crank blocking

[not2bright]

on nitro motors can you put a plastic block on the opisite side of the crank so there is more velicitly in the crankcase in theroy more performance ???

 

[TimD]

If you mean reducing the case volume then that is an interesting debate. Some experts say it is vital while others dissagree. Having seen inside the Nova long strokes and the increase in case volume, I'd say it isn't as critical as some people say, but I'm no expert.

 

[Ian Inverarity]

Not2bright,

I would not get to worried about crank case volume with modern piped 2 strokes. I think you would find almost no benefit from 'stuffing' the crank, and if the 'stuffing' comes out you can damage the motor. This has happened to me with factory stuffing... >

Ian.

 

[TimD]

Hey Ian,

I think we had this conversation a few days ago over a few!!!

Did Gruber tell you I couldn't get a parking spot the other night so I dropped him and Ozzy off at the door and left - sorry I didn't make it back to finish the conversation......

Still OK to send the carb and rotor housing???? I have a lot of work to do before the ACT titles in March....

 

[Ian Inverarity]

Tim,

Yeah, I recall discussing it! 8)

Nah, Gruber was ticking along pretty well by the time I saw him next so I think he forgot! :

Yeah, send it along. My booms are all here too, I have heaps of work to do to get both boats going again. :-

Ian.

 

[Twin_k90]

Ian ,

i have asked hammer if he still has that other 9B that was all stuck up, we can fix it and put it on your K90,

glad the booms arrived, that humming bird is seriously fast and will need them i think, im going to fit the glass booms back to the twin as well now i have fixed the diving problem, i think i worked out the slowing in the turn problems, i think it is related to the turn fin position against the CG, lighter booms will help that,

Dale

 

[GTR]

Hi Guy's

Crankcase stuffing is a much debated subjecy as TimD has said. McCoy used to make full circle cranks for K&B a few years back. While it may provide a benefit on motors that do not rev in the regions we are used to I have serious doubts about how much effect it can have at say 30-40k. Part of the problem with this is that it causes port shrouding on front induction rear exhaust motors in particular. Can probably be of some benefit on rotary disc or direct piston port designs though.

I'm not expert enough to reaqlly know and it sounds like aq lot of trouble for a 'possible' little extra benefit. Making what we have now work more efficiently would probably achieve more.

My $0.02

GT ;D

 

[Ian Inverarity]

Dale,

The 9B would be nice I think, make it easier for me to drive on the throttle for the conditions.

I reckon the problem I had in the last heat with the K-90 was related to it eating the flywheel collet and killing the bearings. With the amount of brass I got out of it I am surprised it kept running! I will check the collets better next time! :-[

I am going to change the boom fixing method a bit, I discussed it with Eric A and he had some good suggestions.

To the best of my knowledge, the fore and aft position of the turn fin affects the ease of turning, ie how much rudder is needed. The John Finch book discussed this, but I dont remmember and my book was stolen... > I am guessing, but thinking about the physics of the situation I would say a fin that is further forward would require less rudder input (and thus less drag from the rudder) but would also be more prone to spinning out or hooking into a turn.

Ian.