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

[Kyle_in_Tex]

Interesting. Count me in to watch.

And welcome to TractorbyNet!!!

 

[TMGT]

See if you can add a governer to the engine and limit the rpm, that'll reduce peak power.

Also I would gear it for a top speed with the engine turning about 3-3500rpm or so, 6k is screaming and unnecessary with that power to weight. It'll just be annoying and cost you fuel.

 

[Garauld]

Hi - the Echo and Yaris models are essentially the same but were offered in different markets according to Wikipedia. The idea of a governor or rev limiter may be pursued. The real reason why I wanted to detune it was I am a bit nervous about the torque on the drive components due to the double differential reduction. My search for a suitable compact differential having a tall gear ratio brought me to the Rav4 line. The newer Rav4s have a taller ratio of 2.28 which would have given a bit faster vehicle speed and lowered the torque to the drive axles. They, however, have some funky electric clutch on the input shaft which I wasn't sure would work out. The one I bought was available and only cost $100. Keep in mind, the stock axles, which are probably heat treated for strength, will need to be cut and shortened. I hope I can make them strong enough for the potential torque loads. There should be enough room under the cab to add a reversed transfer case to gear the speed back up but for now, I just want to see it run before adding bling. FWIW, I did not find any reference to another design using a fwd engine and locking one of the axles so I hope this works out.

 

[Kyle_in_Tex]

Have you thought about what tracks you will use?

 

[airbiscuit]

From Farm Show Magazine ....

Home-Built Rubber Tracked Crawler

"It'll push snow like you wouldn't believe," says 82-year-old Ranford Adamson, Carman, Man., about the 4-WD crawler tractor he built using a 50 hp gas engine, a pair of Chevy Vega rear axles, and a 3-speed truck transmission.
"It's as big as a D-4 Caterpillar and will crawl over almost anything," says Adamson, who used 18.4 by 38 rear tractor tires to make rubber tracks for the tractor. The tracks have 7 1/2 ft. of surface contact with the ground and ride on 4 pairs of dual wheels on each side for a total of 16. The front and rear dual wheels on each side are 13-in. car tires and the center wheels are smaller.

A home-built 6-ft. wide dozer blade mounts on front.
"I've been building things ever since I was 12 years old," says Adamson, a former blacksmith who retired 17 years ago. "It works beautiful and is built so well that most people who see it can hardly believe that I built it. I built it all out of my head without using any blueprints. I use it to grade gravel and dirt and to move snow in the winter. The 4-WD keeps it straight -- even when the blade is at an angle it won't pull sideways if it hits something. Also, it rides nice without the jarring up and down motion you get with steel tracks. In fact, it rides better than my 1993 Dodge Dakota 4-WD pickup.
"I spent about a fraction of what new D4 Caterpillar sells for to build it. I bought some new steel but was able to salvage a lot of used stuff. I bought the 50 hp gas Waukesha engine from a friend. I got the tires cheap at a junkyard."
Adamson used 2 by 4 rectangular steel tubing to build the main frame and 3 by 2-in. steel tubing to build a separate frame at the rear that slides into the main frame and bolts onto it. The seat and gas tank are part of the rear-mounted frame. He welded U-clamps and a nut onto the rear axle and uses a pair of 20-in. long, 1-in. dia. threaded bolts to move the rear frame forward or back to tighten the tracks.
He made the tracks by cutting the sidewalls off each tire, leaving a 4-in. lip on both sides. To mount the tracks, he moves the rear frame up and jacks up one side of the tractor. To hold the tracks in place a row of 3-in. long steel guides inside of each track runs between the dual wheels. The guides are bolted to the track every 6 in.
The 4-cyl. engine is connected to a 3-speed transmission off a 1974 International truck. The transmission chain-drives a jackshaft which in turn chain-drives the driveshaft off a 3-ton Chevy truck that runs between the two drive axles.
"The engine has a lot of power," says Adamson. "It maxes out at 1,375 rpm's and idles at 375 rpm's so it's easy on fuel. It's the same engine used on old United Allis Chalmers tractors. I used 1/4-in. plate steel off a hot water boiler to build the blade. I can angle it up to 45 degrees in both directions by changing the position of a pin on either side of the blade's mounting system. The tractor has live hydraulics. I used the pulley and drive system off a 55 Deere combine and run the pulley directly off the engine crankshaft."

FARM SHOW Magazine - Latest Farming & Agriculture News, Farm Shop Inventions, Ranching & Farming Tips, Time-saving Tricks & the Best Farm Shop Hacks, DIY Farm Projects, Barn Hacks, Boost your farm income, time-saving farming tips, farm and Ag equipme

 

[MossRoad]

Hi - the Echo and Yaris models are essentially the same but were offered in different markets according to Wikipedia. The idea of a governor or rev limiter may be pursued. The real reason why I wanted to detune it was I am a bit nervous about the torque on the drive components due to the double differential reduction. My search for a suitable compact differential having a tall gear ratio brought me to the Rav4 line. The newer Rav4s have a taller ratio of 2.28 which would have given a bit faster vehicle speed and lowered the torque to the drive axles. They, however, have some funky electric clutch on the input shaft which I wasn't sure would work out. The one I bought was available and only cost $100. Keep in mind, the stock axles, which are probably heat treated for strength, will need to be cut and shortened. I hope I can make them strong enough for the potential torque loads. There should be enough room under the cab to add a reversed transfer case to gear the speed back up but for now, I just want to see it run before adding bling. FWIW, I did not find any reference to another design using a fwd engine and locking one of the axles so I hope this works out.

I think there's some mention of that on some 4x4 forums where folks take transverse engine, turn them 90 degrees, and use the driver's side shaft to run a transfer case to turn both axles. Keep searching.

 

[airbiscuit]

 

[Garauld]

I plan to build each 14" wide track up from two 5" wide x 1/4" thick pieces of conveyor belting. The 4" gap in the center is where the 4" sprocket teeth will pass. A piece of 1" x 1/8" channel made from a 14" piece of 1" x 2" x 1/8" rectangular tubing (which will be plasma cut in half) will be bolted to the belting. Angled tire guides will keep the 4" wide LT trailer tires centered.

 

[aczlan]

This engine has an open differential which will allow me to lock the axle pointing aft by bolting it to the frame. The forward axle will then be connected to the drive differential up front for driving the tracks.

I would HIGHLY recommend that you weld up the differential rather than bolting one side to the frame.
The spiders gears in the differential are not intended to have one side spinning and the other side not moving the time. Affixing one side to the frame and leaving the other side to spin will cause the spinning side to spin at double the "normal" speed for a given gear and engine RPM.

Aaron Z

 

[Garauld]

I would HIGHLY recommend that you weld up the differential...

I don't disagree with that. I just wonder if getting into the diff would be worth the effort. I have a factory manual here - I will look into it. Thanks for the comment. Since you are only a hop, skip & jump from me, may be you could help me?