Coupling multiple engine onto one drive shaft

[triniajy]

I’ve been searching high and low for an answer to this question. What actually HAPPENS if two engines were to power one drive shaft? I heard back in the days that cars were built this way to break speed records, and I heard present day it is used in tractors, but what increase.

My question is what is affected HP, torque, acceleration, what are the advantage of connecting multiple engines together?

Saying if they are the same make model, connected properly, and synchronized, you know all the rudimentary stuff.

 

[DickL]

Quite a few helicopters use 2 or more engines connected into a single drive. The one I'm most familiar with it the CH-46 (a pretty old one, but still in service). It use both engine speed synchronizing and torque balancing. As I recall the speed synchronizing was by an automatic control, the torque was by pilot control or trimming of the fuel flow.

Using multiple engines is one way of increasing the total horsepower available. In aircraft and some other applications it also provides redundancy for safety and reliability.

 

[triniajy]

If I connected two 5HP motors together, I am pretty sure that it does not make a 10 HP set-up. Is there an equation that is used to find this quantity of HP being produced?

a transfer case looses about 25% HP so does that means it would produce 7.5HP?

 

[DickL]

Power in equals power out, less losses. If you have an ideal (0 losses) combiner gear unit, then you'll get all that power (10 HP) back out, assuming they are synchronized.

I've not worked with transfer cases, but a 25% loss in power through any of the gear units I'm familiar with would say something is badly broken. Most gear units run in the upper 90% efficiencies.

If your motors are induction motors, synchronizing them is almost automatic if they are fed in parallel from the same supply. If your using IC engines, then synchronizing is a bigger problem. The applications I've been around either had fairly complex controls for syncing or they had a main engine (bigger) that was controlled and a secondary engine (smaller) that sort of followed (ah, this is a very simplified version of how they are synced.

 

[Antiphon]

You don't just tie the shafts together; there must be something like a transmission/universal with two inputs that allows both engines to rotate separately.

The universal joint on the back axle of a rear-wheel drive car is a start. Put two engines where the wheels are and take power from the drive shaft.

 

[brewnog]

You don't just tie the shafts together; there must be something like a transmission/universal with two inputs that allows both engines to rotate separately.

Only if (for some reason) you want to operate them at different speeds. If you're happy to run them at the same speed, you can connect the crankshafts together directly with no need for a transmission/differential/gearbox.

In this case, the question of synchronising them isn't the complex issue people commonly think. My favourite analogy is of two people riding a tandem; both prime movers (people) can apply different amounts of effort with no problems at all; the power transmitted to the driven equipment (back wheel) is just the sum of the power generated by the individual prime movers.

 

[Dotini]

I have coupled two 2-stroke Yamaha KT-100S kart racing motors together successfully enough to win numerous races with this setup. The motors drove drive belts to both sides of a single axle clutch. I ran them 180 degrees out of phase. I have a friend who took two of the same engines and tied the cranks together to form a twin. He ran it successfully for several years with the motors in phase.

Respectfully submitted,
Steve

 

[StuckOnZero]

No skill is needed to couple two engines together. A V8 is essentially 8 one-cylinder engines tied together. Large ship engines come in 4,6,8,10,12,14,16 cylinder versions. Several auto companies, including Renault and Audi, have built 'W' engines by chaining together two V-4 engines. The only difficulty is if you desire to run down one or either engine. Then clutches are necessary. Cruise ship now nearly all use diesel-electric coupling to the screws.

 

[marcusl]

Actor/racer Tommy Ivo was the first to go 8 seconds, and break 180, in the quarter mile. He used the twin-engined dragster shown in this photo gallery
http://twotogo.homestead.com/TommyIvo.html"

That site also documents twin-engined dragsters going back to 1949. Most twins cars used inline engines with connected cranks. Ivo put his engines side-by-side, meshing the two flywheels together, but taking power off of just one crankshaft. The left engine turned backwards, so it needed a custom mirrored camshaft and magneto.

Here's a demonstration that makes it look easy
http://www.youtube.com/watch?v=gXCl_KKbIt4"
Ivo later built and raced a four-engine dragster, too.

Older readers with more interest in memories than mechanics might prefer this picture of Ivo with Mouseketeer and fellow beach movie star Annette Funicello
http://www.tommyivo.com/Cars/TheBarnstormer/tabid/488/Default.aspx"

 

[Ranger Mike]

TV Tommy Ivo was a trail blazer as was Mickey Thompson.

The Freight Train was one of the most successful dual engine efforts in the 1960s. this top Gas Dragster was running 7.3 e.t. well ahead of the competition. It used two small block Chevies. The basic problem of multi engine design is weight vs. horsepower gains vs. traction available with the tires.

 

[Lsos]

I’ve been searching high and low for an answer to this question. What actually HAPPENS if two engines were to power one drive shaft? I heard back in the days that cars were built this way to break speed records, and I heard present day it is used in tractors, but what increase.

My question is what is affected HP, torque, acceleration, what are the advantage of connecting multiple engines together?

Saying if they are the same make model, connected properly, and synchronized, you know all the rudimentary stuff.

The advantages are the obvious power gains. If you couple two identical engines together you should essentially have 2x the power/ torque. Yeah there will be losses in transmissions but one engine also has losses. You might get into packaging issues that might affect efficiency but that's another story.

The disadvantages are pretty obvious: extra weight, complexity, cost, and obviously, you somehow have to shove a second engine in there.

People seem to think that there's issues with synchronization. They will self-synchronzie if they are mechanically attached to the same shaft. If one wants to spin faster than the other then that's too bad: it won't. It will have to speed up the second motor with it.

It's no different than synchronizing the wheels and the engine. You just mechanically connect them and it's all going to spin at the same speed/ ratio (unless something broke).

 

[Ranger Mike]

My question is what is affected HP, torque, acceleration, what are the advantage of connecting multiple engines together?
advantage///none now a days...
you can amp up just about any single engine to fry the tires available today with modifications..i read some where.. and can not source this..that 800 hp is limit of "useable h.p. " for any street tire combination..

 

[xxChrisxx]

Back in the day people used to connect engines together all the time, especially when they had separate blocks and crank cases. Two I4's into and I8, two I4 into a V8. Etc. These are fully coupled engines that put the pistons on the same crankshaft.

U engines use two I engines with separate crankshafts geared together into a single output.

Fundamentally there isn't anything complicated going on, you are just connecting more single cylinders as stuck on zero said.

 

[HowlerMonkey]

DB610 engine used a common crankcase for two db605 engines with a gear drive linking both of the crankshafts to a common output shaft.

Alfa Romeo Bimotore.

The "pogo" used two engines linked by a gearbox called the allison t40.

Bugatti P100 racer...who's image is linked because of it's size.

http://sobchak.files.wordpress.com/2009/11/bugatti100cut.jpg

Fiat engine...a true engineering masterpiece in that the engines were run "back to back" among onther brilliant ideas.

as used in the airplane that still holds the record for fastest piston engine seaplane...and most other piston engine planes save for a few.


[PLAIN]http://upload.wikimedia.org/wikipedia/en/c/cf/Macchi_M.C.72.jpg