Engines in tandem?

[desotoman]

When you couple two motors together, what is the best way for torque and HP? In otherwords if you had two 8 cylinder motors, would it be better to fire them as an 8 cylinder or a 16 cylinder? What are the gains vs. losses of running them different ways? Which way would be better for torque? I was once told that when you add a second motor, you only pick up 50% of its power overall. So if you had two 300 hp motors and you coupled them together you would only get 450 hp on a dyno. Any truth to this. I am sure the bike liner guys know the answer to this. Thanks for any help. Regards, Tom Gerardi

[RichFox]

If you are right about power loss when coupling engines together, Union Pacific has had it wrong for years.  RF

[JackD]

Power is just like weight. The scale only knows how much the total is.
Unless you have built in a delivery method that takes up power, the finished product will never know the difference.
Imagine a big guy and a little guy both pushing the same car as hard as they can. Who is doing the most work and who is going to get there first?
It goes without saying, but i am going to say it anyway. LOL
The coupler has to be strong enough, and the point of attachment, all the way to the delivery point strong enough to last. Most of the crank failures are as the result of moving around with power to the point the bearings will not maintain the separation and cooling provided by the oil.
That is all pretty standard stuff. What is not said is the timing between the motors. Each will have it's own power delivery characteristics and are independent of each other. What is important to the smooth transmission of the power is how they are timed between them. It is common practice to build a couple of degrees into the coupler so the front motor always happens just enough ahead of the 2nd to always load the coupler.
Long ago, 2 motored bikes would build a couple of degrees advance into what was otherwise identical motors. When setting the idle, they would make sure the top run of the chain was always tight.

[desotoman]

Hi Jack,
    Back around 1985 I was helping my friend run his lakester at El Mirage. I was talking to the guy in front of us in line who was running a twin engine Harley liner and the motors were coupled together. I asked him if it mattered if they ran the motors as one big twin or as a four cylinder. I believe his reply was that running it as a big twin increased the torque output. But I believe he told me that horsepower was the same in either configuration, in which the second motor only added 50% of its horsepower.  Just trying to find out if anyone else has done dyno tests like this and what the results were. Regards, Tom

[JackD]

Their are 2 HD liners built since the mid 70s with twin motors and neither ever ran El Mirage.
You are likely talking about Leo Hess who was running the old Bob George/ Dave Campos open twin. All 3 bikes were built by Bob.
You either misunderstood Leo or he was wrong.
The cranks were linked and the timing between them was as I described if he knew it or not.
Since then 2 open bikes and 2 liners (2 Suzis and 2 Kawis) have been built that link the output shafts without regard to timing the motors between them. The harmonics between them are dampened by the path taken in the gearboxes and clutches.

[desotoman]

Hi Jack,
   The conversation was 20 years ago. I could have misunderstood what they were saying. That is why I posted. Thanks for your help. Regards, Tom

[Seldom Seen Slim]

Bob Moreland's Spkye bike at Bonneville has a pair of Harley engines - and has made a number of passes.  I don't know how those engines are tied together.

There's a guy that runs both Maxton and Bville -- he's got a pair of Harley engines in his bike.  I don't know how he keeps 'em together.

Tom Metty has so doggone many variations on a bike that he may well have a two-engine Harley going.

There -- three multi-engine bikes for you to chase down to see if you can get anything from the builders.

And then there's Dan Wright's streamliner under construction.  He's got a pair of Suzuki bike engines, but I don't think they're linked by anything -- or, if they are, it's a fly-by-wire link.

I don't have any data for you -- just some suggestions of folks that might be able to provide clues to your quest.

[desotoman]

Hi Jon,
   Thanks for the information. I will try and contact one of the people you mentioned. Thanks again. Regards, Tom

[Dakin Engineering]

Yup, Tom has a twin engine Harley. Think he calls it "the Ugly". Or the Good. or the Bad. Look for him at Speedweek. Got an addy somewhere if ya want.

[hawkwind]

My forever sidecar streamliner cause its going to take forever to finish , has 2 Kawasaki motors side by side but offset to minimise the width,it uses both gearboxes which drive through a common jackshaft to the rear wheel ,gearchanges are coupled together and activated by air . Iwill be running them as an 8 cylinder with one ecu , don't know if this has been tried before ? but it was the easiest way for me to run 2 motors ,caveat they have not been run yet or for that matter fired up so its unknown if it will work
Gary

[1212FBGS]

Zotoman
Well there are only a few of us that actually run or have ran multi engine vehicles I can give ya my wisdom  “Don’t do it!” It’s double the budget, double the parts, double trouble, double fun and double the pain in the Acura. Dolan has built and raced doubles but he really enjoys double talk and riddles. I really think he enjoys seeing people foolish enough to try it. You are correct double engines are only 75% total increase in hp but doubles torque. After all torque is what pulls 3 mile long trains, torque is what pulls stumps, and torque is what pulls heavy streamliners with moon gearing to record speeds. Since my liner is only 27” wide it is too wide to fit onto my bike dyno and is too narrow to fit any car dyno rollers I have found yet. So exact numbers still elude me. My motors put out 360hp and 165tq in a bike chassis each. So I figure I have bout 500hp and 325tq to the rear wheels. That’s small block Chevy numbers. That’s why we had to have billet trans made cuz we were ripping them out of the cases. Than we were just ripping the motor mounts off the motors, now we just snap drive chains like shoe laces. But were getting there. Soon well have all the bugs worked out (Dodge wet salt)
As for your question bout 8 or 16 cylinders, 8’s fire at 45 intervals to clock another to fire at 22.5 would be possible but not really necessary. Spend your time figuring out how to make a bulletproof flexible coupler that will handle 1500 lbs of torque that wont break the cranks. I couple my motors through the output shafts. the motors sync through harmonics. It’s like a tuning fork, when these babies sing its sweeeet. I currently own that Bob George liner you saw on the dirt. It was coupled through the crank primaries. Last year Bob Mooreland and the easy rider liner’s crew chief Keith Ruxton, spent a lot of time with crank leed and timing Bobs motors. I know what there crank phase is but cant say its kind of there secret. Don Vesco’s double bike liners always had the trans cut off of the front motors and linked crank to crank. Don always had chain or belt problems due to crank speed. The Rick Vesco twin Yamaha engine liner I own has both motors coupled to the output shafts cuz the cranks run twin blowers. The Ack attach liner is coupled at the rear wheel. The front motor uses a jackshaft to transfer drive to the right side and then back to the rear wheel with a chain. The rear motor is direct to the rear wheel. Metty’s bike is crank to crank just like all Harleys and Max Lamby’s Vincent is crank to crank via come pretty awesome gear drives. Probably the best coupling I’ve ever seen. All the double Harleys, the Vincent, and Vesco’s liners ran one trans and all have had major trans problems. All these bikes double the HP and TQ but run it through ONE trans that gives it up. I run 2 trans to half the torque loads, after a few motors and a few grand we finally have the trans worked out. I also run 2 complete systems. 2 motors, 2 ignitions, 2 ecu’s, 2 turbo's, 2 waist gates. I tried linking the turbo's once, when I lost a valve in the rear motor it took out the front and rear turbo. I changed that crap right back to 2 separate systems. I have no problems shifting both motors, Jimmy Odem had a shifting problem with the linked system on the Ack liner once, but I think they straightened it out as Noonan has yet to have a repeat of the miss shifting. If your thinking strongly about car motors you should talk to Rick Vesco about Dons experiences with the twin Offy’s or Rick White about the twin Hemi’s in his dad’s 400mph liner.
Man I gotta stop now, I can go on and on ‘bout doubles but both of my typing fingers are getting tired. Maybe all this typing ‘bout double engines will get me double points!

[1212FBGS]

Man what a rip, I only got 17.7 points for that post and it took me 2 hours to type. Come on little A, give me at least a 1000 points and i'll teach dolan how to use the spell check
kr

[John Noonan]

Man what a rip, I only got 17.7 points for that post and it took me 2 hours to type. Come on little A, give me at least a 1000 points and i'll teach dolan how to use the spell check
kr

Duelan misspels on porpoise..

[JackD]

Come back to earth.
The test bike you were with in 1984 was a 2 engined, 2 trans machine built to test shifting and tires. It was built in 1979 to establish the methods to link 2 engines. After that Don built the 2 engined 6cyl Kawi that ran in late 79. Charlie Toy has it now in Arizona the last I heard. Nolan never ran a hemi anything. Always a BBC in that liner.
How do you explain the loss you are dreaming up ?
Have you ever seen a 16V-92 ? Don't tell them they have a loss. The Offys and the 2 SBC in Don's last car suffered from the same problem and it wasn't coupling. The Chebys for example riped on Vic's dyno but you put them in the car and they layed down with a super hot inlet temp that killed the HP.
If coupling engines kills so much power, how do you explain the Yamama TZ series ? Each jug is a separate motor.
"Riddles are mostly to make you think but they don't always work."
Try again.

[John Noonan]

Come back to earth.
The test bike you were with in 1984 was a 2 engined, 2 trans machine built to test shifting and tires. It was built in 1979 to establish the methods to link 2 engines. After that Don built the 2 engined 6cyl Kawi that ran in late 79. Charlie Toy has it now in Arizona the last I heard. Nolan never ran a hemi anything. Always a BBC in that liner.
How do you explain the loss you are dreaming up ?
Have you ever seen a 16V-92 ? Don't tell them they have a loss. The Offys and the 2 SBC in Don's last car suffered from the same problem and it wasn't coupling. The Chebys for example riped on Vic's dyno but you put them in the car and they layed down with a super hot inlet temp that killed the HP.
If coupling engines kills so much power, how do you explain the Yamama TZ series ? Each jug is a separate motor.
"Riddles are mostly to make you think but they don't always work."
Try again

There he is again Kent, puttin you and some points down...  Good thing he never shows up at a meet...good for you or him?