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

[Garauld]

Willy - I looked at a bunch of pricey options and I had a bunch of free hardwood I could use to make wheels. They are all installed and I took Snowzer out for a ride and they appeared to work just fine. What additional support are you suggesting that steel sides would provide? FWIW, each wheel normally supports about 500 lb.

 

[airbiscuit]

Too bad you can't get air bags for your suspension.

 

[KubotainNH]

Would it be possible to do something simpler like a leaf spring centered upside down with the ends pushing down on the pivoting arm? Like the old school front suspension on a Ford Model A.

 

[Garauld]

I wouldn't think there's be enough room for leaf springs under there. Thanks for the feedback!

 

[Garauld]

I've been playing around with designing an electro-hydraulic pressure control system for the brake steering. Instead of using a master cylinder for each rotor, I thought a small hydraulic pump could be used to increase the net pressure at the calipers. I set up a small test system (yes, that is a HF 12v drill motor) a while back and was able to see 3600 psi on my 4000# pressure gauge (see first photo). When I checked into the availability of another pump kit, I found they were no longer available. I bought another small pump and will be testing it out soon once I plumb it up (2nd image). The third image shows what a dual pump setup may look like. I envision using a roller chain setup connected to each steering arm to rotate a ball valve to control the pressure. Will it work?

 

[Garauld]

I ran the test hydraulic setup today and got over 3600 psi out of it. The poor little HF drill motor was not happy at all and was very noisy. I may buy a used 12v Dewalt drill and try it instead as I'll bet it has a bit more power and would last longer.

 

[Richard001]

You might want to check to see how much pressure the brake calipers will take. I don't think that they are design for such high pressure.

 

[Garauld]

I don't think that they are design for such high pressure.

You may be right and plan B would be to use lower pressure of say 2000 psi and use the two service calipers for additional steering friction. The service brake would then move to a new rotor and caliper mounted to the input of the front diff. I looked at calipers used on Audis and VWs that incorporate a manual parking brake lever which may be a useful feature. I think I covered this in an earlier post.

 

[MTGreen]

How are your wooden wheels working out?

 

[Garauld]

Due to a lack of snow here, I have only tried them out a little bit so it's too early to tell.

 

[KubotainNH]

I looked at calipers used on Audis and VWs that incorporate a manual parking brake lever which may be a useful feature.

Some Fords and Hondas also have these. May be cheaper than VW but maybe not.

Mustang example.

 

[Garauld]

Thanks for the tip. I was not aware of them used on Mustangs.

 

[Garauld]

Just a quick update to some of the enhancements I've chatted about earlier. I've been performing some major surgery on Snowzer with most everything associated with the tracks removed. In summary, a) I plan to add chain drive to power the rear track sprockets from the front ones (image 1). Most of the parts are made and I am about to install some of them. I still need to pull off the the front drive sprockets, hubs and half shafts which will need to be shortened. B) I will be adding springs to the walking beams that support the track wheels (image 2). This will hopefully provide softer action and reduce the hard banging that currently occurs when a wheel encounters a bump and then the walking beam hits the hard stop. C) I am going to install electro-hydraulic pumps that will be used to pressurize the brake calipers used for steering. Image 3 shows how I might install the system. I initially plan to be able to send as much as 2000 psi to the calipers to see how it steers on grass and can bump that up to 3500 if necessary if the calipers can take it.

 

[airbiscuit]

You could learn a thing or two from this guy

 

[Garauld]

I checked out his Youtube feed but did not see any details on how he built it. Did he use snowmobile tracks? I admit - he has built some neat projects over the years.

 

[Garauld]

A quick update on my latest Snowzer efforts. The rear sprocket drive chains have been installed and I am in process of wiring up the hydraulic pump system for steering. I am also making up a new set of wooden wheels that will have replaceable UHMWPE pucks to push against the track guides. Pics will be added shortly.

 

[ArlyA]

You could learn a thing or two from this guy

Its a trackster, likely a more modern one built in Montreal WI. Not the dated one see here.

 

[Garauld]

Since my last post, I finished up and installed the new set of four wooden support wheels with the UHMWPE side pads (see pic). The wheels came out so nice I ordered more UHMWPE to affix to the remaining wooden wheels.



I also completed installing and testing the hydraulic steering system and tested it. I attached a short movie showing it's action. I think 3000 psi is sufficient and the responsiveness looks great. I will be test driving it soon.

https://imgur.com/iVmmDHu

 

[Garauld]

I finally have all eight support wheels changed out from inflatable trailer tires to solid wood wheels with UHMWPE side thrust pads. You may notice some are missing screws on the pads which I plan to install once the rest of my order is delivered. Note how nice they will be guiding the tracks when turning where the tires were having issues. As you can see, I have it up on my maintenance ramps so I can crawl underneath comfortably.

 

[Garauld]

We finally had enough snow here recently to where I thought I could take Snowzer out for a spin around the yard without tearing up the lawn too much (gotta keep the wife happy!). I found that the new hydraulic steering system (HSS) seemed to work quite well and I will continue to evaluate it. I also noticed that the tracks were much noisier than before when I added chain drive to the rear sprockets. It sounds a lot like the teeth on the front sprockets, which I left installed, are being excessively impacted by the track grousers. I will be removing them when weather conditions improve. Happy holidays everyone!