8-1 Startomatic flywheel repair

[jimboz]

Hi all,

First off, thanks for providing this forum and the input that makes it such an informative site.

I'm rebuilding a 8-1 startomatic and would like your opinions on my planned flywheel repair.  The drive side shaft and bore are a mess and I'm planning to repair by cutting the shaft down to 1-15/16 and boring the hub to accommodate the locking assy below. 

Thanks.

[Thob]

Is there going to be enough hub left after boring it to 3.15 inches? (Dimension "D" in the drawing).  The hub is going to have quite a bit of force on it with the expanding locking assembly.  You don't want it to crack...

[DirtbikePilot]

I'd make a 1/16" sleeve and machine the flywheel and crank to make that sleeve fit. Then drive the key back in and it should be good to go. This would minimize how much strength you loose in the assembly.

[jimboz]

The hub is approx 4" so it leaves me about 1/2" each side, plus the startomatic flywheels are virtually solid to the rim so i think i'm ok there.

I thought about the spacer but the keyways are so bunged up i don't think I could reuse them as well as it seems to me the locking collars are a overall superior design.

[M61hops]

Hi Jimboz, that looks like a good way to go to me  !

[jimboz]

The only potential issue I'm seeing is the fact that they're keyless, so i'll have to be careful about alignment to get the balance right.   My hope is that since there's no balance drillings in the flywheels a few degrees of misalignment will be alright.

[Thob]

If you can bore it to a taper, I'd use one of the SK size QD bushings instead.  It would be a lot less material to bore out, plus you get to keep the keyway.  You would also need to drill and tap the holes for the cap screws that install the bushing.

I don't have any trouble boring a taper, especially if what I want is a straight hole.  Boring a exact taper isn't something I know how to do, at least not yet.  I'm guessing you could put the flywheel on a rotary table and use an end mill to bore the hole.  You could either tilt the mill head or tilt the rotary table to get the proper taper.  Don't forget to tilt it 1/2 as much as the total included angle.  I'd try it on a piece of scrap first and see how well the bushing fits before I tried it on a flywheel. 

[jimboz]

I started looking at the taper locks but I couldn't find one with the length I need without the large end of the taper getting too big.  Seems like the best I could find was ID=1-15/16", Length=3.0" and large end of taper 5".  Do you know of of a mfg with less taper?

[38ac]

Hi,
Lots of CS flywheels  have been bored to accept a "QD" type bushing. This is what a lot of people call a taper lock but that is in error. Link to chart is attached I think you would be looking at either an SD or SK type. The machine work shouldn't challenge a decent machine shop just be surethey understand the importance of the key location. Reliance (Dodge) offers all types of stepped keys to get you from the bushing key to the shaft keyway or ask the shop if they can recut the bushing to same as crankshaft. Last one I had in the shop with QD bushed flywheels had the bushing keyways cut so as to use the tapered gibb keys. Some pretty fancy machine work involved there.

Butch
Link to PDF file  http://www.baldor.com/products/PowerTransmission/catalog/Bushings%20&%20Hubs/QD%20Bushings.pdf

[Thob]

The QD bushings (in SD or SK size) are only going to go into the flywheel about 1 1/4 inches.  I think the "normal" way is for the rest of the bore to remain straight and rest on the shaft.  In your case, where you need to clean up both the shaft and the bore, I'm not sure what the best approach is.  Is it possible to use two of the bushings, one on each side of the flywheel?  You'd clearance behind the flywheel to wrench on the bolts.

I think the key on the QD bushings only needs to go between the shaft and the bushing, since the bushing will be indexed to the flywheel by the cap screws (assuming it's put on correctly to start with).

Does your 8/1 have internal counterweights on the crank?  If it doesn't, then the counterweights are part of the flywheel and getting the keyway aligned is important for balancing.

[jimboz]

Really appreciate having knowledgeable folks to bounce these ideas off of... thanks gents.

I thought about using two locks too, but it seems to me that would set up some tension in the hub as I think the wheel is supposed to move up the taper upon tightening.

My flywheels have three holes (two opposed big ones and a unapposed smaller one) so i suspect the balancing is done with the flywheels.

I'm still leaning towards my original selection because the straight bore is so much easier (cheaper, although lock assy is more expensive), primarily though, because I can center the wheel on the locking assy so there's no moment on the wheel.

[38ac]

That style lock, I call them European taper locks, LOL, will definitely hold the wheels they are very strong. We have them on some equipment at my work. Two things, A set of instructions comes with those locks as to how to tighten them, follow it to the letter! Also be certain you devise a means locate the flywheels before you machine away the key way. The weights dont have to be very far out of phase with the  crank throw  to turn your smooth running engine into a walker.

 Next time I have some converted flywheels in the shop I will take some pictures, sorry.
 

[BruceM]

Hi 38AC.  How do you think these CS flywheels and shafts get buggered up?  Keys walking out while running?

 

[38ac]

They have been run with the gibb keys loose, plain and simple. To work as intended the fit of flywheel to shaft must be good and the keys must be tight, lose either one and things go south in a hurry. Guessing that 1 out of 5 engines I have laid eyes on has had some type of repair to one or both the flywheels.  I see lots of QD bushings, a few bushed flywheels and a few ringed  flywheel hubs.  When the keys get loose the hub often there will be cracks starting at the corner of the keyway. If caught soon enough a field fix is to machine the OD of the hub and shrink a steel ring over it. My model TL has been repaired in that manner. Good flywheels are a tough pull, even in the lister land O plenty so I am told.  The repair Jimboz is contemplating is not experimental, its been done many times before.

[Bottleveg]

The other thing that happens is the key comes loose, drops out and the flywheel free wheels. The flywheel is softer than the crank so the centre hole ends up too big and often oval.
It’s something to watch out for if buying second hand flywheels. Worn ones were often ‘put to one side’ years ago and now nobody knows they were scrap.
I think my current 8/1 had a new flywheel fitted as it has no engine number.
  Mark.