Flywheel advice

Should have mentioned that was PTO shaft rpm, belt pulley rpms were at least double that.

Tom

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Those with longish memories may remember my earlier postings concerning flywheels for a Ruston 1HR which I purchased from a well known fellow newsgroup member from deepest Oxfordshire.

The engine is ex-college and came with one spoked flywheel and an ugly solid brakewheel. Having removed the brake wheel, the engine was difficult to start on the single flywheel due to not having sufficient inerta to get over compression and running could have been smoother, so my search for a second compatible flywheel began. I was also prepared to use a single larger flywheel to produce a configuration as seen on many of the larger HR engines and also on the IP range of paraffin engines.

This morning, my pulse raced when I saw the ad for a 36" flywheel in the SEM small ads (p42) - the flywheel offered has a slightly larger bore than I need for the HR - 2.25" vs 2", but I guess that could be sleeved and a larger key made?

My main query concerns the fact that the wheel is not from an engine - it was on a 1950's era baler. Does anybody know what rotational speed this flywheel is likely to be rated for? The vendor does not know, but the photo in the advert suggests proportions similar to what we might expect of an engine flywheel, and not too far off a Ruston pattern.

Any thoughts? I'll be gong over to Somerset to take a look, but any information would be welcome.

Thanks..... John Ambler Sussex, UK Return E-mails to snipped-for-privacy@skiprat.net

John,

If its off a bailer I would assume that it would be for slow revolutions, structurally it could good enough for a relatively slow running engine. I think your inspection would be wise though.

Martin P

If it is dimensionally similar to the existing flywheel, in terms of rim and spoke section, and appears to be a decent casting I'd be petty happy to assume it was man enough for the job. You could always proof test it at, say, 2x running speed of course ;-)

A bit more information - the vendor said that the PTO of a tractor was belted to a 6" pulley on the baler.

Anybody know the PTO speed of a 1950's tractor? If its in the 500rpm region, this could indicate suitability for the Ruston - 5.5HP @

550rpm.

John Ambler Sussex, UK Return E-mails to snipped-for-privacy@skiprat.net

PTO's are 540RPM but if there's any doubt, you could shrink a steel tyre over the rim. Finish it well and once painted, no one will see it.

John

Just spinning it at the desired speed wouldn't test it effectively. It had to cope with the pulsating effect of being accelerated for a half rev, then provideing driving force for one and a half rev (on a 4 stroke), and the rapid change between therse two states. The strength of and number of spokes can be significant here. HOWEVER......the flywheel only really has to cope with the engine crankshaft/conrod/piston assembly mass and acceleration, and not the engine power unless a major stall occurs so does not have to be too beefy.

Al

John:

I seem to remember that the 1HR had quite small flywheels compared to the 1ZHR which we have. Would the Lister CS spoked flywheel be anywhere near what is required? We have a spare good flywheel with 2" bore in the workshop.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

Too big for a jiffy-bag though..... :-))

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

The 1HR has 24" flywheels with 2" bore, the 1ZHR are 34" with 2-5/8" bore.

The Lister CS flywheel is 23-3/4" diameter with 2" bore and 3-1/2" face, six spokes. There is a cast-in balance weight at the rim which is in the same angular position as the keyway.

Can't find any info as the the face width of the 1HR flywheel here, but I think it is relatively narrow by memory.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

If you go to look at the flywheel, take a hide mallet, or similar, and "tap" it in various places to see if it rings true. An old flywheel of uncertain history can be dangerous. Stress in flywheel spokes will double at 1.4 times a given speed and quadrouple at double rpm! So a steel tyre sounds a good idea.

Regards, Dave Carter.

I've been taxing my memory and hope I've worked this out right. The rim of the flywheel is travelling at 35mph and is subjected to 85g acceleration.

Better safe than sorry.

John

The spoked Ruston flywheel remaining on the engine has a face of

2.75".

The main problem I see with a Lister flywheel is the balance weight - what chance of removing it without causing damage?

Another problem with converting it back to a twin flywheel engine is that the crankshaft was shortened on the camshaft side, so with a flywheel fitted there is no space for a pulley to drive machinery - nor is there space on the "far" side for flywheel and pulley. With a single heavy flywheel configuration a pulley could be fitted to the camshaft side.

Thanks everybody for your comments.

John Ambler Sussex, UK Return E-mails to snipped-for-privacy@skiprat.net

Your figures stirred memories three decades old! Curiosity locked in and I eventually arrived at 52g. (tic)

(V x V / r ) / 9.81 (?)

ISTBC

Dave.

Bursting force in a flywheel is.....

0.000054WrN(squared) (that is N squared, not the whole thing)

where

W = weight of rim r = rad in feet N = RPM ================== max velocity for CI is 98ft/sec and for semi steel is 140

10 mph = 14.7 feet/sec

if your 35 mph rim speed is correct then you're running about half safe speed.

=============

to calculate energy stored you also need to know k, or radius of gyration

multiply this by 1.125 to include hub and rims

max twisting moment T = (bhp x 63000)/rpm in inch pounds

etc etc etc

I used VxVxR / G where V = angular velocity in radians per sec = 500 x 2 x (pi) / 60 =

52.36666 G = 32.2 ft per sec squared. (9.81 is m per sec squared).

so acc = 52.36666 x 52.36666 x 1 / 32.2 = 85.16G

Any other offers?

John

Thank you, gentlemen, I stand corrected.

Regards, Dave.