Coupling Two Engines: Best Method & Firing Order?

[wolram]

I have in mind to recreate a Brit v twin (in a fashion) using two single cylinder engines coupled together, as i see it i have three options for the linking method, chain, toothed belt, or gears, gears would be the most (ridged) coupling, the chain and belt would have some flex, the other consideration is the firing order which may effect the coupling.
Any one have an idea as to the best coupling method, firing order?

 

[Danger]

I assume that these things have a side-shaft output, which eliminates the easy way. That is to directly couple the crankshafts together in line.
The firing order shouldn't matter at all, unless the difference sets up some sort of vibration. The tricky part is making sure that the rpm's are synchronized, which means tweaking the carbs and timing a lot and making sure that the advance mechanisms work together. If you can do that properly, I'd go with a gear connection; if not, you'll need something with some built-in forgiveness like the belt.
Of course, you also have to consider the physical layout. Make sure that whatever you do will properly fit in the frame without any parts getting in your way while you're riding it.

 

[brewnog]

Since it's a twin, the firing order will be one then the other...

As Danger says, mechanical coupling will be a piece of wee compared with trying to synchronise the carbs.

 

[turbo]

Synchronizing the carbs is not as touchy as synchronizing the ignition systems, especially if these are older motors with mechanical (points) ignitions. Those are very touchy.

 

[wolram]

Synchronizing the carbs is not as touchy as synchronizing the ignition systems, especially if these are older motors with mechanical (points) ignitions. Those are very touchy.

Points? i would go go electronic, and if i can set triple SUs i am sure i can
sync two amals, it is the power pulses on the drive strain i am most worried about, many double engined machines tend to explode the coupling,

 

[FredGarvin]

Points? i would go go electronic, and if i can set triple SUs i am sure i can
sync two amals, it is the power pulses on the drive strain i am most worried about, many double engined machines tend to explode the coupling,

I would use a geared/splined connection simply because of the rigidity I would think you would need in terms of the firing timing. Since you really can't have compliance in the coupling, I would also consider that, since a splined or geared coupling is expensive to make properly, that you include a shear section somewhere between the coupling. That way when all is working well, the teeth of the coupling are lined up and taking loads as designed. However, when weird pulses come in that can mean dynamic forces much higher than standard operating forces. A shear section in the coupling design would save the expensive parts of the coupling and preventing other things from being damaged due to oscillations, etc...

 

[wolram]

Fred if i use a compensating ignition between the two engines, would a shock
absorber on one engine drive shaft, throw it out?

One engine is the (master) and via electronics tells the other when to fire, if the mechanics are in sync.

 

[Danger]

Excellent suggestion, Fred. I never thought of a shear coupling, but it could certainly save a lot of big-buck repairs if things go south.

 

[FredGarvin]

Fred if i use a compensating ignition between the two engines, would a shock
absorber on one engine drive shaft, throw it out?

One engine is the (master) and via electronics tells the other when to fire, if the mechanics are in sync.

I honestly don't know Wooly. I have never done or know of anyone who has done something like this. I was thinking in terms of the mechanics of the coupler itself.

The one thing I really don't know about is the effect of having one engine constantly changing speed due to the compliance in the coupling. I think you would know better than I do on that.

To answer your question about the shock absorber, I would have to see what exactly it is you are thinking about using.

Sorry I'm not much help in this. It does look like a fun project though.

 

[brewnog]

The problem with a 'soft' coupling between the two would be that over the intended speed and load range of the engine, you could very well set up some horrendous torsional vibrations which could destroy the crankshafts, and not necessarily after failing whatever 'weak link' you built in. You'd have to carry out a full TVA to save the risk of smashed engines (or worse).

 

[bigjsp]

you might enjoy my little project

an S-10 pickup with TWO 355 cubic inch (5.7L) coupled inline.

I had looked at using chain couplers like older tractor pullers and drag racers but since these motors can turn 6000 RPM + I wanted a better way to keep the grease in place.

I added a second key-way to a Fluiddamper brand harmonic balancer and the rear engine crank onto the rear engine. I built pieces to connect to a Zurn industries 800 hp electric motor coupler. The Zurn coupler allows up to 0.050 of misalignmentand up to a degree of off angle. It is basically a splined sleeve with 2 pucks which have teeth that engine the splines, It also has o-rings and can be filled with grease through pipe fittings.

Each engine has its own carburator, alternator, ignition, fuel pump and cooling system.

The power then proceeds through a normal torqueconvertor turbomatic 400 transmission then a driveshaft and a ford 9" rear.

video from the first time we started it
http://www.livevideo.com/video/AA2314920EAE49988BDC6036C51A5E9A/twin-engine-v-16-s-10-truck-first-time-running.aspx

car show awards - this is from last weekend :) 1600+ cars! It was a big win. So I'm still pretty excited about it.

http://www.livevideo.com/video/CF738C9B4164418387BE6759E9E71D7B/award-presentation-arthritis-c.aspx?m_tkc=5535906


http://s-seriesforum.com/albums/album168/Nats06_130.jpg

http://www.dropndrag.com/images/shows/2006/snat/pages/DSCN1291.html

 

[wolram]

That is one cool vehicle, your win was well deserved

 

[Danger]

Welcome to PF, Bigjsp. Very sweet machine you have there.

Woolie, I just thought of something, but I have no idea whether or not it has merit. Since these thumpers of yours will be in very close proximity (compared to a couple of multi-cylinder engines), would you be able to use a single carb with a manifold feeding both? Also, what about a 2-cylinder distributor driven by one engine and firing them both?

Just 'Ivanating' here.

 

[bigjsp]

Thanks, there are a lot of details and challenges which make the building of unique things fun.

In talking with many different owner/ builders of twin engined dragsters and older style mechanically coupled tractor pullers everyone basically says that horsepower on a shaft is horsepower on a shaft. They said they made the same power and broke the same amount of parts regardless of timing and connection 90, 180 or what ever it just happened to end up to make it back for the next round of competition. Mine are at 45 degrees just for emotional purposes.

Even with 2 cylinders think about the V twins that are at 45, 60 or 120. Not exactly symetric


Wolfram, what is the end vehicle and what motor "display" are you going for

also what type motors and displacement?

 

[wolram]

Danger, i have not been lucky enougth to find two engines yet:grumpy i thought that would be the easy bit but, Brit bike stuff seems to have dried up.

 

[wolram]

Thanks, there are a lot of details and challenges which make the building of unique things fun.

In talking with many different owner/ builders of twin engined dragsters and older style mechanically coupled tractor pullers everyone basically says that horsepower on a shaft is horsepower on a shaft. They said they made the same power and broke the same amount of parts regardless of timing and connection 90, 180 or what ever it just happened to end up to make it back for the next round of competition. Mine are at 45 degrees just for emotional purposes.

Even with 2 cylinders think about the V twins that are at 45, 60 or 120. Not exactly symetric


Wolfram, what is the end vehicle and what motor "display" are you going for

also what type motors and displacement?

I am looking for two 500cc singles to put into a modified motorcycle in a
v arrangement, all the major parts will be pre 1960 for a classic look, i am not looking to build a show winner, just some thing functional.

 

[bigjsp]

http://www.bigbikeriders.com/48cyl.htm

another idea to consider