Deep finned flywheel

[Norrie Bodge]

Guys
deep finned flywheel? Leave deep finned or get milled down to std sized?
It's already been lightened, but are they any cooling benefits from the deeper fins??

It's gonna be used on a resleeved TS1-225 motor

Cheers

[rossclark]

I'd keep the deep fins, the Indians did that for a reason.

[gaz_powell]

Leave it long!!!!

[Knowledge]

I agree. I am fitting (hopefully) an engine with 40% more cc's, there is likely to be 40% more heat (at least) so I got a virgin deep finned flywheel from Corrado which I have machine down to 2080g, but left the fins intact.

I will be fitting a deep flywheel cover, carefully fettled so the cowling is 1mm off the ends of the fins, in order to eliminate cavitation.

I need to work on a system to help me re-balance the flywheel now I have take so much metal off it

[dickie]

In my first job (before I was even an apprentice!), I used to balance impellers for big industrial fans. The process was.....

Mount the impeller on a shaft mounted between 2 pairs of bearings.

Spin it slowly and let it settle so that the heavy point stops at the bottom.

Stick a lump of plasticine opposite that point and adjust weight of plasticine until the impeller has no heavy point.

Weigh the plasticine then rivet a lump of flat bar of the same weight where the plasticine was.

Now clearly we can't rivet a lump of steel on our flywheels. But you could do the same but drill metal out of the weight of the plasticine from the heavy point.


I'm not saying it's perfect technique but it might provide food for thought.

[Wack]

Years ago I used to balance turbo impellers on a balancing machine using the same plastercene method then ground the heavy side. For doing flywheels now ,I machined a bar with a crank taper half way down then use a crank truing jig to spin the flywheel and find the heavy point and drill holes in the flywheel rim until true. How accurate this method is I'm not sure but seems to work.

[dscscotty]

the length of the fins won't matter, as long s cowlings are compatible, and space between fins is minimal. Team Casa group 6 race scooters ran reduced fan blade height with no issues,

[HxPaul]

I always thought that the Indians made longer finned flywheels because they thought that it would aid cooling,but that idea had been checked out and it was found that the longer fins made no difference to cooling.

[Knowledge]

Paul,

Is that a statement based on information you have uncovered other than Scotty's post earlier?

I ask because the Casa engines run in a very specialised environment compared to a road scooter, and i wondered just how much evidence there was supporting "big fins doesn't mean more cooling"

[HxPaul]

http://www.mbdevelopments.co.uk/lambretta/lt17.html If you read this article and scroll down to-Indian electronic ignition-It has a passage in it refering to the long finned flywheel.

[Norrie Bodge]

Thanks for all the replies!

By reading some replies & your link Paul it's get it machined down then? But do I??
Also does anyone do a TS1 cylinder cowling to match the deeper finned flywheel?? If I decide on keeping as it is?

Cheers

[Warkton Tornado No.1]

Post by Norrie Bodge » Mon Oct 17, 2016 12:34 pm

Thanks for all the replies!

By reading some replies & your link Paul it's get it machined down then? But do I??
Also does anyone do a TS1 cylinder cowling to match the deeper finned flywheel?? If I decide on keeping as it is?

Cheers

I’ve read this thread with interest & my initial comment does concern ‘proof’ as that is the only thing lacking from all of the contributors. That includes me, so I’m not aiming to cause any offence

However, despite what anybody may have said thus far, including any technical articles by ‘Gurus’ (if that is the correct term....) there has been some research by kit manufacturers concerning the efficiency of their fans, but I do not have it to hand to reproduce here.

On the issue of balance, if good static balance can be achieved via the methods suggested, my own belief is that dynamically, the likelihood is that the flywheel will probably be as good, if not better, than the unmodified standard product.

As far as the running fit, the clearance to the fins should be as close as practicable to eliminate cavitation. In the case of the AF lightweight electronic/J/Luna flywheels, a ‘top hat’ plate would seem to offer the ideal solution fitted inside the original flywheel cover, but an annular ring fitted close to the fins inner diameter would seem to suffice.

Having said that, my belief is that there will be a lot large frame motors running around with small frame flywheel fans fitted with no cowling modifications. It would appear that if my assumption is correct, those motors may have no issues concerning cooling.

That leads me to believe that the Indian modification may be something they found necessary due to their riding style & climate. The chances are that with the Indian home market, users are much more consumed with the importance of economy & may well labour their engines significantly with a combination of questionable fuel/oil quality, climate, load & plodding in higher gears than they should.

It’s not so long ago that the AF lightweight flywheel was the almost universal fit in racing, the alternative being V*spa electronics fitted with plastic fans. Latterly, those P#agg#o auto fans were fairly bombproof compared to the fragile electric motor type.

If you’ve read this far, what I would conclude is that the standard fan type, fitted in an all around good assembly, is more than adequate for the majority of the engines built for the large frame Lambretta.