation/adjustment is needed. Today, I made brackets and mounted a pair of small rear side mirrors so I can view the tracks so I don't run over things. A rear-view cam & monitor may also be worth installing.

 

[trackhead]

Just ran across your thread. In my brief review, you and I have had somewhat similar trials/tribulations. I built a similar size cat recently.

Engine:Yamaha RX1 4 stroke 4 cylinder 140hp/85ft/lbs
Transmission: Stock Yamaha CVT to "chain drive differential" 4:1 reduction
Differential: Chevy 10 bolt from Suburban
Steering: Brake steering similar to yours
Weight: 2,000lbs
Tracks: 24" wide
PSI: About 0.55lbs/sq/in

Struggles:
-track noise, yup, same as you
-track pitch issues, intermittently yes, fixed to some degree with track tension
-hot brakes, yes, but they otherwise work great (UTV calipers x 2 per rotor)
-broke one axle (because I welded one up for length)
-new axles aren't welded, doubt they will break
-turning in deep snow requires a fair bit of HP and energy

Plans:
-probably convert to hydrostatic this summer, we'll see.

Nice work!

 

[Garauld]

I built a similar size cat recently...

Hi - your build looks interesting especially using a CVT drive. Do you have a blog somewhere with the build details? I didn't want to deal with the complexity and cost of using a hydraulic drive so I went with the Toyota engine.

 

[trackhead]

Hi - your build looks interesting especially using a CVT drive. Do you have a blog somewhere with the build details? I didn't want to deal with the complexity and cost of using a hydraulic drive so I went with the Toyota engine.

No blog or specific build details. The CVT was tricky getting alignment/deflection correct, but works fine so far. I ran sprocket/chain 4:1 off of the secondary clutch/shaft down to "chain drive" differential which is just a 60t sprocket taking the place of the ring gear. These configurations are used when people put motorcycle engines in small cars.

The CVT is a common Russian tracked vehicle build technique, but they often use much smaller engines. They often do engine to CVT to chain drive to automotive transmission to standard differential/axle unmodified. This makes a wider tracked vehicle because rear axle isn't cut down, but it keeps the fabrication to a minimum.

I watched your track pitch videos and noise. I chased the same damn noise on mine. Thought it was a million different things but ultimately it's occasional track noise/binding. It's hard, because you have to recruit someone to shoot video of it to diagnose it. But mine is very similar.

I'd like to 3D print a new sprocket design/mold and ultimately make polyurethane sprockets. But, a million other tweaks have taken priority.

 

[groundcover]

This is probably how the Ripsaw started out ! You guys are building a gateway tank !

Google Search

 

[trackhead]

The pioneers, in my opinion, are the Russians. I watched hundreds of videos. Those guys are building functional vehicles out of scrap. Lot to learn from them, albeit with a huge language barrier.

 

[Garauld]

I've thought about making polyurethane teeth as they are softer than the acetal I'm now using. They should be quieter if I want to go that route. Enough polyurethane stock for my 16 drive sprocket teeth (1.5" x 2" x 4") would run about $200.

 

[trackhead]

Yeah, I'm a metal on metal guy with hopes to do better in the future. I did use UHMPE teeth similar to yours but chewed them up faster than I thought.

 

[Garauld]

Hey TH - it would be great if you could start a thread in this forum and post some photos and dialog of your exploits to share with the rest of us knuckleheads!

 

[trackhead]

Hey TH - it would be great if you could start a thread in this forum and post some photos and dialog of your exploits to share with the rest of us knuckleheads!

I could but my engineering degree is all my psychotic/neuroticsm with no actual degree, and my fabrication skills are rudimentary with only the simplest of tools. Which is why I admire the Russian builds.

 

[KubotainNH]

I could but my engineering degree is all my psychotic/neuroticsm with no actual degree, and my fabrication skills are rudimentary with only the simplest of tools. Which is why I admire the Russian builds.

Please don't let that stop you from posting, most of us are just fooling around building or repairing things. Never know when someone has a good idea that can help another out. Your rig looks pretty cool and it's functional which is the main thing.

 

[trackhead]

Did your bilge pump fans remedy the hot brakes? Mine are getting too hot in some situations and I have to stop to let them cool. Might have to try your concept.

 

[Garauld]

I think the fans helped a bunch although I've not really pushed it through the paces. I think switching to the higher pressure hydraulic brake steering system makes steering more efficient and quicker. The fans were cheap and easy to install.

 

[trackhead]

Thanks. My machine turns on a dime but it’s also very light. Plowing driveways and cruising in the yard works fine, but grinding up mountains today in a couple feet and using brakes more they got soft from the heat.

 

[Garauld]

It won't turn on a dime on grass - just ask our buddy Arly!

 

[Garauld]

BTW, how are you applying pressure to the steering brake calipers? Auto master cylinders?

 

[trackhead]

Yeah blacktop and grass I won’t go near. Gravel and snow, sure.

I’m using four (two per side) UTV calipers from a Razor 1000 basically. Each has their own cylinder, so lever pushes two at a time. If the air is purged well, it’s very light lever pressure to pull and create turn.

But in deep snow that requires a lot of corrective action, they do get hot.

I ordered some bilge blowers. I’ve ran mine with the back cover off and it definitely helps.

I think real snowcats like Bombi/Imp/Spryte have brake bands in an oil bath.

 

[hayden]

Would hydraulic drive solve the braking and heat problem? Obviously you would need to cool the hydraulics. I think hydraulics are how all modern tracked machines are propelled and braked.

 

[trackhead]

Yes, but hydrostatic systems can add 3500-5000$ to build cost.

 

[Garauld]

Yes, but hydrostatic systems can add 3500-5000$ to build cost.

I don't think I spent that much to build my entire machine.