This supports and confirms the drift method described above.
All forces need to be applied to the flywheels and shaft only.
Even modest heat can assist any interference fit in dissimilar materials. This is a very common methodology. There are no drawbacks if competently done. Opening sealed glass jars relies on this phenomenon so literally anybody can do this.
Differential heating can assist when interference fitting of components made of the same material. A common example in railroading was fitting tires to wheels.
Interference fitting is very common, reliable and, by its nature, free of any clearance issues that might lead to alignment or vibration issues.
Another example of interference fitting in model locomotives is provided by drive gears which are just pressed onto axles. In most cases nowadays the drive gears are plastic pressed onto steel. Nothing allows the gear to drive the axle but static friction inside the joint.
Sure, we did it a lot in industrial environments. If you want to install a ring gear onto a diesel engine’s flywheel, sure heat is the correct way to do it.
On a model motor it is simply not a good idea and presents extra risks. It is irresponsible to suggest this as a good method.
It is obvious this is just theorizing and not based on actual experience.
There are too many small parts in a model motor that could be damaged by heat.
Be careful with your motors, take chances elsewhere.
Gentle heat for installing flywheels may make sense … e.g. putting them in a plastic bag in hot water. Use an IR spot thermometer to ensure you don’t get them hot enough to damage plastic motor parts via conduction – there is a large thermal mass in the flywheel, and only a small one in the shaft. Conversely you might chill down the motor-and-shaft assembly, which is the ‘other half’ of what’s normally done when making critical interference fits IRL equipment.
You could heat them with hot air, but it’s the temperature in the bore that is most significant, and I suspect keeping the heating properly ‘even’ until the flywheel has reached an equilibrium temperature might be tedious and long for the ‘benefit’ gained – you want good heat transfer from a controlled-heat source, which to me means liquid at a temperature low enough not to induce burns…
The press/vise approach is a good one, although I think I’d recommend that you have parallel (or articulated) jaws wide enough to keep from off-center pressure. I would be tempted to use washers of appropriate thickness (file slightly if desired and check square) if the shaft is to protrude through the end of the flywheel.
For a number of reasons I think brass instead of a steel drift would be a bad idea. Although I sympathize in principle with the idea of using a material that won’t ‘scratch’ the flywheel bore. I’d be tempted to consider using an undersize drift given a coat of good tough paint on its OD…
Not an uncommon problem with things I post. The concern I had was that a range of sources, some trustworthy, were advocating heat without being specific about how to do it, and while I agree it’s not really necessary for Genesis flywheels, more explanation than ‘heat bad’ might be useful to those wondering why people considered it.
Many easy ways to install them unbalanced, and bend shafts, too… Some of the advice in that NWSL handout, like drilling out the interference fit for part of the bore, seemed a little peculiar as advice to general hobbyists.
I personally think getting them off (with a proper method probably not involving heat) is less fiddly than getting them on – certainly needs less prep. You aren’t concerned either with balance or position in removal, only with not damaging the bore or shaft.
I’d agree in principle, certainly as anything less than a last resort for removal. This is not a structural interference fit that sees substantial torque or requires longitudinal keying to hold alignment on the shaft, so enhancing the clearance of the ‘fit’ as is done with the locomotive tires used in one cited example would be unnecessary.
I wonder if any use of anaerobic material or other adhesive on loose-fitting flywheels has been tried. If it has, then heat might be a more sensible ‘assist’ in removal. That strikes me as being firmly in the zebra category, though.
I would love to see how you are installing flywheels where this becomes a concern.
The flywheel (if you have a good one) is balanced from the factory. I know they do not use a dynamic balancer when they are manufactured, but the shaft hole is centered and the machining is symetrical, so they can be assumed as balanced.
There will be a slight press fit to get it onto the motor output shaft.
The only way to get it out of balance would be to either displace metal on the inside diameter of the flywheel or bend the motor shaft. Both of these would require considerable force and a willingness to ignore when something is obviously wrong and just force it through.
I have always used a nomal C-Clamp with homemade mandrels to install flywheels onto motors. No heat, no forcing, and no fuss.
Never a problem.
I guess I could get out the good old 4 ton porta-power if I had a problem, but that would just cause more problems.
Ask NWSL and some of the other posters who have had to fight unbalanced flywheels, not me. I don’t have issues with concentricity or balance, and I know how to avoid bending shafts (or damaging armatures, etc. – that is, most of the time. The fun is that even a very slight bend usually would show up as imbalance, and I’m not sure that many of these imported motors use proper steel in the shafts.
Balancing them after installation is not that much of a job, either, although you have to jig the motor a bit carefully to figure out the points to reduce. Checking them for static balance before installation is imho trivial; enough so that I don’t ASSume the things are perfectly concentric or balanced as provided.
Certainly using C clamps (with a ball pivot on the screw jaw) would get the job done nicely, although if it had an Acme or equivalent screw I’d want to grease it.The one advantage of using a vise is that you don’t have to hold the clamp, the flywheel, perhaps the mandrels, and the motor in careful alignment while turning the screw in.
I do have concerns that some modelers might use the considerable force or ignore something wrong when doing this sort of operation – NWSL would not put all those caveats in its instructions for no tangible reason. This in particular when removing flywheels that are particularly recalcitrant for some reason, or if a replacement motor has a slightly different shaft diameter that goes unrecognized. I was trained not to leave a drilled hole unreamed if it were to be given an interference shaft fit, but that appears to be precisely what NWSL recommends if the fit appears ‘too tight’ when engaged. In this context that is probably dixie quality for dime problem again.
In fact I’ve taken to using modified adjustable bar clamps to reduce the amount of ‘turning’ involved with very long fine-thread clamp screws. I note that some of these clamps are made with a hex that will fit a nutdriver to semi-automate some of that… if you stay out of the way of the whipping handle!
Thanks everyone for the info! I have been able to place 3 non-conductive washers in front of the rear flywheel totaling .045" and .015" behind the front flywheel by splitting washers and putting them over the shaft! It seem to work for now but if it looses a washer or wears one out I will then try the flywheel removal process… and I will have to be prepared to replace the motor should something go wrong during the flywheel removal!
That is something I didn’t see coming! And no real reason why it shouldn’t work a reasonably long time, especially if a couple of the washers are reasonably slippery like nylon. Pity the self-lubricating ones I know of (e.g. acetal/Delrin) are too brittle for this method… does anyone have recommendations for this?