Jadewombat wrote: ↑
Mon May 18, 2020 5:48 pm
Interesting brewsy, but again (as I mentioned above) if you're in the lofty rev. range of 6,000-10,000 rpms and fan slippage is critical--why would you not run a toothed belt? I didn't see any mention of that in the article you posted.
Blowers run toothed belts for that reason. The faster you turn something the less it wants to turn.
I think Bruce has hit the nail on the head.
The stock fan has a limit to the RPM it can take without modification (welding the fins) BUT there isnt much point in revving it higher as the maths show that a) it takes poop loads of power (hahahah STF has spellchecked what I actually wrote - Id never use 'poop
') to spin it faster and b) it doesnt end up pushing much more air beyond a certain point.
So Bruce's analogy of a clutch is perfect and it 'slips' when the fan trys to draw too much HP.
As I understand it most high rpm folk are concerned about the fan belt coming off rather than actually trying to push more air through the engine.
So in that case a belt tensioner/guide thingy is probably better as it will keep the belt on the pulleys but the 'clutch' will still slip when it has to.
Besides which if youre making a high HP engine and are doing everything to squeeze every last drop of power out of the old 2V AC engine why would you want to use up (lots of) precious HP spinning a fan when its not achieving anything?
There is a guy in the UK who has engineered an AC type clutch onto his generator assembly as he has a super high engine RPM combination. Before a run he engages the clutch to 'stop' the fan, does a 1/4 and then in the return lane engages the generator/fan again...
The belt stays on the pulleys as its not transferring any torque and slipping and for the 20-30 seconds of the run engine temps are within control.