Looking for info on MAX running gear for a project

[mpilihp]

Hello I am new to 6x6s and I am interested in them to build a snowmobile trail grooming machine. I want to model it after the ASV Tracked truck, just a smaller version starting with a Subaru mini truck. The ASV has wheels or skiis up front and tracks in the back that have independent power to each track to assist in turning.

I was originally trying to do with snowmobile tracks and skids but to figure out the mechanics to individually control power to the tracks was too much for me. Thats when I got the idea of a 6x6. So I have some questions about the running gear I am hoping someone here can help me out with, my questions will focus around the MAX 6x6 as that seams to be the rig that comes up for sale around me the most (Maine).

I would want the engine to be in the front so it is behind the cab of the truck.
- Are the forward and reverse gears in the t-20 the same? If not can I simply rotate the tranny so the running gear can be put in backwards?

- How much power can a T-20 tranny handle? I am expecting to put a larger engine in it. A Ski doo Skandic with a 550cc two stroke engine works very hard to pull a drag and that has 50hp, so thinking will need more, I was thinking of a Yamaha Phazer 500cc 4-stroke, it generates 80 hp.

- Reading on your site I see there are different running gear setups in the MAX units over the years, what is the min year to get the #50 chain setup?

- How does the T-20 work? It sounds like there is a fwd/rev shift lever along with the control levers? Once in gear, how does the clutching work in regards to the engine throttle?

IE if the engine is at idle and you push the levers forward does the vehicle move forward slowly? Or can you have forward engaged with the engine idling it will sit still until the engine rpm is raised?

My thought is primary steering would be with the front wheels/skis but when a sharper turn is needed I could disengage one side wheels(will have tracks on back too). So I would have a setup where I could lock both transmission levers in either forward or reverse for normal operation and then disengage one side as needed to turn sharper.

I look forward to your input.

Thank You ~ Phil

[dirtdobber]

Hi Phil, I can help you some:

- Are the forward and reverse gears in the t-20 the same? If not can I simply rotate the tranny so the running gear can be put in backwards?
I'm not sure what you are asking. Forward and reverse is the same ratio and the source of power output from the transmission is the same for both directions.

- How does the T-20 work? It sounds like there is a fwd/rev shift lever along with the control levers? Once in gear, how does the clutching work in regards to the engine throttle?
There is a gear selection lever for forward, neutral and reverse. The control levers are connected to braking bands inside the transmission. Depending on the gear you have selected, applying force to the steering levers activates one set of bands in the transmission and ultimately produces power to the output sprocket. Moving the lever in the opposite direction activates the opposite band and creates a braking action on the output shaft. Thus, moving one steering lever forward and the other back delivers power to one set of wheels while the other set is locked by the braking action. This makes it turn.

The T-20 is basically 2 transmissions in one. If you have seen the term "split shift", it means each side of the transmission (F/N/R) is controlled by separate levers. This allows each set of wheels to move in opposite directions for tighter turns.

The clutching is a continuously variable system. There is a pulley attached to the engine (drive clutch) and at idle the pulley sheaves are far apart and do not grip the belt. As RPM's increase, centrifugal force closes the pulley sheaves and they grab the belt and transfer power to the T-20. As the RPM's continue to increase, the sheaves close even more and "squeeze" the belt to run along a larger diameter, all the while the diameter on the T-20 pulley is reducing. This continuously changing diameter of the drive and driven pulleys produces a low ratio, high torque situation at lower speeds, and a higher ratio, lower torque situation at high speeds.

IE if the engine is at idle and you push the levers forward does the vehicle move forward slowly? Or can you have forward engaged with the engine idling it will sit still until the engine rpm is raised? If everything is adjusted properly it should sit still at idle even with the levers pushed forward and the gear selector set to forward. Of course, the same is true for reverse.

My thought is primary steering would be with the front wheels/skis but when a sharper turn is needed I could disengage one side wheels(will have tracks on back too). So I would have a setup where I could lock both transmission levers in either forward or reverse for normal operation and then disengage one side as needed to turn sharper.

I have no experience with snow, but I suggest you account for a system to disengage one side of the drive wheels in order to make easier turns with the skis. This is as easy as releasing one lever or the other. Otherwise your turns may be difficult as you will be trying to turn with "positive traction"

[mpilihp]

Hi thanks for the information, so it sounds like it will do what I'm looking for. So on your last comment I intend to be able to lock both levers in either forward or reverse for going forward and slight turns as I would mainly have my hands on the steering wheel. But in tight turns Ill use one hand on the lever of the inside set of wheels to lessen the power to those wheels to assist in turning. Sounds plausible.

THe other concern is having the chains and gears exposed, Ill have a 'chain guard" to protect it from bottoming out on something but it will not be in a tub and 'dry' IM sure it would be fine in the winter but if I take the tracks off and run it in the summer I am thinking it will get dirty and shorten the life of the chains and sprockets.

How long do chains and sprockets typically last?

So how much should I expect to pay for a run down Max 2??

THanks

~ Phli

[dirtdobber]

How long do chains and sprockets typically last?

There is no hard and fast rule on this. Lots of factors impact lifespan such as quality of the chain and sprocket, operating conditions, maintenance, stress load, etc.

So how much should I expect to pay for a run down Max 2??

I've never owned a Max machine, but they seem to vary widely. You can get an idea by searching Craigslist and Ebay and see what people are asking.

[john swenson]

hey phil...if i understand correctly, your design of the machine is with 2 tracks in the rear ( right side..left side ) driven by the t20 like in our aatv's and then 2 skis on the front ? if the front skis could pivot laterally and each one had a small fin underneath towards the rear, when you pulled back on the t 20 levers and went into your turn, would'nt the skis turn automatically without the need of a steering wheel ? like a zero turn mower. johnboy va.

[mpilihp]

Hi John I intend to steer with the front wheels/skis as the primary turning control and then only activate or rather deactivate power to the track on the inside of the turn when needed. Reading about different AATVs on this site I like the sound of the ox unit that is hydro powered like a bobcat but Ive never seen one for sale before. I have seen Tracksters but those are boogie wheel based and not soft tire based which I want to go soft tires to be able to run it in the summer too without the tracks.

[john swenson]

phil, punch in '' early tracked autos with skis ''..........johnboy va.

[wedge]

If your not intending to use skid steering and steer with the front you don't need a T20 trans. All you need is a Limited slip dif in the rear. Would be Cheaper and less work !

[liflod]

Sounds like the drive train from my Alsport Tracker. The steering mechanism will disengage the inside track when turning. It also has dual foot brakes to brake the inside track in a turn.

[mpilihp]

If your not intending to use skid steering and steer with the front you don't need a T20 trans. All you need is a Limited slip dif in the rear. Would be Cheaper and less work !

So are you saying with a limited slip diff I could do what the guy on this site did with the VW power 8x8 and apply a brake to the inside track to slow it down and assist in turning? IE what Liflod is saying in the post below??

I would then need to build from scratch the entire drive line which probably would be cheaper but harder for me. Are drive shafts/hubs and so on readily available?