Flywheel wobble ?

[lowspeedlife]

I would like to make this modification to my wheels. I truely hate gib keys.  From my measurements the whole hub area would need to be reduced, as there is not enough of the hub to recess the bushing into it. To make the modifications it would likely take a vertical table lathe, I have an old friend in Burkitsville, Md with one of these in PA. The lathe is so big the building was built around it. I need to see if i can find my old friend.

Scott R.

[Ronmar]

You say the pen contacted the side of the flywheel directly opposite the keyway?  That sounds to me like the taper of the key dosn't match the taper of the notch broached in the flywheel.  The upper face of the key should make contact with the roof of the flywheel notch along it's whole length.  It sounds as if your key is only making contact on the outer half(toward the head end of the key), causing the wheel to be held in place at an angle.  

Withdraw the key and use a lit candle to blacken the upper face of the key with carbon.  Drive the key back in and then remove it again and see if there are witness marks along it's whole length.  If the marks are not along it's whole length, then the key is not fit properly.

If the key is fit properly, it should slide all the way in before it contacts, then it engages the roof along the entire length.  A little bit of driving the key takes up the slack between bore and shaft, and the bore opposite the keyway gets drawn up evenly against the shaft directly opposite teh keyway.    

[veggie]

I will pursue the key fit first. Then I will investigate the taper lock system / new flywheel.

Where can I get a few new gib keys?
The ones I bought have a nice finish, but they slide all the way in and don't interfere until the key head hits the hub (hence my use of a shim).

I need something that has lots of interference, then I can shave it to the perfect fit.

veggie

[Ronmar]

I don't think there is enough meat in the hub to allow a proper taperlock retrofit, especially considering the possibility of voids in the hub casting.  

Here is a drawing that illustrates what I was saying about the gib key fit.  The one on the left is a properly tapered key.  The one in the middle is a key with too steep a taper, and the one on the right is a key with too shallow a taper...  With a properly fit key, the bore opposite the keyway should be in contact with the shaft surface for the entire width of the hub.



I don't know who has keys, but you could always make your own from plate thick enough to fill the keyway.  One way to get a good gauge of the keyway shape/taper is with a piece of soft wood cut to the rough shape of the desired key.  Roll the shaft so the keyway is pointing down.  This will allow the opposite side of the bore to rest on the shaft along the entire width of the hub.  This should place the flywheel perpendicular to the shaft and make the keyway opening the tallest it will ever be(where it would be with a fully seated, properly installed key).  Then lightly push/tap in your wood key and see where the wood makes contact with the flywheel keyway.  You can then remove wood at the contact points till the wood key goes all the way in and makes full contact along it's entire length.  Candle soot also works well for the final fitting.  Once you get the wood key to fit, cut a steel key to match it and repeat the process  on the steel key with candle soot for final fit.  

Before you start this process I would reccomend that you make sure the roof/bottom of the tapered keyway in the hub is flat, and has no bumps or dips in it.  You can eyeball along it's length with a straight edge and bright light to confirm it's true along it's entire length.  If it is not smooth, small imperfections can easilly be trued up with the edge of a large straight edged file

[veggie]

Ronmar,

Thanks for the well explained procedure on fitting a key.
Your sketch (very good I might add) illustrated the same theory as I was trying to show in my earlier picture.
As nicely finished and tapered as my replacement gib key was, I think the taper did not properly match the bore's keyway.

It's a real pain for me to remove this flywheel, I have to relocate the rig, remove the exhaust system, and then assemble my engine hoist to lift it off         (can you hear the violins playing   )

Thanks again for you directions,
veggie

[Ronmar]

It's a real pain for me to remove this flywheel, I have to relocate the rig, remove the exhaust system, and then assemble my engine hoist to lift it off         (can you hear the violins playing   )

Ahh the joys of working with big iron...

[Crofter]

I used the description "taper lock" as a catch all term though it is a brand name of only one style. I believe the QD style of tapered bushing requires much less material to be removed from the hub bore. The weakest link in the existing hub locking design is the huge gash for the gib key which exerts concentrated force on one spot. The evenly directed force of the taper bushing in SK size may not be more of a hazard to the hub splitting.

A 1/8 wobble is a lot of force trying to right itself into the plane of rotation: nearly 5 lbs several inches off center line. I would worry about that and want to know why.

[veggie]

Crofter,
Depending on the bushing, (QD, SH, P1, etc...) very little meat may need to be removed.
I have a QD 2" bushing from the sheave that I had installed on the Lister shaft at one time.
At first glance, it does not look like much material would have to be removed from the bore to create the necessary taper.
This is an option I plan to explore so I will report back after doing some measurements.

Part of the decision process will be the price. The cost of machining and truing could be prohibitive.

veggie

[Crofter]

Crofter,
Depending on the bushing, (QD, SH, P1, etc...) very little meat may need to be removed.
I have a QD 2" bushing from the sheave that I had installed on the Lister shaft at one time.
At first glance, it does not look like much material would have to be removed from the bore to create the necessary taper.
This is an option I plan to explore so I will report back after doing some measurements.

Part of the decision process will be the price. The cost of machining and truing could be prohibitive.

veggie

I have not had the SK bushing in my hand and cannot at the moment find the specs on it other than its max shaft size of 2.125 so it is not huge. The smaller bushing for the 38mm gen pulleys take out only a bit more than 1/4 inch tapering to almost nothing.

I can swing 22" in the gap of my lathe but have done larger things like tractor wheel to truck wheel conversions using my tractor rear axle as the lathe head and the cutting torch and hand grinder from a pedestal. Completely redneck, not pretty, not safe and not accurate enough to do precise tapers, but where there is a will there is a way! Any decent sized machine shop could handle it easily but the setup time, plus drilling and tapping the holes would make it at the very least a $200.00 job at a shop I am familiar with. The bolt holes take more time than boring for the bushing

I hope that it is gib key issues but it would not surprise me to find a bore that is totally out of whack with the rim. I saw a bronze timing idler gear that had an off center, crooked, plus out of round bore; it appeared to have a hole that was broached rather than turned.

[Rom]

I had a VA drive flywheel done out here. Got charged 180 for the taper lock, and 2100 for the machining. The fella smoothed out the hub face (same face as flywheel face we run the belts around) Machined a ring that fit that so there was a surface to thread the taperlock bolts into. He machined down the bush to a thinner size so he wouldnt take out too much of the orginal bore of the flywheel, and made a step key to mate the taper lock keyway to the lister crank.

Loads of fun and cash, but shall never fall off.

Doubt I would ever bother to do it to a listeroid. One of the fellas out here that used to be the goto guy for RA Lister used to drill 2-3 holes through the hub, and put square headed set screws in. Was a standard practice by him from what I understand, and flywheels didnt come off after such a procedure. Looks ugly and dangerous if something caught it tho.

Rom

[veggie]

Rom,

That's a very interesting (and simple) fix.
I don't like gib keys, so....if I understand you correctly he did something like the picture below ?
This would be much less expensive that boring for bushings.
As I see it, the two set bolts would evenly locate the flywheel in just the same way as a tapered gib key.

Anyone see a problem with this ? The placement of the bolt is up for discussion also !

veggie

[veggie]

It might be a good excuse to just make a new flywheel out of plate steel (and heavier).

Jens,
I thought about making a new flywheel, but then I would have to make two or it would look funny.
I am limited to what I can spin in the lathe I have access to, which is 16" diameter.
Fortunately, my engine has the counterbalanced crank, so the flywheels could be solid and without offset weights.
I am still assessing how much heavier I would have to make a 16" flywheel to get the same inertia effect as the current 23" flywheels. The idea is still alive but requires a bit more evaluation.
The proper way is to get the majority of  the weight on the outer section of the flywheel for maximum momentum. Also a center hub is needed with a keyway and probably a tapered bore for a bushing.
A lot of work for a machinist. Especially if two are needed.

veggie

[Ronmar]

I think locking colars are a way better method of maintaining the gib key to hub relationship.  One collar on the inside to hold the hub, and one on the outside to hold the key in place in the keyway...  I am talking about the two piece collars.  On the inside, this has the advantage of being easilly removed to free up 3/4" of space behind the flywheel when it comes time to remove the gib key.  It would also be a fairly simple matter to incorporate a key puller into the outer collar by drilling and tapping the collar horizontally, and having the collar set over the key head and the key head welded to the collar.  A 2" ID washer on the Inside of the collar would be a plate for the puller to come up against instead of digging into the flywheel when pulling the key/collar.  

[veggie]

Anyone see a problem with this ? The placement of the bolt is up for discussion also !

Oh yes .... !!!
First, we are talking two or three set screws and not just one.
Second, can you imagine the forces on those three set screws, the hub and the shaft ?
Now maybe I don't understand things right and the three set screws are only there to secure the flywheel to not fall off. I could see that .... but the way I read it is that he attaches the flywheel with two or three set screws period  (no fitted gib key) and that IMHO is very stupid.

I thought there were no stupid questions, just people too stupid to ask questions?

The sketch shows a key fitted (yellow) which is installed.
The sketch also states TWO set screws, one on the opposite side of the flywheel and therefore not visible.
Two set screws sized appropriately may be able to exert a radial force on the hub which could exceed that of a gib key and provide considerable locating force.
If a set screw were acting directly onto the key, there may also be some benefit.


veggie

[veggie]

Ronmar,

Sorry, but I'm having trouble following your description.
What "two piece collars" are you referring to?
Does you solution involve a gib key or a standard straight key a shown in my sketch?
Are there any set screws in your scenario?

thanks,
veggie