Longitudinal inline 2-3cyl to shaft drive concept

[JoggerFogger]

First post here, so bear with me.

So I'm trying to do my math and research before I dive into a diesel repower. I have a blank slate, and I want to do it (mostly) right the first time. I really like the BMW/Moto Guzzi type bikes with in-line 3 cyl 800-1,000cc diesel motors. It just seems to me that the biggest problem with them is getting the gearing to put the motor at a decent cruise RPM matched to a decent speed. I think you're all aware of this issue? Beautiful machines that are limited to 100kph on the rev limit 3600rpm.

This problem is easy to resolve with a laterially mounted crank, primary drive options, and with sprockets for final drive. The range of ratios are virtually unlimited. But I never liked the huge primary covers hanging off the side of American V-Twin bikes. I've seen several 3cyl motors mounted sideways in the frame, but it makes for a very wide creation.

Ideally, I'd like to see a cruise speed of 60mph (~100kph) at 2,000 RPM. I figured out that a 20" (50cm) diameter rear wheel needs to spin at 1,009 to hit 60mph. That means a net 2:1 ratio engine speed to wheel speed.

I also can only assume that someone, somewhere has tried this before, but I can't find anything to verify that assumption.

So here's my conceptual solution:



Sorry about my crude drawings, but I felt like words couldn't fully describe what I'm thinking. I'm sure the scale is all wrong, and I have no idea if there are pullys and belts or Chains and sprockets that will work in this application. I can fabricate all the mounting brackets and stuff that any decent garage head can do, but precise machining and sprocket building is beyond me. I'm guessing that the transmission will sit somewhere in the area of the airbox and battery under the seat of most bikes, but generally available space.

Another problem with finding a shaft drive bike here in the USA is that 90% of them are Japanese bikes, and the transmissions are cast as part of the engine case. Those few European bikes that have detachable gear boxes are too expensive on this side of the pond. I only state this knowing that this forum is predominately UK based. On the other hand, we have a large supply of V-Twin (aka Harley Davidson) and "Chopper" manufacturers of aftermarket stuff for Harley based machines.

Once I give up the idea of being locked to a BMW final drive, the options open up dramatically. I've owned a GL1200 Goldwing, and I'm thinking that it would make a great platform for this kind of contraption (if it will work). It's going to be heavy for sure, and I know from past experience that if you're going to dump a whole bunch of time and money into a project, you might as well end up with something that is comfortable, capable, usable and that you like.

I'd love to know if I'm crazy with this idea? If there's some obviously tall hurdles that I'd face? And if anyone else has successfully built something like this that I can just copy.

Thanks in advance,
-Kevin

[JoggerFogger]

I just realized that the space under the seat on a GL1200 is used by the gas tank. Might not be enough room there.

[DieselFly]

Here is another way of doing what you are thinking. http://www.youtube.com/watch?v=xnrX5DSY ... 90megP4JxE
Its well worth the time to look through Heiko's Youtube channel. He has done some very cool builds every way possible

[tappy]

I think you might have trouble making a clutch small enough to fit in the first driven pulley as shown. Not a great problem - do a few torque & speed calculations and work out where it needs to be, but I think replacing the standard flywheel with a clutch system might help keep installed length down.

If I recall correctly, the Kawasaki GT550 & 750 shaft-drive, aircooled 4s used pretty much the same motor as the GPz550 / 750 chain drive, and I *think* this was done by a sort of bolt-on bevel drive on the side of the gearbox. Either way, the shaft drive may be easier to incorporate, and those frames were certainly a lot lighter than a goldie, but perhaps not long enough for this plan.

Somewhere on here a guy put an inline diesel into a CX500 frame and used a CVT system where you're showing your belt drives. This looked a bit crazy but could keep weight and length down, and give a good broad spread of ratios.

Bear in mind that if you gear the final drive high for economy and cruising, you'll need a very low ratio to pull away, especially if you use something as heavy as a goldie! So the spread of gear ratios is important.

[JoggerFogger]

I would just use the clutch systems that Harley types use. That's where the clutch goes on all of them.... I think. I'm not a harley specialist.
That video that DieselFly posted is exatly the same CX500 that I think you're talking about. Very cool. CVT trannys are very cool too. I'm very much open to any ideas, and these are good ones.
I have a Honda Elite 150 scooter that has a CVT, and I'm amazed at how it works, and how well it works. I do know that they are not the most efficient, but maybe better/easier than 2 belts and a mess.
I just looked up the weight of the stock GL1200 motor and it's 360lbs. This modification might be lighter than the original.

I'm hoping that a 6 speed transmission will have enough spread to both launch well and cruise well. I'll have to do more math when I get to that point, but I'm also hoping that these Harley based transmissions have wide variances in ratios. But in the end, I'll sacrifice a tall 1st gear for a tall 6th gear.

thanks for the pointers!
-KM

[coachgeo]

for Space and simplicity.... IMHO the layout like CVT to shaft drive of the production Track Diesel is your best bet

[tappy]

I'm inclined to agree with coach - "add simplicity, add lightness" has long been an addage of successful designers.
A CVT system does have more losses than synchronous belts, but by the time you've added 2 belt drives and the harley transmission losses I think the reduced weight would win over.
It's possible to get a very broad spread of ratios with a well designed CVT too, and having a low engine speed at cruise might well save far more fuel than the extra losses will cost..

[Stuart]

I'd use a gearbox - going on the experience of others you'll have to strip the CVT pretty regularly to replace those pesky plastic bushes.

[coachgeo]

I'd use a gearbox - going on the experience of others you'll have to strip the CVT pretty regularly to replace those pesky plastic bushes.

Thanx for the input. Has not been mentioned in here before that I can recall. Which manufacture has gone to a plastic bushing? Course could one just go to a metal bushing and be done with it? Copper?

[DieselFly]

As with any design for power transmission system mating engines and transmission ment for other applications can often result in failure. The big killer is torsional vibration whick loves to eat teeth, bearings and shafts or anything hooked to them. My CVTech system has no arms or bushings like the one in the Track bikes it has the same insides. With over 6000 miles I have not had a single problem with the CVT portion of my drive train. I have broken a Jackshaft (lay shaft) and thats it. Belt wear has been awsome. And I think the key is that the clutch set is ment to work on industrial engines that red line at or below 3800 rpm. The extra springs and weights allow it to be tuned in this this range. Is it optimal no as its ratio range gives to much overdrive as it is ment for a small diameter rear wheel. Anyone who has ridden my bike no matter how hard core comes back laughing and cannot belive it works so well. The people that seem to like it most are the hardened Harley guys. Why its a V twin, vibrates, blows black smoke, knocks so bad it sounds like it will throw a rod any moment, looks cool and is something few around here have ever seen. Most of us don't have the budget to buy what we want so we build with what we find or buy cheap. I would love a Baker six speed hooked to a 40hp diesel but its not in my budget. I have been careful picking parts to get the best value. If you really want something to run around town and back roads one can't beat a Comet 40/44 series clutch and a 10hp Yanclone. You will have a nice little bike that goes 50-55mph all day. Hey throw a turbo in there jack it to 15hp now you have a 60mph beast. The saying at Lockheed when they design the U2 spyplane was "simplicate and add lightness". I'm starting to collect parts for the next bike and it will be a Yanclone turbo as described for my daughters 16th birthday in 1 1/2 years. The key is just build if she blows up. Build her again minus that parts that blew

[pietenpol2002]

No doubt the CVT option is the simplest and most efficient choice. But, it's not for everyone. Depends perhaps to some extent on your skill, available tools and "resources".

So, as long as we're brain-storming how about this. There are plenty of examples of mating diesels to the venerable BMW trans. And you can buy K100 gearboxes on Ebay all day long for $69.95 plus shipping (at least here in the states). I got a low mileage trans and clutch for $100.

Since you're going to be stretching and modifying the frame to accommodate the north-south oriented engine anyway, you have 2 options for achieving the final drive ratios that you desire. The first I've seen done but have no pics or links to direct you to. It involves a sprocket on the output shaft of the trans with an accompanying outboard bearing. Power is then transmitted by chain from the right side of the Beemer trans to the opposite side of the bike via a sprocket incorporated into the universal joint of a left hand final drive such as the Yamaha XS750 or XS1100. I didn't talk with the builder/owner but it appeared to work well. Ratios are easily fine tuned via the sprockets. Not brain surgery, but would be a bit of work.

The other option is to simply drive directly out of the Beemer box into a right angle gear box. Again, dial in the desired final drive ratio with the sprockets. However, unless you're a bit creative, it can make for a long bike. Below are 2 examples. The first example is the much maligned CX500. The second is likely a BMW derivative and unnecessarily long. We're brainstorming, right?

[JoggerFogger]

Yes, brainstorming indeed.

Just to make something clear: The 34hp Briggs/Vanguard/Diahatsu engine ($4,900) and the chrome Baker 6 speed ($6,000) were only used because it's pretty hard to find good images of parts in the right orientation. My project would consist of whatever I could find on Craigslist, and whatever I could find from my buddy who works in commercial diesels. I'm thinking a small diesel engine left over from a chilled container for under $1,000 and a used transmission from some project for $500. I've seen both on craigslist and random places. If I can get the concept worked out in my head, then I'll know what I'm looking for.

I absolutely love the idea of the left side shaft drive mated to a right side divorceable BMW tranny output. Could possibly only add a couple inches to the length. Would the motor have to turn clockwise? (looking at the rear)? Another interesting aspect of those pictures is the 90 degree gearing box. That opens a lot of options for final gearing, and eliminates altogether the need for a shaft drive. I just don't know where to find one of those little gems.

One of the benefits of using a HD/Baker/chopper style transmission is that it's so narrow. Not the mass of the transmission, but the input and output gears are sandwiched together. Even on the same shaft! If the primary drive were chain, and the transmission to shaft was chain as well, the length would be minimal. As I keep thinking about this, I'm amazed that I lucked out on the torque direction on the transmission. I hadn't thought about that until now. Maybe it's not an issue with the transmission, I'm sure the clutch and gears can handle reverse torque just fine. Just like engine braking torque.


These examples are most likely for more show than go. And I would imagine the chain slap is pretty annoying without a tensioner? maybe not. But the net length of the transmission could be less than 6 inches. It looks like (from pictures) the BMW bell housing + transmission + sprockets to shaft drive would be 17+ inches? With less length used by the transmission, there's more room for a motor. Or more room to fit a motor, as in putting the motor further back in the frame.

A CVT sounds like a great alternative. I just have my mind set on rowing my own gears. I want to be able to lug the motor. I want to control the gearing. Maybe my 2nd build will incorporate a CVT.

These ideas you guys have are awesome and enlightening. In my head I'm restricted to what's been done, or what I can imagine. Now you guys have opened up all those limitations and again it's a blank slate. I love it.

-Kevin

[tappy]

Last November when I was off work after a shoulder operation I designed a CVT system.
The reason being that I wanted the variability of a CVT system without the great big driving "clutch" mechanism sticking out on the end of the crankshaft.
The design used a CVT belt / sheave system, but was manually controlled so you still get to "row your own gears"... Most "off the shelf" CVT systems could probably be converted to do similar, and cost less, be lighter, and more or less simpler than using the transmission you propose.

Again - it's only a possibility / suggestion and you should absolutely do what you feel like

[JoggerFogger]

I obviously need to learn more about CVTs. And I'm totally open to different ideas. I just have it stuck in my head that gears would be ideal.
I might get to a point that the CVT just makes too much sense. Right now my perception of them is that they're great for scooters, and for some reason not good for heavy bikes.
Why wouldn't any big Japanese manufacturer use them on bigger bikes? (To that logic, why wouldn't any Japanese manufacturer build a diesel bike?)

I'm not challenging the idea behind it as inferior, I just don't know enough about it, and stating my current perception.

Wow, I sound like a douche. Just trying not to insult suggestions toward a CVT.

-Kevin

Quote I just read today that resonated with me: "It is the mark of an educated mind to entertain a thought without accepting it." -Aristotle

[coachgeo]

Last November when I was off work after a shoulder operation I designed a CVT system.
The reason being that I wanted the variability of a CVT system without the great big driving "clutch" mechanism sticking out on the end of the crankshaft.
The design used a CVT belt / sheave system, but was manually controlled so you still get to "row your own gears"... Most "off the shelf" CVT systems could probably be converted to do similar, and cost less, be lighter, and more or less simpler than using the transmission you propose....

this sounds interesting and deserves its own thread. Please do start a thread on this concept of yours. Would be a great conversation

[Rhynri]

Just as a note, some combines and some cars have incrementally adjustable CVTs as you describe. I'd start with those for inspiration.

[JoggerFogger]

this sounds interesting and deserves its own thread. Please do start a thread on this concept of yours. Would be a great conversation

Tappy,
If you do start a thread on this, or there's an existing place on the web that explains more about your project, I'd love to see it.
-Kevin

[Rhynri]

Seconded. I misread your post a little and didn't realize you had already designed the CVT! My bad.