tracked vehicle differential questions

[SensibleNick]

Bunge cord WILL be ineffective in cold temps. I had a little plane with that setup and it goes stiff in the cold. It's rubber. But you are right, the idea is cheap and tuneable.

Open disk brakes freeze and are completely useless if bathed with snow. They must heat up, melt the snow which again freezes on the pads. I use a tracked ATV with inboard disk brakes and they do freeze if there is enough snow to fly around. You don't really need brakes though, so it is not a problem. That's why I like articulating cats instead.

Very glad to learn from your experience here Jim. I had wondered, but been unsure when it came to bungees, and the disk thing was mere speculation on my part
Coilsprings it is (for me).... :licking:

Since I last wrote here my ideas have turned towards hydrostatic drive.... negating all need for brakes

 

[SensibleNick]

... but then again... Does cold temperature affect the elasticity of a rubber band?

http://www.answerbag.com/q_view/2228701

Two nearly identical questions, two contrasting answers ....
I think I'm going to have to conduct my own tests

 

[davedj1]

I'm not terribly worried about the brakes, won't be going in that deep of snow, no worse than driving in a snowstorm.
With mostly slow speeds in the trails, I'm not sure if springs will be necessary or not.
Keep the info coming, it's nice to dream about what someday may be a reality.
thanks,
dave

 

[SensibleNick]

I'm not terribly worried about the brakes, won't be going in that deep of snow, no worse than driving in a snowstorm.
With mostly slow speeds in the trails, I'm not sure if springs will be necessary or not.
Keep the info coming, it's nice to dream about what someday may be a reality.
thanks,
dave

...If you were to chance it and go for the disks (it's what I would do in your position) you could always try that idea of routing the exhaust right up to them to keep them nice and toasty ... could even take the exhaust pipe itself though the cab and have yourself a nice hot radiator

you may be underestimating the amount of snow that'll be there though. Everything that sticks to the tracks seems to end up going around the wheels inside. Watch the videos again: the disks will be constantly showered with snow...

 

[jetboat]

have you considered using WIDE tires instead of tracks? Look at the artic trucks they use. Would make the design allot easier.

 

[jimgerken]

I'm not terribly worried about the brakes, won't be going in that deep of snow, no worse than driving in a snowstorm.
With mostly slow speeds in the trails, I'm not sure if springs will be necessary or not.
Keep the info coming, it's nice to dream about what someday may be a reality.
thanks,
dave

You don't really need brakes for stopping. I was commenting on the freezing brakes issue because I was afraid you were going to build something intending to brake-STEER, and I just know you will not have good enough brakes to steer once they get bathed in flying snow for a while. Unless you can put them well inboard where they do not get snow on them, and I am suggesting totally enclosed, with ventilation from a known dry source.
When I am out on the aTV with tracks, the brakes are inboard but open, a good foot off the ground to the lowest point on the disk, and they freeze and are worthless, and I generally don't care because the tracks add so much drag to the driveline that to stop I just stop applying power (I am pulling a rolling groomer). IF I need brakes bad enough, and plan ahead, I can ride the brakes for 100 feet to thaw them, then they are wet sounding (stiction effect) and they do work OK.
Suspension, I agree it is optional if traveling less than 15 mph in the snow, either breaking trail or running on broken or groomed trail. At that speed, you are essentially a tractor. Add an air ride or at least suspended seat if you later find it uncomfortble. Let that decision go until it proves itself to be needed, in other words.
I always wanted to build a small articulating snow cat. With tiny heated cab for one person, hitch for groomer, place for a chainsaw, etc. Still will build one if I live long enuf.

 

[MikeD74T]

....I always wanted to build a small articulating snow cat. With tiny heated cab for one person, hitch for groomer, place for a chainsaw, etc. Still will build one if I live long enuf.

Me too, but I'm beginning to think I'm on the wrong end of living long enough..... MikeD74T

 

[oughtsix]

Have you guys considered using a leaf spring or two as the "Beam" part of a walking beam suspension? The middle of the spring where the axle usually mounts would be the pivot and you could probably use the spring perch that came with the spring to help fabricate the mount. The idler wheels would then be located at each end of the spring. This would give you a little bit suspension without much hassle. You could probably even make use of the rubber spring bushings to help isolate some of the small vibrations from the cab?

Fortunately we are blessed with a wealth of wrecking yards here in the USA and leaf springs are very cheap if you ask yard attendant nicely.

How are you guys envisioning tensioning the tracks? With air filled drive tires it is a simple matter of adding / removing air. It seems you could end with a lot of unneeded complexity if you aren't careful about your design.

I have always wondered if you could find a big enough set of old agricultural floating tires if you could cut the tread off the tires and use the tread as a basis for the track?

 

[SensibleNick]

How are you guys envisioning tensioning the tracks? With air filled drive tires it is a simple matter of adding / removing air.

Bare in mind that Dave has one idea, and I've offered advice based on what *I* plan to do. 2 different projects on 2 different continents, and I reckon that he and I are about as likely to "get 'er done" as each other

My tracks will be coming from a BV202 (retired Swedish army machine, also used by the Brits I think). Their tracks are usually tensioned by sliding the rear bogey wheel back - pretty much the same as any tracked excavator.

The tracks are rubber moulded over steel cable and cleats, allowing the machines to drive on roads and into cargo aircraft without damaging them.

Drive is provided by the elevated front sprocket. In my case driven by a hydraulic wheel motor on each side. For tension I'll either move the motor mounts or shove the rear wheel back a bit, but I won't have to deal with slop or play in the tracks like a steel-shod 'dozer would.

Here's a BV202 so you get a rough idea of size of the tracks. I'd imagine Dave's machine will be bigger. (I'm only after a single set of tracks)

 

[oughtsix]

Hi,

Sorry to drop in on the thread. I enjoyed the videos that were posted a few pages back... some really cool vehicles there. That swamptrax thing was just amazing.

I realize that there are a couple different projects in this thread but it seems like there are some common problems to overcome... and I really enjoy pondering such things.

Are you going to be able to get the tensioning bogie wheel off of the machine you are going to get the Tracks off of? I certainly would if it were available! If a ready made solution isn't easily scavengeable it seems like it might present a considerable engineering issue.

Personally I like the hydrostatic solution. I even have a brand new dual hydrostatic skid steer pump in my shop and several wheel motors and a couple torque hubs for a wheeled project that is moving VERY slow. All were some great ebay scores over many years but the hydraulic stuff can be very costly!!! I haven't even started looking at hydraulic lines and fittings for my project yet. Once you start adding all of the hydraulics up I can certainly see the cost advantage to a differential and independent brakes.

I am currently banging my head on the easiest way to couple my dual variable pumps to a 1.6l toyota engine without loosing the starter mount.