.12 rigger engine

[Don Ferrette]

"Gary himself has a new one being modded by Rod Geraghty but he hasn't told me what it is yet. I have an idea but nothing for sure. He may not be happy about Glenn Quarles taking his record away! "

And Preston took all the A hydro records away from both of them! :lol: :lol: :lol: :lol:

 

[Eric Perez]

Here are the current SPECS for ROAR .12 engines

 

[tracerbob]

I was looking at the O.S. .12TR myself. But what do you do with the unthreaded part of the stub shaft sticking out of the end of the crank?

 

[Propjockey]

DREMEL!!

 

[Guest]

take the TR with the standard 5mm crankshaft and you do not need a Dremel

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXALM5&P=7

 

[tracerbob]

Ah yes....thats the ticket. Thanks for the link.

 

[wswatzell]

I've got an OS TR/PT waiting for me to finish my HH 12 rigger.

 

[Ron Olson]

Here's what I just got from Jeff and Troy Schroeder at Fantom on their rear exhaust motor:

'03 FR-12Rear Exhaust Port timing numbers;

Induction (hole in crank below carb hole) - Opens at 30* ABDC, Closes 55* ATDC = 205* Port Duration Period (total time in degrees of rotation that port is open).

Exhaust - Opens 79* BBDC, Closes 79* ABDC = 158* Duration

Boost - Opens 57* BBDC, Closes 57* ABDC = 114* Duration

Transfer (2 side ports on sleeve)

*Intake port to right of exhaust port - Opens 57* BBDC, Closes 57* ABDC = 114* Duration.

*Intake port to left of exhaust port Opens 59* BBDC, Closes 59* ABDC = 118* Duration.

Any help? What would the motor Guru's change?

 

[TimD]

What I'd probably do is look at raising the exhaust to 178, sleeve intakes to 128. Change the crank to closing at 65. Then have a good look at the head button shape and volume.

You might be able to get the timings on the sleeve up with a shim but depending on the taper of the liner that might not be the way to go and cutting the ports would be required.

The trick with the little motors is not to over prop them - they have to pull good RPM.

Tim.

 

[Terry Keeley]

"Gary himself has a new one being modded by Rod Geraghty but he hasn't told me what it is yet. I have an idea but nothing for sure. He may not be happy about Glenn Quarles taking his record away! "
And Preston took all the A hydro records away from both of them! :lol: :lol: :lol: :lol:

Word on the street is that Gary might have a new proto type Turbo Head to try on his Nova .12 this year

 

[Hammerhead]

Right now, I'm using an NR 5port. Max RPM 43500. It is a lot faster than the TR/PT that I used in the Last HH.12 that I had. The carb is harder to get right than the O.S though. As far as the Pilot shaft. WHACK IT OFF, use an O.S RZ .21 fly wheel, and 7mm to .150 joint from Aeromarine. Piece of cake if you have a disc sander.

 

[ClayGlover]

not sure about the TR, but on the Nova MT12 I have, the shafts can just be unscrewed from the crank. Mine was originally the "sg" car-type flywheel shaft. I just unscrewed it and used a cut-to-size black 5mm steel bolt (aka threaded rod) and screwed it back into the crank. voila, threaded shaft any length you want for about 25 cents.

 

[Watercadet]

Unfortunantly the OS' crank is not a universal type like the MT and must be cut. The regular TR can be ordered with a threaded shaft but the turbo version is sg only.

 

[TomMoorehouse]

Right now, I'm using an NR 5port. Max RPM 43500. It is a lot faster than the TR/PT that I used in the Last HH.12 that I had. The carb is harder to get right than the O.S though. As far as the Pilot shaft. WHACK IT OFF, use an O.S RZ .21 fly wheel, and 7mm to .150 joint from Aeromarine. Piece of cake if you have a disc sander.

exactly what one was it?

 

[ClayGlover]

here's the MT12 with slightly lightened OS brass/nickel plated flywheel and modified CMD mount. I've got a couple of P/S to play with, and I'll start just shy of Tim D's numbers. (Thanks Tim) It's a 3 port, so it should be pretty straight forward to mod.

This motor screams, and costs around US$150 to $160 with threaded shaft and rotary carb. I wouldn't go by all that HP, RPM, and number of ports that manufacturers claim. 3,5,7,9,11 ports? blahblahblah! Port size, angles, and timing is what counts. The NR 5 ports are supposed to be real quick, but to much $$$. I think with the right mods, this motor can be just as quick. maybe quicker

View attachment 1351

 

[TimD]

Clay,

No problem. B)

Those numbers are conservative but will work - the crank induction is the truly important one IMO. Do that 1st with stock induction timings in the sleeve and see how she goes. As we found with another engine (see the 90 engine thread) that induction ovelap is critical to low end and throttleablity. Best to creep up on it rather than cut a sleeve and then realise it's too far.

I'd be interested to try a HEAVIER flywheel on those .12's. The inertia and Centrifugal force would take a little longer to get to peak RPM but it would make it easier to launch and run more prop.

I'd love to hear someones feedback on this - I don't play with .12's in boats.

 

[ClayGlover]

i agree on the heavier flywheel idea, but i had to modify this one to get it to fit without hitting the carb. It's brass, so it's on the heavy side anyway. a lot heavier than it looks in the picture.

 

[TimD]

I see what you mean now you mention it B)

What fuel / head button volume you planning on running in that motor Clay?

 

[ClayGlover]

gosh, that's a new ball game I guess, I haven't even measured the stocker one yet. Any suggestions out there? i saw someone say that Pruesse might be making an aftermarket head for these small block NR's. Time to experiment I guess. B)

 

[Ron Olson]

I've got a small pile of them that I ought to take to work and weigh. By feel, one of the heaviest that I have seems to be one from ABC Hobbies for the Nitro Falcon. It kinda funky the way that it's drilled in the center, it wants to fit better on what I consider backwards with the groove close to the carb. My lightest seems to be one from a Miss Bud or else my modded one from CEN Racing. Hull style or weight could be a factor in figuring out what one to mount.