Chain Drive Tracked Vehicle

I'm in the process of building a tracked snowblower using a 53hp VW Beetle engine and transmission. In order to slow down the speed from the
output from the tranny I want to use a double reduction chain drive. Hopefully this will propel the vehicle at a decent slow speed in either first or second gear. I know some of you are going to say why not use a hydrostatic drive. One reason is size for this vehicle would dictate a rather large drive which would probably be cost prohibitive. Also I have a majority of the material already for the chain drive. Perhaps in the future I might be able to get a hydrostatic drive from a farm vehicle, such as a haybine at an auction, but for now it'll be chain drive. If anybody gets the Farm Show Magazine, there is a picture of a homebuilt tracked vehicle by a guy up in Minnesota by the name of Larry Brown. This is close to what I would like to build. I already have the frame welded together. Next step is to build the tracks.
So here's my question, what size chain should be used for the given hp and application? Seems like motorcycles use quite a large chain to drive the rear wheel, would that size be about right?
Regards, Bernd
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Motorcycle chains should be up to the power requirements. Motorcycles with considerably more power use chain or belt drives. If you're not in possesion of the sprockets, I'd suggest considering the motorcycle belt drives as being less maintenence headache over time - they do need to be well-aligned to begin with, but they stretch less (thus require adjusting less) and attract a lot less dirt & grime to themselves. The inexpensive and practical approach to that is probably to drop by a M/C junkyard - new prices tend to be a bit shocking.
Another (inexpensive, junkyard) approach would be to slap in a second automotive (or M/C) transmission, driven from the first one - gives the ability to change your ratios easily if you guess wrong, since it's a prototype.
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Are these belts cogged by any chance? Also do you have any rough dimensions as to width of belt. I had forgotten that the Harley uses belts, right?

Don't know if your familar with the VW tranny, but the motor mounts to it in the usall way. But the final drive is also in the transmission. No drive shaft to attach another tranny. I had thought of this but is very difficult to do. I should take a picture of the tranny sitting on the frame you you can see what it looks like. All I need to do is get all the junk off of it the has acumulated on it over the last several months. Since it's going to be a nice warm weekend here in NY, I might just clear things out and take a picture and post it.
Thanks Larry for the info on the possibility of using a belt drive. Hadn't thought of that.
Bernd

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Yes they are cogged. Yes, Harley has been using them for quite a while now. Kawasaki used them for a while on some bikes. Not sure what current production is using them. My bike is a shafty, and old. I was skeptical of them when I first heard of them, but the more I learned about them, the more they seemed like a heck of a good system.
Typically a bit over an inch wide, IIRC, but they can be had in many sizes.

Duh, right, it's a tranny and diff all in one (aka transaxle). I had a Corvair for a few years myself if I'd just engage my brain about what you are starting from - The main thing I recall about our aircooled VW was that it would be a royal pain to start at home, and behave perfectly when at the VW mechanic; and 9 (2-string) haybales fit (more or less inside) the van.
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Far and away the major cause of cycle chain "stretch" is wear due to road dust/grit.
Enclosing the chain fully in a case with an oilbath will remove this.
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On Sat, 29 Jan 2005 12:49:12 -0400, "jtaylor"

Of course, if the chain is run in an oil bath it must be sealed very well, otherwise along with oil leaking out you will get water and dirt leaking in. Since the chain can be lubed safely with chain lube and left to run that way maybe just having a good dust cover would do. The belting mentioned earlier is indeed toothed belting. It won't stretch and won't wear at the pins like chain and appear to stretch. It's expensive. You can get a toothed pulley made from aluminum which would be cheaper than a steel one. Several years ago I needed to buy some chain but did not know how to specify it. I called a local supplier, Washington Chain (I think), and the fellow I spoke to asked about my application, what speed, HP or torque of the motor, and environment the chain would be running in. With all that info he was able to give me a couple options and I was able to order the chain. The whole phone call lasted about ten minutes as I had all the data in front of me before the call was placed. I'm usually not that organised. If the chain is very long an idler may be needed. These can be made from plastic. UHMW works well if the idler as just a block that the chain rubs against. If the idler rotates then nylon, Delrin, or Acetron will work well. Delrin and Acetron don't absorb water, nylon does. I have seen power transmission parts pretty cheap on ebay. Another source is to google for "surplus _____". You fill in the blank. BTW, did you know that the ring gear in the VW transaxle can be switched to the other side? Then you can have 4 speeds reverse, and one forward. ERS
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Yes I did. That's how they made the mid engine formula Vee's that used to race at Watkins Glenn many moons ago. The VW dealer I bought all my cars from had a sales man that was into racing the Vee's. He had his car on display at the dealership. Almost got into racing back then but my dad talked me out of it. DARN
Bernd
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"Ecnerwal" wrote: Motorcycle chains should be up to the power requirements. Motorcycles with considerably more power use chain or belt drives.(clip) ^^^^^^^^^^^^^^^ However, remember that a motorcycle develops full power at around 100 mph, while a snow blower goes, maybe, 3-4 mph. If you really need 50 HP at that low speed, the chain tension will be about 25 to 30 times as high. However, I am not clear on the concept. Isn't most of the power going to be used to throw the snow? How much will actually be used to drive the wheels, and how are you planning to divide it?
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The engine that I'm using, a 4 cylinder opposed VW air-cooled engine, happens to be around 50hp. Remember I said I'm using the stuff I have laying around. I'm just going to try to put it all together in a project. So with that said the engine will drive the vehicle and a separate engine, 10 to 15 hp will drive a detachable snowblower. I'm going to upload a few more pictures to make it clearer as to what it will look like.
Bernd
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Bernd wrote:

My hat is off to you. Someday I hope to be able to move out of surburban Washington DC and have the space to tinker with stuff like you are doing. ;-)
-- Mark
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Thanks Mark. I'm going to document as much of this build as possible and then put it up on the web. The project is stalled because I needed to figure out how I was going to do the track. But that has been solved now so hopefully this spring I'll get it going again.
Bernd
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I think you have it backward, I'd use the 50 hp for the snowblower and the 10 hp for drive.
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I used to have a Massey Ferguson 12hp garden tractor with snowblower. It worked quite well in the snow. Don't need much to turn a auger and a 2 foot dia. impeller such as used on centrifugal fans. Besides that is what I have available to put together the vehicle. If the blower motor isn't big enough I can always get a bigger motor,eh?
Bernd
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I'm sure some of you would like some pictures to look at so here are 3.
First is the frame of my vehicle on the garage floor before welding.
http://kingstonemodeleng.com/vw/vw1.jpg
I should have turned the picture 90degree ccw for better viewing. Sorry.
Next is the "Home-Built Tracked Vehicle" by Larry Brown.
http://kingstonemodeleng.com/vw/track001.jpg
And here's the whole article about the vehicle.
http://kingstonemodeleng.com/vw/track2.jpg
Enjoy, Bernd
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Go here www.emerson-ept.com, you must register to git in da gate but might be some good info. I didn't register so don't know. Dese boys own morse chain, and browning gear and prolly have lots of info. Looking at what yer building I'd use 80 chain. Prolly over built. Maybe git by wit 60. I've changed enough chain to know bigger is better. If you have the space. If you break something it won't be the chain, prolly the key. ---------------------------------SNIP-----------------------------------------------

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wrote:

Thanks Mike.
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In article <77QKd.112415$w62.107806@bgtnsc05-

Another way of looking at the chain size is to consider that the tension in the final chain will be approximately
max traction X (diameter of the track drivers / diameter of the final sprocket)
I'd expect the maximum traction to be something on the order of the weight of the vehicle.
The chain manufacturers publish tables for max chain tension for slow speed drives, which is approximately 1/4 of tensile strength. If you go thru the standard selection procedure you'll end up with a massive chain that's suitable for 24/7 use--the slow speed ratings are probably a better fit for your use. Here's Dodge's version...
www.dodge-pt.com/pdf/catalog/ pt_components/sproc_sel.pdf
Tsubaki gives actual tensile (breaking) strength in their catalog, and a Google search may turn up their catalog online.
Ned Simmons
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I've uploade a few more pics for those that want to see how far I've gotten and what it looks like at this point in the project.
http://kingstonemodeleng.com/vw/frame1.jpg
This picture shows the frame all welded up and the tranny with shift, by the way it'll be a four speed, mechanism setting on the frame. The frame is 7 feet long and about 30" wide.
http://kingstonemodeleng.com/vw/tranny1.jpg
This is a closer veiw of a 4 forward and one reverse speed aluminum VW transmision. From lower rigth to upper left is as follows: bell housing, differential, trannsmision, shift linkage. The drive from the tranny is through two sets of constant velocity joints, one on the tranny and one on the wishbone trailing arm holding the rear drive wheel.
http://kingstonemodeleng.com/vw/tranny2.jpg
Here's a closer view of the transfer part of the case. The constant velocity joint is bolted to this part with 6 bolts. I plan on makeing somethign out of round stock to were I can wweld a small sproket and bolt to the drive axle, just like the original velocity joint.
I hope I've cleared up some questions on my project as to what it looks like and why I'm doing the things I am. I have 4 front wheel drive VW's setting around and a Beetle chassi that was once used for a dunebuggy I had. So I'm using the parts from these to build the snowblower vehicle.
Bernd
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I'd second the idea of a second tranny for the wheel drive. Start out with a reduction of about 4:1 (rear end ratio) and then you can gain another about 3:1 or more reduction by the gear selection. Having the gears in a second tranny will also allow you to have 4 choices for speeds which will make the depth of the cut for the snowblower adjustable for the various depths of snow. You're probably going to be wanting to do about 3mph when the engine is turning for 60mph on the first tranny so that ends up with a reduction of about 20:1 and that means that you need to have about 5:1 for the intermediate reduction to the second tranny clutch something easily possible with a chain drive. Please also note that chains are transmitting tension, not torque so a larger gears will allow for more power transmission for any particular chain size. You're also not going to be transmittng that much power (maybe 5hp) so the requirements are not going to be that hard for the chain drive.
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