Go Hydrostatic or not

[DanL]

I'm new to your forum and hydrostatic vehicles, except my John Deere Tractor. I love snowmobiling and I like driving my Snow cat. Now I would Like to combind them into one vehicle. I want to take 2 800cc two stoke engines producing A total of 346 hp and 226 ft lbs of torque. Total wieght of the vehicle around 1500 lbs. I'm taking 4 snow mobile tracs each with a foot print of 48"x15" 2 for the right side and two for the left. I figure on using two hydraulic motors on the right and two on the left using one hydraulic pump to drive them all. Not sure on how to steer it other than there other systems being used by snowcats. Does anybody know about how much this system would cost? Or would there be such a power loss that it wouldn't be worth it? I would like to get around 70 MPH. Any feed back would be appriciated.

[Snow_4]

You have way to much rpm engines for stat drive... Either reduce rpm with
a geartrain or find low rpm torque engine.
Im building a cat myself now and with a VW diesel engine spinning at 4500,
i had lot's problems finding good size pumps that come "close" to 4000 rpm...

[Ruckus]

GREAT PROJECT!

The 4-track snowmobile has haunted my dreams for some years...

yes, redrive is the name of the game. The larger the pump, the lower the rpm. ok, sure, there are exceptions. If you look up aircraft pumps they operate at 8,000 to 20,000 rpm. But they are hard to come by cheap (although they DO appear on Ebay from time to time).

But for many instances, you will need a redrive to achieve the correct rpm between engine and pump. No biggy.

My pump is 2800 max, my engine is 4000 max. The answer? redrive.

If you get quick-change pulleys, then you can change your final drive ratio in minutes.

Here is an aircraft redrive:


my hydraulic hybrid redrive:


there is no reason you can't build what you want using hydraulics, BUT, it will take time and careful research to properly match components to your project.

cheers

[diecycle]

Ruckus is right about the aircraft pumps. The also show up on the military surplus sites. Get two so you have extra parts. I have seen quality aircraft pumps at surplus yards for a couple hundred dollars that cost the US government over 20,000.

SAI makes parts that might suit your application, but they are spendy.

Unless you go surplus/ebay hydraulic systems are very expensive. The bad about surplus/ebay is a good chance to get crap or to get not what you wanted.

I shop ebay/craigslist often and have all the major hydraulic catalogs on my hard drive, including listings of the hydraulic parts of some lawnmovers and diesel welders. With this, and the occasionally call to the local hydraulic shop, I can usually figure out what is being sold and whether or not I want it.

On a final note, in my opinion, a two engine setup is more hassle than it is worth and since a hydraulic system is going to be somewhat of a hassle in itself, you are dooming your project.

Snow cats are not speed machines. Snowmobiles can be speed machines but they are setup differently. I have ridden in plenty of snow cats and they are not speedy. The ones I am familiar with drive like a tractor with power going to one track or the other to steer. This steering setup is great for hydraulics but not for speed.

The reason would be, in my opinion, to use hydraulic for your idea, is to control and utilize the power band in your engine with more precision and more efficiency than a mechanical transmission. If you wanted to get lots of torque to your tracks with a smaller motor than this would work well.

In a nutshell, if you want to build a small (one or two person) tracked vehicle that is slow and climbs anything, go hydraulic, if not, don’t.

(and either already have a plan/model or really think on the ass ache involved with a dual engine machine)

[diecycle]

I re read my post and a tracked vehicle dosen't need to be small to use hydualics, I was just thinking small because of the snowmobile/snowcat reference .

[x4158]

yeah, I wouldn't consider a bulldozer to be a small vehicle either...!

[DanL]

Originally Posted by Ruckus

GREAT PROJECT!

The 4-track snowmobile has haunted my dreams for some years...

yes, redrive is the name of the game. The larger the pump, the lower the rpm. ok, sure, there are exceptions. If you look up aircraft pumps they operate at 8,000 to 20,000 rpm. But they are hard to come by cheap (although they DO appear on Ebay from time to time).

But for many instances, you will need a redrive to achieve the correct rpm between engine and pump. No biggy.

My pump is 2800 max, my engine is 4000 max. The answer? redrive.

If you get quick-change pulleys, then you can change your final drive ratio in minutes.

Here is an aircraft redrive:


my hydraulic hybrid redrive:


there is no reason you can't build what you want using hydraulics, BUT, it will take time and careful research to properly match components to your project.

cheers

Remember I am a novice when it comes to hydraulics and converting the energy from mechanical to hydraulics then back again to mechanical is very basic. That being said lets say I redrive down to 4 to 1 easy enough to do now I'm at 2000 rpm. What Am I looking for in a pump? Do I do some math now that I'm at 4 to 1 ? Or do I regain the rpm by which hydraulic motors I install? Or do I redrive from the hyd-motors to the final drive (the tracs). By the way Ruckus how far are you in building your four tracked beast?

[dryice000]

another thing to remember that snowmobile engines are designed to run only with a primary clutch installed, they will start without the clutch but there it is hard to pull over and the run rough without a clutch, so if you are not using the belt drive system then you will need to make a flywheel.

snowmobile's are my passion and I think 2 stroke's are the way to go for power sport applications , but that being said I don't like using them as a utility engine, rotax 800 engine's make there hp at 8600 RPM so thats way over what most hyd pumps can handle and like i mentioned above, if your not using the CV belt drive then you have to make a Flywheel.

for your application there are many better engine options then 2 sled engines. if it were me I would be leaning towards a small diesel such as a kobota or yanmar.

[berg]

Here is an another approach ,4 cycle too



http://www.youtube.com/watch?v=45Mr6...layer_embedded


specs here..

http://www.forumsforums.com/3_9/showthread.php?t=34736

[berg]

I always thought a 4 tracked rig using snowmobile track would be cool.

Kind of a mini Tucker snow cat... the commercial tracks are too $$

I know you can get 176" molded replacement tracks new for around $800

Samurai would be a good platform and make it hydro steering IMO.