How to determine if crankshaft will fit existing clutch?

[pjoseph]

I am trying to figure out if the O S 18TM crank will fit in my existing setup on my hpi bullet mt. Not trying to fit the crank in my existing engine just clutch ect....
Link to crank: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHKV4

Link to current crankshaft
http://www.hpiracing.com/en/part/15146



Thanks

 

[Alexander_0_1]

The O.S 18TM crank is an IPS (integrated pilot shaft) crankshaft, and the one you have is an S.G crankshaft. As long as the outer diameter is the same as you current crankshaft you should be fine.

If your unaware, your current driveshafts front bearing measures out at 7X19X6mm.
the O.S 18TM also has these measurements. Outer Diameter: 19mm, Inner Diameter: 7mm, Thickness: 6mm.


Crankshaft types
There are several different types of crankshafts in use on nitro engines. The type required is determined by the model it will be used in.

Threaded crankshafts are the most common for small block engines. The part of the crankshaft that sticks out the front of the engine is fully threaded, except for a larger short smooth portion at the beginning where the flywheel goes. The RC model includes some type of clutch adapter. There are short cranks, long cranks, and in some cases the crank has to be cut, because the crank is too long for the clutch adapter to fit properly. The clutch adapter gives a method to attach a clutch bell to it, and are mostly smooth for the clutch bearings to ride on. They also serve as a nut to hold the flywheel on. You can cut these crankshafts if they are too long for your vehicle. You need to put the engine in a plastic bag, shove the crankshaft through the bag, put a nut on the crankshaft, and dremel the crankshaft. Use the nut to clean up the threads when you take it off. The bag will prevent debris from entering the engine.

SG crankshaft
SG crank is the most common for racing engines. The name, SG, comes from Italian race engine manufacturer SG that introduced the crank. This type of crank is mostly smooth, with a small threaded portion in the middle for a nut to hold the flywheel on, and a larger portion where the flywheel goes. They have a small threaded hole at the end, to put a screw, usually 3mm, in, to hold the clutch bell on.

IPS (Integrated Pilot Shaft) crank is a less common crank, mostly used on Traxxas vehicles. This is basically the same as an SG crank, but has an e-clip slot on the end to hold the clutch bell on, but they still have the threaded hole. This introduces the ease of changing a clutch bell thats held on a clip, and the ease of loosing an e-clip trying to take it off/put it on. It is a good idea to use a screw and a number of shims with the IPS cranks. If you do not want to use the method of shimming, you should at least run a screw in addition to the clip, just as a back up.

 

[Alexander_0_1]

I am unclear if the clutch bearing are the same size on the O.S18TM. I did however find this: http://www.hpiracing.com/en/part/b021

^I think this is your CB bearing size.^

 

[pjoseph]

Thanks for the reply appreciate it.

I'm a little confused it sounded like in your first reply that the crank shafts were the same size but now in your second post it sounds like they may not be?

Also where do those bearings go that u linked?

Still new at all this thanks again for your help

 

[Alexander_0_1]

I've only had experience with BB engines, and to my knowledge all the CB bearing I've dealt with have an inner diameter of 5mm. If it helps the CB bearings in your bullet MT are the same as the ones in a savage.


The bearings slide into the clutch bell, and the whole assembly will slide onto the crankshaft.

^This is illustrated in you manual. If for whatever reason your bullet didn't come with one, here you go: http://www.hpiracing.com/en/instructions/107006

 

[Nitro4910]

5x10x4mm is the stock Bullet MT clutch bell bearings, which is the same size as Traxxas engines which the OS 18TM was made to be drop in for.

Your Flywheel & Clutch assembly should fit on the OS .18TM, it may need a little shimming, as some do but other then that it should fit.
You'll probably need a Traxxas flywheel nut, as I believe the they are different then the HPI SG 1/4-28 style nut type you original engine has.

I'm assuming the bearings he listed was for the crank's front bearing.

For bearings same yourself some coin & order them from AvidRC.com , most are $1 each & just as good as the ones in the HPI baggy.