Tracked vehicle torsion bar axle design alterations.

toyrocs · Mar 1, 2017

I'm rebuilding a snowcat ( thiokol) with the oem torsion axles. I was thinking of removing the center axle(s) 12" wheels. Installing a walking beam on the torsion axle(s) shafts, then install 2 new smaller wheels.

This should provide a better ride over rough surfaces.
Other pros/cons like : wheel/ axle failure, easier to detrack, tract tension variations?

Any input/ suggestions on this redesign will be appreciated.
Thanks.

Snowy Rivers · Mar 1, 2017

Not a bad concept.

My worry would be with the smaller wheels not supporting the top span of the track, which will result in a lot of sag.

Depending on the width of the track this could be an issue.

Which machine ??? Imp, Spryte ???

Adding carrier wheels on top would stop the issue of track sag.

Overall, the original design is a good balance of stability, ride quality and dependable function.

Does your machine have a blade up front ??
What engine ??

The original torsion axles were not a bad design, but there are alternatives.

Flexiride makes a sweet setup of either full axles or half axle sets that are available in various weight ratings.

The front axle on most machines, especially if it has a blade have a higher weight capacity to carry the blade.

The center axles are softer to give a decent (Subjective term) ride quality.

Another thing to consider is the condition of the rubber torsion sections of your axles.

How old is the machine ??

The rubber units degrade over time as well as the quality of the ride goes south too.

New complete factory axles are not cheap and if one side fails it is a fresh axle to fix it.

Several folks have retrofitted the aftermarket Flexiride units or others to replace worn out factory axles.

Derailing tracks is always a worry and when you change things in the undercarriage away from original. There is always a possibility of issues with a tracked rig, butttttttttttttttt ?????

Personally I don't think the walking beam is going to really do much for the seat of the pants feel.

On anything but soft fluffy fresh snow these rigs are not a Cadillac by any means.

More info on your rig may help answer things, and others will no doubt chime in.

toyrocs · Mar 1, 2017

Snowyrivers thanks for the reply.

Project details: Original machine : mid 70s (?) 2100c Thiokol Packmaster with 391 ford and C6 transmission. Oc-12 .
Proposed changes / mods: narrow the width to 102" ( for transportion issues). Severely lighten vehicle------ have already removed the engine/ transmission/ drive line brake.
Purchased a 2014 GM LV3 ecotec3 all aluminum V6 (4300cc) engine with the mated GM 6L80e transmission. Drive shaft brake/drive shaft already designed. New V6 engine to be located midship. All of the front structure to be cut off where the ford engine was mounted.
New light weight cab to be designed/ built to seat 6 people.

Intended use is to occasional plow small sections of trail/ road that are impassable, due to drifts forming extreme off camber( side hills). Also snow camping/ expedition type use over extreme terrain ( snow covered rock/ boulder 4x4 trails).

wannagoflying · Mar 1, 2017

Toyrocs sounds like a major overhaul of under carriage. What is intension of shorting drive axles. Do you have gear reduction? Photos please

Snowy Rivers · Mar 1, 2017

Sounds good.

Once you get the huge weight of the big FOMOCO V8 off the chassis, things should actually be smoother as far as the ride goes.

PICCY'S we want piccy's :w00t2:

toyrocs · Mar 1, 2017

wannagoflying said:
Toyrocs sounds like a major overhaul of under carriage. What is intension of shorting drive axles. Do you have gear reduction? Photos please

The Oc-12 has the 6.14 R&P with the 1.83 drop box gears I bought from snow cat Pat.

For the reduced width drive axles. The plan is to cut and shorten/ reweld the axle tubes and shorten and respline the OEM axle shafts to match.

toyrocs · Mar 1, 2017

Snowy Rivers said:
Sounds good.

PICCY'S we want piccy's

I just Knew it!!!!! I could not get away without a pic request(s).. From you guys.

I have been reluctant to post project details/ pictures here or anywhere! Right now no pics just a 2100c in many parts and a new V6 engine and transmission( 90 total miles) on a pallet. I'm not a talker--- more of a doer if ya know what I mean?

toyrocs · Mar 1, 2017

As for the visual eye candy requests, I do plan to do a project report at some point once the major design features/ specs are defined then frozen. I might post up a couple pics in the next month or so. I,m traveling / training out of state this month.

Snowtrac Nome · Mar 1, 2017

here is an idea I was tossing up as my 2100 rides like crap to I was thinking of relocating axles, and attaching walking beams to the axles with stub axles at each end of the walking beam allowing me to use the same road wheels

toyrocs · Mar 1, 2017

relocating axles said:
Don, what your suggesting is very similar to what I was thinking. There would be a huge increase of leverage on the OEM stub axle. I think one would have go way up on size of the OEM axle diameters/ bearing sizes. Heck it could even be large bushings.

Putting 2 oem wheels on the one OEM torsion arm/ walking beam, I think may double the load on the axle under some circumstances. Something to consider anyway.

Alaska Snow Cat · Mar 2, 2017

The Br400+ uses a walking beam but still has a "normal" bogie wheel arrangement. I have no personal knowledge on how well it works but the brochure I have somewhere shows it. Rear two wheels for sure are on a walking beam and possibly the next two wheels going forward.

Snowy Rivers · Mar 2, 2017

I was thinking about using a custom trailing link with an air bag on each one to give an adjustable ride.

After discovering the Flexiride axle system I decided to go that way.

Sadly though I really think that these cats are just not going to ride like a cloud no matter what we do.

The nature of the suspension geometry is such that it is going to be a tad stiff.

Now... I thought

With your mid engine mount design, possibly doing an air ride on the front axle might take some of the jolt out.

My Van cat (Franken Cat) is going to retain the front torsion bar suspension on the van and the spindles will be the anchor point to the cat frame.

This will give a tad extra "cush" under the front end and hopefully the passengers too.

Getting as much cushion under the front is going to do the most for your ride quality.

Keep us posted on things.

Sounds interesting.

Snowtrac Nome · Mar 2, 2017

toyrocs said:
Don, what your suggesting is very similar to what I was thinking. There would be a huge increase of leverage on the OEM stub axle. I think one would have go way up on size of the OEM axle diameters/ bearing sizes. Heck it could even be large bushings.

Putting 2 oem wheels on the one OEM torsion arm/ walking beam, I think may double the load on the axle under some circumstances. Something to consider anyway.

I can safely say this from experience the oem bearings will fail before the spindle will I have broke out several also with a walking beam there will be a lot less stress just because there will mever be the whole weight on the machine on that one axle

topwelder44 · Mar 2, 2017

iam not sure if it was on this site or some where else ----but there is a story about why the packmaster was built the way it was it even had drawings showing center of gravity and pivot points----I ran a packmaster for a lot of years we had the ford 6 cyl. in it. maybe your smaller lighter motor up where it goes might change the ride---are cat rode fine--any 2 track cat is going to have spots where the nose comes crashing down and spills your beer----my sv 200 rides along pretty nice but I get nose crash from time to time---I had a sv252 that I really didn't care for its ride---alittle bigger and more weight same running gear---it even turned harder than my sv200----my geo tracker on mattracks never spills my beer lol----maybe someone on here knows where that story is

topwelder44 · Mar 2, 2017

moving that motor back could make the nose crash down even harder----with the weight in the back -------------will hold that nose up longer-----?

toyrocs · Mar 2, 2017

topwelder44 said:
moving that motor back could make the nose crash down even harder----with the weight in the back -------------will hold that nose up longer-----?

Thanks for the concern. I do plan to install a 6 way plow on the front ( aprox weight. 350- 400 lbs). So the weight transfer may not be as much as you imagine.

Snowtrac Nome · Mar 2, 2017

the real concern withy the 2100, is the lack of clearance on the rear driver, and no suspension when you start up a hill you will feel that rear sprocket hit the ground also ran it over buried rocks in the past.

Snowy Rivers · Mar 3, 2017

I agree 100% with Welder and Snowtrac

I have never driven the 2100, only Spryte's
Here is the graph Welder spoke of...

The center cab is similar in ride to what you get in an airliner by getting a wing seat vs a tail or nose seat.

Best ride in the middle

I do fully understand the "Nose crash"
A day on a trail full of nasty moguls and wind drifts can be brutal.

Alaska Snow Cat · Mar 3, 2017

Having a blade mounted on the front and carrying a load of snow makes a big difference in the stability of a cat.

toyrocs · Mar 8, 2017

Snowy Rivers said:
I was thinking about using a custom trailing link with an air bag on each one to give an adjustable ride.

Sadly though I really think that these cats are just not going to ride like a cloud no matter what we do.

The nature of the suspension geometry is such that it is going to be a tad stiff.

My Van cat (Franken Cat) is going to retain the front torsion bar suspension on the van and the spindles will be the anchor point to the cat frame.

This will give a tad extra "cush" under the front end and hopefully the passengers too.

Getting as much cushion under the front is going to do the most for your ride quality.

Snowy rivers,

I agree with you. The nature of the OEM suspension geometry is the problem and is a compromise like all designs will be.

My #1 attribute is to keep the TRACKS ON!!!!! I travel many times in the outback by myself and MUST have a very reliable rig!

I am thinking of making NO changes to the OEM track design, but using air-ride seats to help cushion the ride some. This will also shorten my build time!

Or alternately design/ build a suspended cab like some of the Big Rig on road trucks ( cab suspended on airbags).

Thoughts?

Tracked vehicle torsion bar axle design alterations.

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