By DaveButler on Unrecorded Date: Edit

I am starting a project to construct an 8 wheeled ATV based on an Onan 20 HP opposed twin engine.

Inspiration for the project came from Jim Wolcott, whos work is at http://www.amphibiousvehicle.net/6x6.html

The engine is coupled to a Sears six speed 1995 garden tractor open differential transaxle.

(Three high gears, three low, 1 reverse high, 1 reverse low).

Currently, the transaxle is driven by a V-belt assembly, controlled by a tension idler clutch.

In english, when the clutch is not depressed, the belt has tension and drives the trans; step on the clutch, and the belt idles (goes slack and slips).

Steering and braking will be done via Comet disc brakes , mounted on the output shafts of the transaxle. The output shafts drive a pair of sprockets (one left, one right), which in turn drive a #40 chain, Max style, to 4 axles per side.

The frame is an aluminum double ladder style.

I am currently researching wheel bearings and wheels; any experienced individual in this area is graciously asked for advice...

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Dave, I would strongly recommend at least 50 chain and probably o-ring. Max hasn't used 40 chain for at least 25 years. And when you go to eight tires, you are increasing turning stress significantly. Might consider double chains like argo to be able to handle the weight and mechanical strain.

By Eugene Kochnieff on Unrecorded Date: Edit

Hi Dave,

Fred is right about the chain and 8 wheels.
It is easy to overcome however just raise the front and rear axle by 1/2-1 inch this will reduce turning stress and not affect traction one bit as any surface soft enough to let the center 4 wheels sink 1 inch will then get all 8 tyres. This approach also helps with climbing and decending obstacles. There will be however maximum stress during turns in soft material, but being soft it will yeild.

I rather like the idea of a 10 x10 with the front and rear axles raised maybe 2 inches.

Bye.

By DaveButler on Unrecorded Date: Edit

Hey, Guys!

Thanks for the input.

I didn't know that the new Max machines had moved to a larger chain.

Fred - do you have a good source for sprockets that will fit a 1.5 to 2 inch OD solid axle?

Jim Wolcott gave me additional advice, which I am posting here for all those following along:


"First problem is the trans, why build an allterrain vechicle and only drive one set of wheels.

When you get in mud or water only one side will drive. The best setup by far is the T20 used in Max and many other atvs. Don't waste your time with the tractor setup it won't work well. Second problem is chain size of #40 its way to small, Max only used it on there early machines. Number 50 or 60 is just right unless you want to use a much larger engine. With the larger chain your sprockets will last much longer. And your chain will not stretch nearly as much.
The disk brakes to steer with need to be as large of a diameter that you can fit. I made some about 12 or 13 inch diameter and used cheap automotive calipers. Use some front wheel drive ones that have a parking brake mechanism in them.
The bearing choice will depend on what you can afford, i used the good ones and they outlast the cheap stuff by far. Dont skimp on axle size, 1.25 would be minumum diameter, 1.375 even better.
I wouldn't make the frame from aluminum ! I would use steel for ease of fabrication, strength, and ease of repair or modification later on. You might not always be near a tig machine if something breaks !!!!
I used .125 5052 marine grade aluminum, its strong as all get out, bends well, and welds really nice."

By DaveButler on Unrecorded Date: Edit

Based on the input, I am changing the following:

1. A second frame is going to be fabbed from steel, for testing.

2. No doubt, I am using 50 or 60 chain, o-ring style, double row. I am sourcing now.

3. I spoke to Richard about purchasing a T-20 trans, which he recommends over the Argo trans.

I am still experimenting wih the straight cut trans out of the tractor, but with a locking center diff.

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Sorry Dave, I'm not into fabrication and rebuilding. I don't have a source for anything. I stick to factory parts and only deal with the Max machines. I worked on one Hustler for a fellow, but that was an exception and probably won't be repeated.

By newmax on Unrecorded Date: Edit

dave you can get sprockets from mcmaster-carr.com

By scrambler71 on Unrecorded Date: Edit

looking for 1in 316 bore shaftcoupling
can anybody help me on this
i am trying find a company who sell
1in 316 bore shaftcoupling
because i am changing my three bolt hub and
flanges to four bolt styles
for my 71 scrambler
i have tryed grainger msc
and mcmaster-carr.com
any help would be great
thank every body
daveyoder

By Bill Vincent on Unrecorded Date: Edit

Dave: How do you plan to convert the lawn tractor diff to a "locker"? Won't you lose the differential action if it is a locker? Just some random thoughts! Good luck with the project, and keep us up-to-date.

By DaveButler on Unrecorded Date: Edit

Hey, Bill.

The answer is that you are correct - I have to be able to lock and unlock the diff.

I have been noodling with a cable based locker based on an ARB air locker.

McMaster and Bailey are gems for parts - and a number of karting website aso have a great collection of brakes and gear hubs!

By Damen T.Hill (Argoss) on Unrecorded Date: Edit

heres a couple good sources for brakes mxk.com emmick.com they are both kart manufatures.

By shane forsythe on Unrecorded Date: Edit

fred

you said use doubble chains.
won;t that make a lot of noise/extra weight?

By David Keeso (Argomag) on Unrecorded Date: Edit

IF you use a single chain, it is not as strong. Double chain = higher durability longterm.

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

shane, yes, it will add weight, but with a heavy machine and steering resistance, it is an effective way to reduce the amount of chain maintenance. All chains stretch independently; with two chains, one does the work for a while until it streches too much and then the other works for a while. This alternating of chains allows twice as many hours between adjustments. It will cost twice as much to replace them, too.

By shanne forsythe on Unrecorded Date: Edit

thanks fred and david.

grate info
i was wondering if anyone has thought of building an aatv like the max with all the parts of a max but doubbling the size of everything, e,g, 2x as big t20 , 50hp 4cycle, 12wheels(duels),6.5feet wide(2000mm in metric) 118inches long (3000mm in metric)
it would have the same psi on the ground as a max2 with 5+seats 2x the cargo area.
with the same proven performance.

p.s. check out my idea at the bottom of the "lets build a dream atv" topics list
or use the key word search for "16x16".

see what you think.
shane.

By shane forsythe on Unrecorded Date: Edit

fred and david

sorry about the last post
the keyword search topic should have been "lismore".

shane.

By Dave Butler on Unrecorded Date: Edit

OK - As per the off board advice, I have restarted my project by going back to the basics.

I drove down to Fla. from NY and met with Rick (of RicksToys) and purchased his Max IV (circa 1979 model).

I now have a Max to use as the basis for all of my designs.

Starting with the basics - this unit has single chains to all drive wheels, and two fairly large discs for parking brakes.

The T-20 is in place, and I now see that what ATV guys call a torque convertor is to car and truck guys a CVT - constantly variable tranmission.

You all were correct - buying this unit has put me on the right track.

I am putting my 20 HP Onan into this unit for testing.

Question; with 20 HP, which CVT / convertor should I use?

By George on Unrecorded Date: Edit

As far as I know, the decision is usually based on wheather you are using a 2 or 4 stroke engine. Primarily it has to do with the RPMs and how much the converter opens or closes based on the engine speed. After that, I guess brands are a matter of personal preference and how much space you have to work with (and ofcourse, money).

By John Martin on Unrecorded Date: Edit

Dave-I would try and use a Kohler 25hp/20hp instead of the Onan motor. The reason is the throttle response. We have a Max IV with the 25hp Kohler and it has excellent throttle response due to an accelerator pump like device on the carburetor. In six-wheelers, unlike on lawnmowers and other equipment, you have allot of rpm changes going on where as on a lawnmower you just adjust the throttle to where you want to mow and leave it. I bought a Onan 20 for a replacement engine for my JD 316 garden tractor a few years ago and it works fine for mowing but the throttle response is no where near as quick as the Kohler 25hp engine. The Onan just doesn't react fast enough to throttle input to be a great motor for a super AATV. I guess it will work all right for a test but I would drop in a 25 Kohler for some good stock crate engine performance. I have heard others praise the B&S 23hp but I have no experience with that engine. Same goes for the Honda 20hp, I’ve heard they don’t have the quick response becasue of the lack of an acclerator device to provide enough fuel as soon as you hit the gas. I do have a 16hp B&S in a Max II which is pretty responsive to the throttle input but still not up to par with the Kohler 25hp. As far as the converter I would use the same one as RI uses in their Max IV. They have a monopoly on that particular drive clutch so for it you will have to pay premium if you want a new one, but you might always be able to find a used one for a bargain. Comet Industries makes many different versions of drive/driven clutches but the ones used in the Maxes are only sold to RI as far as I could tell when I was trying to find one. Used ones will probably be the best bet. The torque converter that came with the Max you bought might be the same as the newer ones depending on what engine you old Max had. The drive clutch is the one on the motor and the driven clutch is the one on the T-20. If the old Max had a four-stroke engine I would think your drive and driven clutches would work with your newer motor that you plan to install. The only other problems you might face are the diameter of the hole in the drive clutch vs. the size of the output shaft on your new engine and the key-way size being to big/small. Good luck with the project and keep your progress posted.

By newmax on Unrecorded Date: Edit

does anyone have any imput on what motor to upgrade to. a 23 briggs or 25 kohler. and what modifications would i need from an 18 hp max 4

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Mike, For the best performance, I would recommend the 25 HP kohler. You would then have a 900T. RI has done all the figuring out for you and can tell you just what to do and what is needed. It will cost a little more because you will have to change the driven pulley because of a larger shaft and beef up the motor mount frame because of more HP, but you will be amazed at the increase in performance especially when using tracks. The bigger diameter drive pulley is what gives the extra performance.

How did you come out with your driven pulley problem?

By newmax on Unrecorded Date: Edit

Thanks Fred, did you say i would have to change the driven pully or the drive pully? i have not got it back from my dealer yet. so i havn't heard anything yet. i am going to call him tomorrow.

By Fred Sowerwine, Montana's Max Dealer (Fred4dot) on Unrecorded Date: Edit

Well, Mike, I guess I said both. I meant to say Drive pulley. It is my understanding that the drive shaft of the 25 HP Kohler is larger than the drive shaft on all the other engines used.

By John Martin on Unrecorded Date: Edit

newmax-I would check and see where you get you engines. I ordered a Kohler 25hp for my Max II from Tulsa Engine Warehouse in you guessed it Tulsa, Oklahoma. They have all kinds of different options for the 25hp Kohler motor like output shaft sizes and optional output shafts on the fan side even. You should be able to find a Kohler 25hp with a 1" output shaft. I think mine is an 1 and 7/16" shaft, I'm not for sure on my engine, I would have to check but I do know they come in many different sizes and you could match the same size drive pulley you have now. The most important part of the conversion is to make sure you keep the same distance from the drive pulley to the driven so you will be able to use the same drive belt. If your 18hp engine is a Kohler then the wiring harness may be the same or you might have to repin some of the wires to have it correct for your factory Max harness. I am under the understanding that the drive pulley for all the newer Max IV (four stroke 90s up ???) is the same but only has different diameters on the inner hole. With the conversion on the Max II since it uses a smaller drive pulley I replaced that pulley with the one off a Max IV to use with the bigger Kohler 25hp. If the drive pulleys happen to be different you could probably still find a Kohler 25hp with the same output shaft diameter as your current 18 hp Kohler or B&S and stay with the drive pulley you already have. I would also only upgrade to the 25hp engine if your Max has the splined axles because I think they make a world of difference keeping the play out of the axles where the bolts start to wobble out the holes through the axles. Hope this helps you out a little.

By Timothy Schotanus (Mudbuster) on Unrecorded Date: Edit

I don't think the kohler 25hp is available with a 1" shaft(I could be wrong) I think 1.125" is the smallest. If you have a briggs now you would have to change the drive pulley as well.

By John Martin on Unrecorded Date: Edit

Another option I used for a conversion of my JD 316 garden tractor was to have a machine shop tool me a shim so my new engine’s smaller output shaft would fit my larger factory electric clutch. The shim was keyed to fit my new engine’s out put shaft and had another key cut to fit my electric clutch. It cost $50 which is still cheaper than buying a new drive clutch. I was using a 20hp Onan Performer engine I order from Northern Hydraulic catalog. I have over 150 hours on my JD 316 since the conversion and haven’t had any problems with the shim. If I would have bought the correct engine from JD it would have cost me almost double and I would have a smaller HP engine. My JD 316 originally came out with a 16 hp Onan when it was new in the early 80s and now with my newer 20 hp it is that much more of a best at less of a price and now a JD 316ss(super sport).

By chris davison on Unrecorded Date: Edit

One thing all can do is look in the yellow pages for a bearing house like king bearings or motion ind. They have a wealth of knowledge on bearings seals clutches and catalogues on all with eng info.