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

Garauld · May 15, 2021

I've been playing around with the LED speedometer and the hydraulic power unit (HPU) I bought to maybe use for the steering calipers. Here's a video where I am running a test of the digits and leds. The display really is not as bright as the movie but it will be enough to be seen since the large digits are 2.5" tall.

As far as the HPU goes, here's a video of a flow test and also one of a pressure test I ran. This little unit will put out 2300 psi which would be plenty for actuating the brakes, I believe. Unfortunately, as you can see in the video, there really is not any good paths for cooling air to flow thru the motor windings. In my testing, the motor got really warm way too quickly.

At this time, I have decided, at the suggestion of a fellow poster, to try and use vacuum brake boosters to increase the pressure of the brake fluid to the calipers. I have already ordered a 7" single diaphragm booster to evaluate for this purpose. I may revisit the HPU some time later or possibly use it to lift a snowblower? Stay tuned.

Garauld · May 30, 2021

I had a flat the other day in the right front tire (#R1) on the sidewall. It looks like possibly a stick got lodged in between the sidewall and the track guide angles. I just installed a tire tube - we'll see how it holds up. If I have to, I'll fill the tires with foam. I also noticed a fair amount of rubbing-inspired wear on the sidewall which probably occured when I was making turns. Short of replacing the tires, I will try to reduce the friction between the tires and the track guides by applying some grease or dry moly-lube. I wonder if the increased rubbing friction made turning harder? Got any other ideas? I recently played with my cad system and laid out a design of a vacuum booster assist for my steering brake master cylinders. It appears to fit in there under the seat quite nicely. I think I'll try installing it sometime this summer.

ArlyA · May 30, 2021

Gary knows this from my conversations with him, so this is for everyone else. Snow-cat tires have many more plys than normal tires do and are built differently for a rough life as he stated above, are commonly foam filled. The tires on tracked snow machines live hard, hard lives.

Thanks for keeping us posted Gary!

Fallon · May 31, 2021

Grease on open tracks drug through the dirt will just collect dirt. Also I bet it could cause problems as it moved around, causing slippage on your drive wheels.

ArlyA · May 31, 2021

Fallon said:
Grease on open tracks drug through the dirt will just collect dirt. Also I bet it could cause problems as it moved around, causing slippage on your drive wheels.

I agree that the grease won't work.

Garauld · May 31, 2021

I reinstalled the repaired flat tire after I sprayed the sidewalls with dry moly-lube. I also agree grease is not really a good idea. I'll spray the rest of the tires with the moly soon. FYI Fallon, the tracks are driven thru the front sprockets, not the wheels - they are all free-wheeling. Thanks for the feedback.

ArlyA · May 31, 2021

I'd say your tire guides are to square and would be hard on the side walls. The 2nd photo is what snowcat guide usually look like.

Garauld · May 31, 2021

Arly - please explain why you think they may be too harsh on the sidewalls.

ArlyA · May 31, 2021

Gary and I spoke today, so this is for everyone else. When snow machines turn, the side load stress on the tire guides goes through the roof. This is why operators hear the power plants growl when we make turns in a snow cat. Doing this puts lots of wear and tear into the idler sidewalls. This is why they do not use normal tires in snow cats but have high ply numbers and thick walled and very stiff ones. Plus the guides are very round shaped to lessen the idler damage. These photos might give you an ideals how they are built.