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

[ArlyA]

I think your sprockets are slipping because the belt has too much stretch in it. I also think you should make an extra pair of sprockets for each side that helps keep the belt round instead of it going flat between the cross bars as it goes around the sprocket. The pitch between the bars of the belt is changing because the force on the belt is pulling the belt flat between the teeth as it goes around the sprocket. This results in the bar on the belt hitting the tooth half ways up the profile of the sprocket instead of at the root of the tooth where it should be. The noise you hear is the bar on the belt slapping against the sprocket as it slips down the tooth into place. Your drawings show the belt as following the curve of the sprocket but I'm thinking if you watch a video of the rear sprocket you'll see what I mean.

If Garauld already has than much belt stretch,,,, he's got lots of design grief happening. Seems the profile of the cog teeth is not appropriate and he needs to up his belt tension some.

 

[Garauld]

I see the teeth on the Bombi are designed so there is no metal to metal contact. If need be, I plan to wrap the steel wheel spools with a thin (1/16" or so) strip of UHMW to quiet it. Arly, do you think it would work? The other plan would be to make the teeth all-encompassing like the ones on the Bombi.

 

[Mat4644]

Wow - what a project!

 

[ArlyA]

All modern cog drives as far as I know, are made from HPDE of various types. Here is a few photos. Adding plastic to make a less noise, I'd guess would help.

 

[Garauld]

I milled up another set of 16 drive sprocket teeth today - ain't they purty?

 

[ArlyA]

I milled up another set of 16 drive sprocket teeth today - ain't they purty?

View attachment 664824

Yes indeed that are nice. :thumbsup: Do wish I could do nice mill work like that.

 

[Garauld]

I got the service brake working pretty well today. I previously installed a master cylinder (MC) that originally came off a Kawasaki m/c. It had a 1/2" bore and about a 1/2" stroke. As it turned out, I could see the brake pads on both calipers move a bit and then the MC would hit it's end of travel. I swapped it out with a clutch MC from a Toyota - it has a 5/8" bore and a 1-1/4" stroke. I made a shorter and fatter reservoir for it and it worked out just fine. I now wish the UHMW plastic would show up for the upper track supports.

 

[Happy Gilmore]

Awesome job, been enjoying following your progress!

 

[Garauld]

Hi - I have been dodging rain storms here trying to get some items done. I finished adding the new taller sprocket teeth and longer track support rails (in white). A test run went well with no tracks slipping the teeth. There's still a bit of chatter that I need to look into. I also added the logo to the front face panel.

 

[Garauld]

I think I am going to ditch the hydraulic track tensioners. Functionally, they work well and easily tension the tracks. In spite of installing leakproof zerk fittings, the grease I use in the rams still seems to find a way out, probably past the threads. I am using crush washers too. This causes the belts to lose their tension. I have a design made up using 1" all-thread that, when tightened, will push against the rear track idler spools.