cable collet ?

[ernest2]

hi!

is it possible to use Prather Cable Collet K+B 7.5 3/16 for an O.S. .21 RG-M engines? i'm planning to buy this engine thru tower and it's the only cable collet avail there. i'm ordering from overseas so shipping cost is very critical if i order through different stores. thanks!!

and one more thing, is this engine good for sport run?

ernest

 

[anthony_marquart]

I'm pretty sure that you will need a different collet. COuld be wrong but I wouldn't bet on it.

The OS rgm is a good sport engine.

 

[Eric Perez]

I have this exact Prather collet in my tool box. I will try it myself on my .21 engine with 1/4-20 threads (Which I believe is the same as the OS.)

I'll give it a try when I get home tonight.

 

[longballlumber]

I would suspect that any collets with 1/4-20 threads will work. However, a lot of variables will come into play.

Are you using the OS flywheel? If so, you may need to remove some material from the flywheel in order to get enough tool clearance for the collet. (Or you can put a spacer between the flywheel and the collet).

This has been my experience with an OS RZ-M, an OS flywheel, and an aeromarine collet assembly (which was labeled for an OPS)

Hopes this helps.

 

[ernest2]

the os engine comes with the os flywheel.. yes it has a 1/4-thread. but my concern is that the collet and the flywheel might touch or would not fit. thanks!

ernest

 

[Kez]

Ernest2,

I believe both the K&B and the OS RG-M have 1/4-28 thread so that is not a problem.

However, the collet for K&B has a 'shoulder' machined into the end so that it fits into the recess of the K&B flywheel. If the flywheel of the OS does not have the same recess, then you would need machine work to make them fit.

On a seperate note, I have found that most collets have a runout more than I would like (0.010"). I had to buy three collets to get one that runs true.

Kez

 

[Mike Hughes]

If the flywheel of the OS does not have the same recess, then you would need machine work to make them fit.

Don't machine the flywheel, just grind off the shoulder. Much simpler and cheaper to boot.

Mike

 

[ernest2]

thanks! i've asked prather about this and they say it would fit but i might need a washer in between the flywheel and the collet. frankly i don't have any idea because it will be my first engine and drive hardware ... thanks for all the infos guys!

ernest

 

[Mike Hughes]

Yeah the washer will work also. You will see when it shows up. Pretty simple.

Mike

 

[GTR]

Hi Guys

Having an OS RG-M I can tell you the problem getting a collet to fit is the depth that it must go in to the OS flywheel. With a lot of collets there is only a small hex at the base and on the OS this is completely inside the flywheel making tightening a challenge. Haven't tried an aermarine collet but I think they are long enough in the hex to fit and am pretty sure the K&B 45 one will also. Just do the washer thing, grind of the hub, or machine a little recess. All should give a good result but I don't think a washer will fit in the flywheel recess unless you get a couple of K&B 21 washers. They use a washer under the coupling and could work - I would have to check the dimensions for you.

Ernest - where are you overseas?

 

[Eric Perez]

Here is the 7.5 K&B style collet that is sold by prather.

The picture shows that the prather 1/4-20 "flex-hex" or collet will fit even the OS .12 flywheel. I would have a hard time believing that the .21 flywheel would have a smaller opening than the .12 flywheel.

These are the tech details on the #2E for the .21 RG Marine engine and the #1D used on .12 engines. Note that both engines have a 15/16 OD on the front of the flywheel. I'm measuring the #1D flywheel that I have and the front ID is 3/4".

This is the O.S. Max Marine Flywheel #2E.

FEATURES: Precision machined for superior balance.

This helps the engine idle.

Has a groove in the middle for attachment to a starter belt.

Made of lightweight aluminum for quick acceleration.

SPECS:

Flywheel: 32mm(1 1/4") o.d. at rear tapers to 24mm(15/16") o.d. at front

13mm(1/2")i.d. 25mm(1") distance front to back

Steel collet: 6mm(1/4") i.d. 13mm(1/2") long

INCLUDES: One Flywheel (has 2 holes for rod to loosen flywheel from engine)

One Steel rod (about 2" long, 1/8"(3.5mm) diameter)

One Tapered collet (fits inside flywheel in front of engine bearing)

COMMENTS: Fits .21EX-M, .21RX-M

This press fit to the crankshaft (there are no threads).

This is the O.S. Max Marine Flywheel #1D.

FEATURES: Precision machined for superior balance.

This helps the engine idle.

Has a groove in the middle for attachment to a starter belt.

Made of metal. (It appears to be chrome plated brass since it is

heavier than aluminum and not magnetic).

SPECS: 29mm(1 5/32") o.d. at rear tapers to 25mm(15/16") o.d. at front

shaft size: 5mm i.d. 17mm(25/32") distance front to back

INCLUDES: One Flywheel (has 2 holes for rod to loosen flywheel from engine)

One Steel rod (about 2" long, 1/8"(3.5mm) diameter)

COMMENTS: Fits .12CZ-M, .12CZ-MX, .10FP-M, .10FP-MX.

This press fits to the crankshaft (there are no threads).

AXY 8/2

 

[GTR]

Hi Eric

Really good info but what I was talking about was the depth of the recess not the diameter. As you will notice from your pictures posted the 21 recess is a lot deeper and that is what causes the problem where you cannot get a hold of the flex. The flywheel tightening/holding rod is 4mm by the way.

 

[ernest2]

GTR i'm from philippines. i think that base on the pic eric gave, the prather collet fits just fine. but thats for the smaller engine though. how bout on the .21 rg-m flywheel eric, does it fit the same?

ernest

 

[Eric Perez]

I think the depth is going to be the issue -if any. I've had this problem before, not much you can do. Either add a small 1/4 spacer (If you have enough engine threads exposed) or you cut of part or (all) of the front shoulder off the flywheel like Mike suggested.

Either way you can make it work.

 

[GTR]

Hi Guys

Updated info straight off my OS RG-M The flywheel recess at the front is 3/8th(9.5mm) deep and 21/32nds(16.8mm) wide. The collet you pictured looks like it would still work but I can guarrantee an Octura one won't.