Model aircraft engines for bikes?

buzbikebklyn1

buzbikebklyn1

New Member
I just cracked my second china girl 66cc crank case, while looking for replacements i came across this company-

HobbyKing Online R/C Hobby Store : Gas/Glow Engines & parts>Gas Engines

They advertise several 50cc singles and twin 100+ cc opposed twin cylinder 2 strokes(like a mini BMW opposed twin motorcycle engine) at reasonable prices, but seem to have no provision for a clutch housing of any kind... but the cases are cnc machined billet!
Its got me thinking of machining up a center-fugal clutch housing and mounts.
That opposed twin would be wicked!
Any one have any experience with this?
BBB
 
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Like the Tartan Twin?


Well, anything is possible - but generally they run crazy high RPMs and use exotic (read expensive) fuels....
 
Talk about needing a wider crank...Wow, you'd get bow legs riding that thing.
Generally speaking model airplane engines are not designed for loads of torque. They run short stokes and produce their power through their higher rpm. Barley Awake is also right about the fuel requirements. You could probably drive a giant SUV cheaper than what you could buy fuel for one of those engines. In fact, lots cheaper. The last gallon of 15%nitro fuel I bought was over $20.00. There are some of the giant scale planes using traditional weedwhacker, two stroke engines but unless you want to go friction drive and ride slow they aren't the powerhouse type we need either.
I have to question the quality of a couple of those engines too. Compared with the Japanese made Saito engines, these things are very inexpensive.
Not trying to be a wet blanket, Buz, and please let us know if you try this, but I think your money could be better spent on an engine designed for a heavier application.
Tom
 
2door said:
Talk about needing a wider crank...Wow, you'd get bow legs riding that thing.
Generally speaking model airplane engines are not designed for loads of torque. They run short stokes and produce their power through their higher rpm. Barley Awake is also right about the fuel requirements. You could probably drive a giant SUV cheaper than what you could buy fuel for one of those engines. In fact, lots cheaper. The last gallon of 15%nitro fuel I bought was over $20.00. There are some of the giant scale planes using traditional weedwhacker, two stroke engines but unless you want to go friction drive and ride slow they aren't the powerhouse type we need either.
I have to question the quality of a couple of those engines too. Compared with the Japanese made Saito engines, these things are very inexpensive.
Not trying to be a wet blanket, Buz, and please let us know if you try this, but I think your money could be better spent on an engine designed for a heavier application.
Tom
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2Door,

I thought airplane engines ran at too high of an RPM too, but check out this little guy. HobbyKing Online R/C Hobby Store : RCG 50cc Gas Engine 5.2HP/7500RPM - 5.2hp at 7500 rpm. If that's true, then this motor seems like a real option.

Erich
 
Erich,
They are also gasoline engines, not glow fuel. I'll admit, I've been away from R/C planes for a few years and not up on what is currently available. Maybe someone will give one of these puppies a try. The biggest hurdle I see is getting the power to the rear wheel. You'd need to devise a shaft drive, like 26incher suggested, and find a clutch that would work. Go for it, and keep us posted. :)
Tom
 
2door said:
Talk about needing a wider crank...Wow, you'd get bow legs riding that thing.
Generally speaking model airplane engines are not designed for loads of torque. They run short stokes and produce their power through their higher rpm. Barley Awake is also right about the fuel requirements. You could probably drive a giant SUV cheaper than what you could buy fuel for one of those engines. In fact, lots cheaper. The last gallon of 15%nitro fuel I bought was over $20.00. There are some of the giant scale planes using traditional weed whacker, two stroke engines but unless you want to go friction drive and ride slow they aren't the powerhouse type we need either.
I have to question the quality of a couple of those engines too. Compared with the Japanese made Saito engines, these things are very inexpensive.
Not trying to be a wet blanket, Buz, and please let us know if you try this, but I think your money could be better spent on an engine designed for a heavier application.



Point well taken 2door, they do seem like they might be short on torque.
I managed to get a hold of an RCG 50cc plane engine at my local hobby shop for measurement purposes.(really nice guys by the way)
After a session with a set of dial calipers and a mechanics ruler I found that size wise,this little beasty COULD be made to work with a shift kit type of arrangement, it would require machining down its out put shaft to the proper length and cutting a key way in it or threading it for a chainsaw centrifugal clutch.
The four large mounting "ears" would lend themselves readily to a plate type mount that can easily be adapted to the jack shaft/seat post plate.
As for exotic fuels the guys at the store say good old premium gas mixed at 30:1 is all you need.
As far as extra wide cranks for that boxer engine? how about mounting that boxer twin longitudinally along the frames down tube? It might require a longer primary chain but it could work.(plus it would just be plain old cool!)
I think i might just have found an alternative to those ridiculously expensive Morini motors.
Ill keep ya posted.
BBB
:-||
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At that price ($204.65 each plus shipping) I could buy 2 of them with shipping cheaper than one Morini S6S.
At the weight of 1360g, its lighter than a Morini, figure on adding another 3 to 5 pounds for the clutch housing and mounts, the mounts and clutch will weigh more than the engine!(using 1/4 inch 6061 aluminum plate, the thickest plate my little 110 volt Mig will weld)weight wise we have a winner.
Power and RPM wise 5.2 HP@ 7500 rpm sounds pretty good to me. They do not list torque figures, but present that value as "thrust"-
Thrust: 13.6kg @ 100mtr / 11.5kg @ 1800mtr (Above sea level)Draw what information you can from that.
Upon closer examination I find these engines have almost no flywheels and tiny short throw cranks with no counterweights, I think it might not have the torque required to haul my fat behind from a stand still with out stalling/bogging.
Im looking for a used one to experiment on now.
Ill keep Posting.
BBB
 
Oh, but the sweet sound...Hmmmmm......maybe a Fly wheel/gear drive /clutch/drive shaft housing? using one of Rock solids shaft drive type arrangements?
Glo plug engines use exotic fuel... these are good old honest to blue smoke 2 strokes.
Perhaps mounted far forward in a low slung chopper type frame?
A very light weight 110 cc screamer that under weighs the lifan 110 cc 4 stroke? its worth a try.
I cant help think of the possibilities.
Mini beamers any one?
BBB
:-||

BarelyAWake said:
Like the Tartan Twin?


Well, anything is possible - but generally they run crazy high RPMs and use exotic (read expensive) fuels....
Click to expand...
 
Hey Buzz, can you tell us how the 2 crankcases got cracked? I'd like to know so maybe with extra care, I can avoid that problem.

Thanks, Wayne
 
Well Wayne, I use pirate cycles universal front mount with a SPB shift kit rear mount.
As near as I can figure the flexibility of the front mount wasn't compatable with the rigid rear mount and a few harsh landings is all it seems to take to crack the cheaply cast cases of your average china girl 66.
(I still say there cast from melted down beer cans)
I have since changed over to the SPB front mount for over sized frame tubes, yes the "U" bolt is ugly as sin,but it doesn't allow for any fore and aft movement of the engine, this requires you to make sure the engine is installed at the proper height and its chains adjusted BEFORE you tighten down the mounts for the last time and that tightening said mounts does not screw up the chain tension adjustments. I use nylock nuts on all my engine mount "U" bolts.
My ultimate fix will be a cradle plate that wraps under the entire engine and meets the front mount so the engine will be fully isolated from harsh jolts, this way the cases take little if any impact stress at all.
(I find old phone booth casings are a good source for 1/4 aluminum plate)
Finally... the culprit that started it all excessive VIBRATION!
this is what prompted me to use the rubber isolator front mount in the first place, yes it worked well Pirate makes some great parts, but its in nature of the china girl 66 to vibrate like crazy. I'm currently experimenting with other mounting methods for the entire drive system to aliveate at least some vibration.
The key alignment has to be between the drive chain off the jack shaft and the driven freewheel chain ring, this is critical, the motor can move in any other plane EXCEPT side to side.
I'm looking at the Harley Davidson rubber mount sportster for ideas (designed by Eric Buell!) If your gonna steal designs, steal from the best!
Hope that helped...
BBB
 
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Being an R/C flyer and converter of trimmer/ chainsaw engines for plane use, I can say the bulk of Chinese R/C engines have been somewhat problematic. They have had bearing and ignition issues. Not all but many. A great running and very easy engine to convert is a Homelite 46cc chainsaw(among others). The chainsaws have agressive port timing and make gobs of power for their displacement ( I imagine close to 5hp). The Homey comes out of the case like a big model engine ready for a beam mount. It also has a clutch. I have seen these saws for as little as $109 new, and have bought them at yard sales for $25. They also have a recoil that could be used. That would be somewhat of an issue with the R/C engine-starting it.
 
Cutquik® Cut-Off Machines Features - Cut-Off Saw Standard Features | STIHL

And its already got a clutched belt drive on it, unfortunately its more expensive than a Morini S6S.
My entire point of this thread was NOT to have to spend $600+ on a new engine.
(yes, I know they can be had cheaper)
I started with a 52cc McColloch chain saw WAAAY back when in the 70s when I motorized my first 10 speed,I even had a double split casset type rear freewheel,one for the engine and one for the bikes shimano drive train, but as you might figure the brakes and wheels of the era weren't up to that engine.
Chain saws might be a good source for alternate engines now though.
Good looking out.
Any other alternate engine sources guys?
BBB
"WE HAVE THE TECHNOLOGY"
 
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The old Yamaha kart engine might be worth looking at. They can be had pretty cheap used. They are fairly small and can easily get into the 15hp range. Chainsaws are just so easy to scrounge at good prices. A saw in the 55cc range would really rock and roll. Would be smoother than the 2 stroke bike engines also. The fact they have a clutch and an adaptable recoil is a plus also. The twin cylinder R/C engines would be cool. The easiest way to adapt one would be with a clutch set up like the EZ where the engine driver is fixed. Still have to come up with a starter arrangement. They also use electronic ignition which would require an onboard battery, but generally the drain is low to the point that that a small gel-cell would run it for hours.
 
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