perfect build?

[quintonhall]

I have owned different offroad vehicles in quest of unstoppable vehicle for the swamps, woods and water of Florida. And have researched many more types. What I feel like would work well is a relatively light weight amphibious with good ground clearance and traction for mud. Of course reliability is important and costs to build two machines also. After all, who are you going to call when no factory built machine can reach you? Skid steer would allow building a more narrow machine since no clearance is needed for tires to angle in for steering as well as tighter turning. I'm thinking a t20 trans driving 6 44" tires. The tires would give clearance and flotation as well as suspension. Also when you climb over a object the taller ratio would allow easier climbing and reduced need for traction. Instead of a tub in would have a tube chassis frame like a buggy. Overall width would be no more than 6'. Length would most likely be around 8'. Center of gravity would be kept as close to center line of tires as possible. The front and rear axles would be mounted as far to each end as possible, giving greater approach and departure angles. Top speed not important, would want much speed in bad terrain. 25-35mph max would be plenty in open areas. Wheel speed to clean out tires not a desire either, when you spin in swamp muck ( mixture of silt and vegetation, smells bad) it only gets worse. I would think about 30hp would work fine and I understand that t20s are fine and even higher hp levels. Offroad truck tires are designed to work with higher wheel spin so the tread would not work well. My thoughts are to use worn out tires and bolt cleats like on tracks through tires. This would give good traction at lower wheel speeds and also allow easier turning. Bolts would be sealed and tires would still be plenty strong. The cleats would be much lighter than a new tire with thick rubber tread. Any thoughts on this?

[Stonewall]

The first thing that I see is running 44" tires with a T-20. Sure, the T-20 can take 100 HP, but 100 HP isn't what turns those tires. You need TORQUE, and I think that the amount of torque required to turn, much less skid steer, those size tires will destroy the small internal parts of the T-20. Our largest tractor has 7 foot diameter tires, but is only rated at 425 HP. There are muscle cars that rate over 1000+ HP, but there's no way that they are going to turn 7' tires. This is because the tractor generates HUGE amounts of torque. I have been throwing around some ideas for a similar tracked vehicle that will be larger that what you want, but could easily be scaled down. My thread is here: http://www.6x6world.com/forums/other...s-mud-hog.html

[chris davison]

Mud hog is right. To get the torque you need you would have to put 30 inch diameter sprockets on the axles there goes your ground clearence. Anybody know off hand what the max torque is for the t20? I kinda like the gaganators build but i think I would have used the rearends with the housing still on them and put a sprocket right on the pinion yoke for the drive shaft and run a 1.5 inch shaft from front to rear
driven off the trans output shaft. you could get more gear reduction from that setup and run bigger tires with suspention.

[mudbug3]

quintonhall



The forum member BW6 built a 6x6 that had an all aluminum tub,31 hp Briggs motor,T-20, and 30 inch Mudlite atv tires on it. The 30 inch tires put some much torque on the T-20 that it twisted the splines on the 1.25" jack shaft.

[chris davison]

Bw6 what were your axle diameters and sprocket sizes for those 30 inch tires?

[Bw6]

Chris, if I remember I had 11T on the T-20 to 27T on the jackshaft, then 16T to 18T down to the 1.25" splined axles. All #60HD chain. The axles were stock Argo 1.25" I sheared 2 axles, and twisted the splines on the 1.25" jack shaft like a barbers pole. Can't count the number of times I broke the chains. Also had a 3.4:1 ratio on the CVT. Also I believe that the T-20 has around a 5:1 internal reduction via the planetary/sun gears as well. It wasn't until I divided the power between the front and middle axles before the damage stopped. Also I went to 4340 HTSR (heat treated/stress relieved) for the jack shafts, to stop the splines from twisting.

Those 30" ITP XXL Mudlites are very aggressive tires and definately not meant for skid steering. I had plenty of torque, (twisting 1.25" spline jackshafts), and pulling #60HD connector links apart. BWII could idle it's way up very steep hills, and through bad mud holes. It's nice having all that torque, but hard on everything else. I would not recommend going over 25" (actual dia.) on tires.

[chris davison]

Im guessing 25 fpt on the motor a quick guess puts you at about 870 fpt at the axle. One # 60 chain driving 3 axles in series wouldnt be enough. My guess is you kept breaking that first chain. What was your top speed? Glad to hear you split the load and solved the problems. Im hoping I dont have similar problems. I actually have split the drive from the jack shaft it has two 15 tooth #80 sprockets one drives the 2 front axles the other drives the 2 rear all is # 80 chain. I have recently found that offset chain is the choice for low speed high load applications each link looks like a 1/2 link but it is made of high strength steel.

[chris davison]

opps I think you are closer to 1172 fpt at the axle

[Bw6]

The design/theoretical top speed was 35 mph., I never GPS it. This is due to the .6:1 (overdrive) CVT ratio in high. I doubt that you will have any problems the way you have split your load. The Vanguard 31 hp. develops 47.3 ft. lbs torque @2200 rpm.

[chris davison]

Wow I would never have guesed it was that high. Thats smelling more like 1646.39 fpt

[Bw6]

Wow I would never have guesed it was that high. Thats smelling more like 1646.39 fpt

Indeed, a lot of torque, and a lot of problems harnessing that torque.

[Stonewall]

Wow I would never have guesed it was that high. Thats smelling more like 1646.39 fpt

Wouldn't you loose some torque by putting it through all those chains and shafts, like you loose it in the driveshaft on cars and trucks, or did you factor that in already?

[chris davison]

Thats kinda hard to factor when you dont know the draw bar pull or weight of vehicle or how much drag the chain tentioners are causing but your right you will loose some. If he can climb a steep hill at idle and go 35 mph I dont think he is loosing much. Great job at designing Ray.

[Bw6]

Thats kinda hard to factor when you dont know the draw bar pull or weight of vehicle or how much drag the chain tentioners are causing but your right you will loose some. If he can climb a steep hill at idle and go 35 mph I dont think he is loosing much. Great job at designing Ray.

Sometimes, you get the bear, and sometimes the bear gets you.