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Coupling Engines... Bad Idea? Talk To Me Boys, I'm A Man On The Edge...


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#1 bobbyrohr88 OFFLINE  

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Posted October 18, 2014 - 11:32 PM

Okie dokie... Guess I'll start off the the usual, "Hi, I'm Bobby... I love working my lawn tractors so much I try to blow at least one up a week..." *crowd* "Hiiiii Booooobbbbbb......"

Now that that's out the way, I have a 3 old tractors I've turned into pullers and a 2 I've made into racers... I'm fairly well versed in the small engine scene, I build all my own stuff and do all my own mods. But where I'm at now is I want something that makes people stop, look, and scratch their heads rather than give a passing glance and a 'Hey whats up' nod....

And I know how I want to do it------COUPLING ENGINES.

So here's my plan... I'm working with a '61 Wheel Horse 401 I've named Beyonce because of her big, fat, sexy back end with the duals on it. I'm reconfiguring the whole hood assy, and steering, so just pretend its non-exsistant as you're envisioning this...

Two engines...one in front of the other on the frame...each with matching #40 chain sprockets...timed 180 off of each other and chained together. Idler between the two, and the engine closest to the transaxle will have a pulley "outside" or "on top of" the sprocket to run the belt drive. I'll engineer an intake to accept a single (38mm? 40mm? Have to tinker around to find the right size I think) Mikuni carb equal distance from both ports.

Badda bing, badda boom...horsepower doubled, right? :/

Couple things I'm unsure of are whether or not I should combine the exhaust, leave pipe to it's own accord and run true dual exhaust, or use an H-pipe? Also, here's the biggy... The two engines I have done and ready to bolt on something are a 10hp Tecumseh and an 8hp Briggs. Both are HEAVILY ported and polished, literally as much and maybe a little more than should ever be done, both having as close to a mirror finish as you're gonna get. My train of thought here is those million dollar pro-pullers with a dozen V-8's on them... And you can't tell me every single one makes EXACTLY the same hp...So, technically, it shouldn't matter that the two are rated a little differently, right? Or will 'rotating mass' get me?

Whatcha think fellas... Is my math good or am I forgetting to carry a 1 somewhere??
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Posted October 19, 2014 - 12:24 AM

Welcome aboard.
Sounds like an interresting concept.

Back many years ago, I had a beater car that was a wonder of engineering. It was a Volvo 164.
6 cyl inline engine, twin carbs (one for the front 3 & one for the back 3), and plenty of get-n-go for the weight of the car. A little fine tuning on the carbs by someone who knew what they were doing and it was a good running engine... All that said, I always wondered why they didnt Y to a bigger carb.

If it were me and I was going to have my legs straddling something like this, I would tend to err on the side of caution and go with twin engines. The 20% difference right off the bat might be something to be wary of and would be more of a concern than a little difference in the plumbing length when it came to the intake.

As for the exhaust, if the engines are the same, then true duals... If they are different I would H them to blend.

#3 skyrydr2 OFFLINE  



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Posted October 19, 2014 - 04:48 AM

Welcome to the forum,
Your forgetting to carry the "1" and then dividing... Run them both separately and tune them individually then connect them together via a jack shaft. This is how the big guys do it. Then you can clutch each engine to pull in its power band. Good luck and we definitely would like pictures of your rigs ;-)
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#4 TomLGT195 OFFLINE  

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Posted October 19, 2014 - 05:57 AM

Welcome to GT Talk. Good luck with your project! Tom
Don't forget PICS!!

#5 baerpath OFFLINE  

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Posted October 19, 2014 - 06:35 AM

We used to have a WH in the club that ran two 10hp Kohlers. They were belted together so they could time themselves. and when they did they sounded good. The only thing I'd worry about would be the stroke on two different brands of engines. I 've seen a 16hp and a 10hp Kohlers hooked together also. And 6 briggs hooked up.  Most use the same brand of engine to match the stroke's

#6 JDBrian OFFLINE  


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Posted October 19, 2014 - 06:37 AM

If you try to run the power of both engines through 1 crankshaft on a single pulley you are going to have trouble, especially where both engines are already tuned for a lot more than stock HP. It will put mucho strain on the crank and bearing.

#7 LilysDad OFFLINE  


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Posted October 19, 2014 - 06:51 AM

I'm not sure about using one carb for two different engines. How do you tune that?

#8 Dieselcubmike OFFLINE  

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Posted October 19, 2014 - 03:56 PM

Theres a guy that pulls with us that has two 14hp kohlers that run together in a cub cadet.

#9 baerpath OFFLINE  

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Posted October 24, 2014 - 12:19 PM

Just saw this one Is this what you mean?
quad engine puller.jpg https://fbcdn-sphoto...179605ccdc019ac

#10 Leonard VanCamp OFFLINE  

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Posted October 24, 2014 - 09:57 PM

A couple of the guys brought up the main thing, two different engines with different power ratings. You look at any multi-engined pulling tractor you'll see all the same sized engine. And like somebody already pointed out they are linked via jackshafts, not to mention most pullers use torque converters to soak up some of the differences between the engines. Doing a direct connection will also mean major carnage if something lets loose in either engine, the other will either keep running or gernade also, meaning more chances of shrapnel flying around.

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