Twin Engine Driveline

loppy

loppy

Member
#1
#1
I'm looking for pros/cons to hook-up 2 Raptor3's.

My initial idea is to have each Raptor in-line front-to-back, and each have a centrifugal clutch. A single #40 chain gets wrapped around each clutch gear then down to the first jackshaft gear. It would look like a triangle. A second jackshaft gear then goes to the rear sprocket. Several properly placed tensioners to limit chain travel and slap would be installed also. Question is, after each motor is up to speed and both clutch's engaged, will a faster motor clutch pull the slower motor clutch along, or will the slower motor clutch drag the faster motor clutch? It goes without saying that there will be added wear on the clutch's from the opposing forces. Also, if one motor quits, then its clutch would go into free spin imparting minimal parasitic drag to the running engine. And, an excellent chain guard will be mandatory. My concern is the safety of the clutch's and/or chain coming apart. Anyone with some experience with this?

All viewpoints welcome. Let's here it.
 
125ccCrazy

125ccCrazy

Well-Known Member
#2
#2
I had thought about doing this a while back with 2 clones..my thoughts were to use a single gear clutch on the first engine and then use a double gear clutch from a 2 speed set up on the secondary engine, run one chain from engine to engine and then another chain from the second gear to the rear wheel.... The biggest obstacle would be tuning both engines the same... Both engine will have to have the exact same build so they pull the same throughout the powerband....... Your ideas sound like your on track to getting this built....
Are both engines new or rebuilt the same as the other (i.e) both bored, milled the same?, same rods, pistons, carbs ect?
 
M

michaelkent

New Member
#4
#4
I think you could build up a single rapter engine for more horsepower cheaper than the cost of all the parts to make up a 2 engine setup, like having to lengthen the whole frame. Im into vintage racing karts and came across this. Im sure most old timers have seen it but its still a very cool 2 engine mini bike.
 
jeep2003

jeep2003

#5
#5
i think 125's idea with the dual sprocket clutch is better it seems like it would be easier to setup and less likely to fail. As long as the motors are built the same and the throttles are set exactly the same i think it should work fine
 
Oldsalt

Oldsalt

Well-Known Member
#6
#6
Would there be a problem with the two clutches becomming fully engaged with the engines slightly, or a whole bunch, out of sync? What would happen if, for instance, one engine was on it's power stroke and the other on it's induction stroke? Have been told by people that have never built a dual engine motorcycle or minibike there would be a big problem and they should know.

I don't know anything about power transmission but with the clutch arraingements both loppy and 125crazy outlined, it seems to me, that both would work fine. But wouldn't each engine be started individually by pull rope? Is that so? I'm thinking that's true. So the first engine is started and then allowed to idle. Now effort must be applied to the rope on the second engine. Now correct me if I'm out to lunch on this. If the second engine won't start unless the twist grip is turned a little [most often these engines won't start with the throttle closed] there might be a problem. I'm thinking that the engine that's already running will try to take off as if there was someone sitting on it when the throttle was opened a bit to facilitate starting of the second engine. But there won't be anyone sitting on it. The future rider would, at that instant, be standing beside the machine with one hand on the throttle and the other on the pull rope of the second engine. Maybe if the mini was snubbed up against the house or a handy fence all would work out OK.

I don't know. The subject is too complicated for me but I'd like to learn more about it if someone will take the time.
 
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cxbra

cxbra

New Member
#9
#9
Oldsalt said:
Would there be a problem with the two clutches becomming fully engaged with the engines slightly, or a whole bunch, out of sync? What would happen if, for instance, one engine was on it's power stroke and the other on it's induction stroke? Have been told by people that have never built a dual engine motorcycle or minibike there would be a big problem and they should know.

I don't know anything about power transmission but with the clutch arraingements both loppy and 125crazy outlined, it seems to me, that both would work fine. But wouldn't each engine be started individually by pull rope? Is that so? I'm thinking that's true. So the first engine is started and then allowed to idle. Now effort must be applied to the rope on the second engine. Now correct me if I'm out to lunch on this. If the second engine won't start unless the twist grip is turned a little [most often these engines won't start with the throttle closed] there might be a problem. I'm thinking that the engine that's already running will try to take off as if there was someone sitting on it when the throttle was opened a bit to facilitate starting of the second engine. But there won't be anyone sitting on it. The future rider would, at that instant, be standing beside the machine with one hand on the throttle and the other on the pull rope of the second engine. Maybe if the mini was snubbed up against the house or a handy fence all would work out OK.

I don't know. The subject is too complicated for me but I'd like to learn more about it if someone will take the time.
Click to expand...
If that were the case, all he would need to solve that problem is an engine stand. As far as engines being in sync, I highly doubt its as involved as you make it seem. The engine builders you were talking about were most likely talking about the merging of 2 engines into one? Since the engines running do the 4 strokes (intake, compression,power,exhaust) at the same rpm rate (as long as the engines are tuned the same), I dont think it would matter if one engine was on power stroke and one was on exhaust stroke because the engines are completely seperate, the ONLY thing that ties the two together is the clutch. Even if one engine completely died, the one engine running would still pull the bike smoothy like it had one engine to begin with. The dead engine's clutch would act as a chain tensioner (since it will be in free-spin mode).

I dont think a twin-engined mini is harder than the fabrication work it needs. Knowing that the two engines can be run by themselves or in tandem leads me to believe that the engines dont really rely too much on eachother, (but the slow engine will slow the faster engine down for sure though).
 
loppy

loppy

Member
#10
#10
Great input!

I started the build today. Cleaned up the frame a little in preparation for stretching. Stripped both motors and started to layout their orientation with relation to the jackshaft. Both engine's and the jackshaft will be mounted on the same plate. That sub-assembly will be mounted into the frame. It became immediately apparent the jackshaft needs to be behind the rear clutch so the second jackshaft gears chain clears its housing allowing an unobstructed path to the rear sprocket. I'll start posting pics soon.

In concept the slip (bias) is built into each clutch. As long as the clutch's in-fact slip, this will work. So in that respect, I firmly believe both engine's don't have to be built or timed the same. Because of that, the throttle design will have a little forgiveness, but will be as close as possible, of coarse.

I thought of building a built Raptor, and that will happen in another build, but this "twini-bike" build is an exercise in concept, design, and fabrication. Fortunately, I'm not letting this build be limited by dead presidents.
 
P

ProfessorJWN

New Member
#11
#11
Dad ran three engines on his pulling tractor, and those were in line and connected crankshaft to crankshaft.

I've been thinking about how a person could run two single cylinder briggs in tandem, and I think I have an answer for you.

I'd connect the single cylinder engines together half a cycle out of phase (i.e. one on intake, one on power stroke), that way they will function like a v twin. I was considering sitting the engines side by side and driving a common jackshaft either just behind the engines. On the jackshaft a beefier clutch would be installed, or a 2-speed as you'd get quite a bit of torque with this.

If I was gogn to use the pull starter, I'd put a "decompression" fitting on the second motor to ease starting. the primary engine then close it when the second motor fires up. (they would likely pop at the same time anyway, or very close.)

Realistically I'd install a small belt drive starter motor (with a centrifical clutch) on the jackshaft to spin the engines over.
 
Oldsalt

Oldsalt

Well-Known Member
#12
#12
cxbra said:
If that were the case, all he would need to solve that problem is an engine stand. As far as engines being in sync, I highly doubt its as involved as you make it seem. The engine builders you were talking about were most likely talking about the merging of 2 engines into one? Since the engines running do the 4 strokes (intake, compression,power,exhaust) at the same rpm rate (as long as the engines are tuned the same), I dont think it would matter if one engine was on power stroke and one was on exhaust stroke because the engines are completely seperate, the ONLY thing that ties the two together is the clutch. Even if one engine completely died, the one engine running would still pull the bike smoothy like it had one engine to begin with. The dead engine's clutch would act as a chain tensioner (since it will be in free-spin mode).

I dont think a twin-engined mini is harder than the fabrication work it needs. Knowing that the two engines can be run by themselves or in tandem leads me to believe that the engines dont really rely too much on eachother, (but the slow engine will slow the faster engine down for sure though).
Click to expand...
I guess a stand that could be put under the bike while the engines were being started would solve the problem. Good thinking!

You note that I am making the engine sync thing to be a bigger deal than it is. That's not really the case, I was only relateing what other experts, that, of course, had never built such a machine, had to say about it being a serious matter. Maybe there could possibly be something to what they say. It occured to me that the multi engined bikes that were pictured in the previous posts sported 2-cycle engines. Loppy is useing 4-stroke engines.

Maybe it would be handy to make that stand thats needed while the engines are being started to be foldable so it can be carried along by the rider. That way he could shut off the machine and easily restart so it would not have to idle while the rider had a smoke or stopping for a beer. But maybe it would be hard to make a stand that would not be dangerous to carry because if a guy fell off the mini the metal stand in his back pocket could really hurt.

Hey, I just now thought of this. How about haveing the first engine fitted with a 12 tooth clutch. It would drive a 12 tooth sprocket on the second engine. The output shaft on that second engine would also have another 12 tooth sprocket that woud drive a third 12 tooth sprocket on a jackshaft. The jackshaft would be fitted with a clutch and it's 12 tooth sprocket would drive the rear sprocket. I'm thinking that a set-up like that would allow the front engine to be started and when revved up high enough its clutch would engage and start the second engine. When the engines, now both running, were then revved up high enough the clutch on the jackshaft would engage and off you'd go! I don't know. It probably wouldn't work very well. But if it would it'd solve the starting problems.
 
george3

george3

Active Member
#13
#13
Starting prob. is no prob. standard clutch primary engine, doubble sprocket clutch secondary engine, second sprocket secondary engine to jackshaft or rear sprocket on wheel. Thats a done deal. Then use one of them old type motorcycle doubble leg kickstands that keeps the whole back wheel off the ground, all probs. solved. Oh yea disk brakes might be a good idea.
 
Oldsalt

Oldsalt

Well-Known Member
#14
#14
george3 said:
Starting prob. is no prob. standard clutch primary engine, doubble sprocket clutch secondary engine, second sprocket secondary engine to jackshaft or rear sprocket on wheel. Thats a done deal. Then use one of them old type motorcycle doubble leg kickstands that keeps the whole back wheel off the ground, all probs. solved. Oh yea disk brakes might be a good idea.
Click to expand...
That sounds like that wiuld do it! But why a disk brake?
 
Oldsalt

Oldsalt

Well-Known Member
#15
#15
george3 said:
Somebody posted a mini aready bilt that was real long, you could put 4 engines on it. LOL
Click to expand...
George

Is this the old picture you are talking about? A really dumb looking bike.

As I understand it, from some folks that really know what they are talking about, he made the mini with three engines because he could not get a fourth running! By that you can see that he really doesn't know what he's doing...no planning and no teknickle know-how.
 
Tragik

Tragik

Member
#16
#16
the one this guy had at Vintage Motor Bike Club in Portland, IN this year appeared to have a series of jackshifts setup on it, wish I took a pic of it now though

 
cxbra

cxbra

New Member
#18
#18
ProfessorJWN said:
Dad ran three engines on his pulling tractor, and those were in line and connected crankshaft to crankshaft.

I've been thinking about how a person could run two single cylinder briggs in tandem, and I think I have an answer for you.

I'd connect the single cylinder engines together half a cycle out of phase (i.e. one on intake, one on power stroke), that way they will function like a v twin. I was considering sitting the engines side by side and driving a common jackshaft either just behind the engines. On the jackshaft a beefier clutch would be installed, or a 2-speed as you'd get quite a bit of torque with this.

If I was gogn to use the pull starter, I'd put a "decompression" fitting on the second motor to ease starting. the primary engine then close it when the second motor fires up. (they would likely pop at the same time anyway, or very close.)

Realistically I'd install a small belt drive starter motor (with a centrifical clutch) on the jackshaft to spin the engines over.
Click to expand...
Joining them together would be the way to go, but I think he wants a budget build to run 2. It would be a LOT easier to run them completely seperate, you wont have to worry about timing and idle speed.. He could even run it with a stock motor up front and a modded one out back. In this case, he has the flexibility to do anything pretty much.
 
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