A brief update, first, on the December cover story, about the BD Tillinghast half-breed. She has finally made her journey across the pond, arriving safely here at the beginning of December. She was lucky to be safe, as at some point, the crate had suffered a close encounter with a fork lift, which had punched two neat holes through the end wall of the crate just going either side of the head of the engine and not causing any damage. Dismantling the crate was cold, but fun, and by the end of the day Tillie was sitting on our trailer. However, getting the trailer into our garden via a narrow, steep driveway which goes off an equally narrow lane at a 90 º angle is not proving to be so easy. Determination is in plentiful supply and she will get in!!!

And now, to business. Some time back, I did an article about running an engine with a flywheel which had a cracked spoke. Much of the discussion then was about the safety issues involved, but this time it was a different sort of crack, on the hub, and the solutions presented were interesting.

* I just got the flywheels from my 2¼ HP Early Style Galloway back from a welder with 20 years experience. I made sure the flywheels went on easy, inserted the key, and as soon as I started tapping it in, it cracked in both places again. The other wheel seems to be okay, for now. Anyway, I will go with this for now, and look into new cast flywheels when I win the lotto.
Rest assured gang, THIS WILL NOT RUN IN SHOWS OR PARADES. But in my shop...well that's another story! I'd be probably digging my own grave if I ever sell it, but then again I don't plan on selling. It was my first!! and safety is definitely #1.
The hubs were both on the inboard side and possibly this happened because the lifting chain was put through both flywheels or possibly because it is not "keyed" right.

* That wheel can be welded but it will need to be in a hot bed to stress relive it till cold, and it should have a lot of peening while cooling, but as said DON'T run it cracked

* I have seen a flywheel come off a crankshaft at a show which had a cracked hub, which I gather is the problem by the description of the fitting and subsequent cracking as the key was inserted. Shrink a ring on it and be done with it!

The idea of using a "sweat ring" brought out a lot more questions and answers, starting with exactly what it is, before progressing to how to fit one and the best material to use.

* A sweat ring is a piece of round metal, which is heated to a high temperature and placed onto the outside of a round metal object which is usually cooled before applying the ring. The ring itself should be 5 to 10 thousandths smaller ID then the OD of the object being repaired. A good practice is to turn the object, in this case a flywheel hub from a Galloway flywheel so that you get a good surface. After placing the ring onto the object, let them cool down naturally. Meaning just leave it till it is cool. This same principal can be applied to a sleeve, but the OD of the sleeve would be 5 to 10 thousandths larger.

* If one were to fabricate a "sweat ring," what kind of steel should be used? I was thinking about using seamless pipe, but don't know it's characteristics.
I need to do a little more research on the cause of the cracks.

* Plain old "garden variety" hot rolled steel works well. Pipe, whether it has a welded seam or is seamless will work, if it can be found in the right size. If you are thinking of repairing a cracked flywheel hub, the ring should be about .005 to .010 smaller that the OD of the area it will be set on, about a quarter inch thick and as wide as conveniently possible. Put the flywheel in the old girl's deep freeze and warm the ring up to a black red. Drop it on, making sure it is the right place and let it all cool/warm up to ambient.
A ring shrunk on the hub is a good repair. The centrifugal forces placed on that hub are minor compared to those placed on the rim. Contrary to what some may think, the chances of those flywheels, with a good repair, exploding are about the same as getting hit by a U-Boat in Downtown Pittsburgh. Chances that using those flywheels will destroy life on earth as we know it are pretty slim.

* While I don't feel this flywheel would ever explode, I don't think it will stay in place on the crankshaft. Since it is a Galloway flywheel it is worth repairing (ie rare). That said it is worth repairing correctly.
Believe it was suggested that CRS was a suitable ring material. I would recommend you use a good, readily available alloy with good heat treating characteristics, such as 4140. I also recommend using at least pre hardened 4140 or even better heat treat it to Rc 40/45.
Realistically you can make this ring .002 to .010 interference fit. If you use dead soft CRS, the higher interference fit is a mute point, because as the ring cools the hoop stress will exceed the yield strength of the CRS and the ring will stretch, thus limiting the amount of available compression you can put on the hub. However, if you use a heat treated alloy, that ring will tolerate a much greater hoop stress before failing/ yielding. What this boils down to is that by using a high strength ring you can make a much smaller ring to do the same job. This will allow the repair to be inconspicuous, and with a little effort the repair could be made to match the original contour of the hub. Equal attention should be given to preparing the hub. The hub should be turned to allow 100% contact to the ring. If not the ID of the flywheel will become egg shaped.

* Prior to installing the sweat ring and in order to true up the hub, couldn't one take a metal hole saw and using a drillpress, slowly lower it down on the horizontal hub? Lots of lube and cooling needed here, right? I would think that alignment regarding the crankshaft hole would not be a factor. Just how hard is this cast??

* I like the idea of press fitting a ring around the hub. I'll stop drill the cracks first. Should I have the cracks brazed first before I install the ring?

I won't paint the hub, but will put some hard film preservative on it, so I can remove it often for inspection. Kinda looks like paint anyway.

* Here is a thought that we came around with. Would a bearing heater get the ring hot enough to get it onto the flywheel? They, if used right, can heat without changing the color. Or has anyone else heated bearings in hot oil? I do this as I like the fact that you have lube in the bearings while you are heating them.
Must work as the bearings, are still in use in the 5020 Deere we rebuilt!
And yes, I am one that is leery of broken hubs on flywheels also. I have seen them, when running, the flywheel comes loose on the crank as it is hard to drive the key in tight. BUT with the sweat ring they should tighten up good. Has no one else ever seen flywheels walk on a crank? Ever wonder why some will do it over and over? Have you looked things over and not see anything wrong? I'm now thinking that they could have small hairline cracks and this could be the reason.

* Another way to shrink your flywheel hub is to shoot a fire extinguisher at it, we have done this at work when need to cool something fast. It's not as good as dry ice, but does work

* Can someone provide some info for the proper interference for a sweat ring? That is, if you turn the hub round and straight how much smaller would the inside bore of the ring be and also how thick? I don't have a cracked hub but it seems like some useful info to store away.

* There is no hard and fast rule here. The greater the interference fit the larger the ring required to support the resulting hoop stress. Here at work I shrink rolling mill sleeves onto shafts with .015 interference! But that hoop stress is supported with a ring of 4340 or H13 alloy steel at a Rc hardness of 43-45. The cross sectional area is 9" sq. The sleeves have an OD of 12", an ID of 8", and are 4 1/2" wide. I'll measure up a hub on a common engine like a 3½ HP Hercules and see what sort of ring dimensions will work well. Betting .002 interference will be just fine.

* Made a few measurements on a 3½ HP Herc last night. The hub is 3 3/8 OD. Max width ring that could be shrunk on is 3/4 wide. If the hub(s) were cut 3/8" deep/side the new hub diameter would be 2 5/8".
Yesterday I speculated on .002 inter fit. I am upping that to .006 after looking at this. Briefly, at .006 inter the pressure between the hub and ring works out to 13544. The resulting stress at the inside of the outer ring is 55ksi. Compressive stress at the OD of the hub is -13544psi.
4140 @ Bhn 302 (Rc32) has yield strength of 95ksi. Therefore pre-hardened 4140 is fine here, with a more that 1 1/2X SF.

* Someone asked about split hubs. If you are lucky enough to only have to ring one side, then shrink the ring on after the flywheel is back on the crankshaft and clamped. If having to do the inside too, I think clamping the flywheel on a piece of TG&P, then turn both sides/hubs. Then unclamp and remove TG&P. Then fabricate a "wedge"(with slide hammer provisions) to support the gap (but not expand it) after you shrink the inside ring on.
Once the flywheel is on the shaft, slide hammer out the support wedge, tighten the clamp bolt, and then shrink the outer ring on.
A little filler and some paint and the hub will look as it did originally.

* I have no experience with this kind of engine flywheels but I have spent many many years repairing all manner of farm equipment with all kinds of cast iron pulleys, sprockets and gears. Many of these run at fairly high RPMs (1500 to 2500). Many times over the years I have had to make repairs with out the best tools or supplies for the job.
I won't present this as "the way", just as how I would likely attack this problem if it were mine on say, a high speed combine pulley, and I wanted to be very sure of it.
First off I would turn the hub with a shoulder for a ring on both sides. Next I would bore the center out well beyond the keyway but leave as much meat as possible. Then I would braze the cracks both inside and out followed by reboring the inner bore. At that point the cracks should be still well brazed but the surface back to clean cast. Next I would turn a loose press fit sleeve for the bore but leave the inside hole undersize. After pressing it in I would braze it in place from both sides. Bore the inside to shaft size and cut a new keyway in the sleeve. The sleeve should be twice as thick as the depth of the keyway. Lastly return the shoulders and shrink on a couple of heavy rings. I might even be tempted to braze those too. If I did I would maybe turn them and the shoulders with a slight taper and press them on tightly. Cool the flywheel and heat the ring well.
Of course I could be wrong but that never stopped me before!

* Has anybody ever considered putting a "tire" on the outside diameter of a flywheel?
Just like anything else, cast iron gets old with use and temperature changes. As things get old, they tend to shrink. It has to compensate for this shrinking by cracking and a cracked flywheel is a dangerous thing to have spinning around.
If one would fabricate a steel "tire" or band such as they did with wooden carriage wheels, I would imagine the flywheel could still be used with less chance of explosion, possibly making it a functional engine?

* I'm not sanctioning what was done, but I know a fellow who shrunk a tire onto a flywheel on a 3 h.p. Fuller & Johnson. In order to make both look the same, he put one on the opposite side, as well. This particular engine appeared to have been rolled down a mountainside. The guy found it all busted up and half buried in the mud alongside a creek. One of the flywheels was in many pieces. He found everything except one spoke.
In as strong a statement I could make and still remain civil, I warned him not to attempt to reassemble the flywheel. He was determined and wouldn't let what anyone said stop him. At that juncture I said that he should at least shrink a tire onto it. He paid attention to that advice, at least.
To replace the missing spoke, he went to the local salvage yard and broke one out of a wheel he found, there. After everything was welded back together and the tire shrunk on, he hooked the engine to an electric motor and tested it by deliberately overspeeding it. He says he will never run it in public. (But, when he passes from the scene, I wonder what the unsuspecting subsequent owners will do?)

* After looking at the pictures of this terribly cracked flywheel hub I personally wouldn't have any problem running the engine with them like that. The crack obviously was caused by someone driving a tapered key in too tight and cracked the hub.
I don't think those cracks are serious enough to loose any sleep over. I wouldn't even bother welding them, put a little JB weld or filler over them so to not scare the people that get worried about exploding flywheels.
I think if you're worried about stuff like that you're probably in the wrong
hobby. None of the stuff we play with is safe or OSHA approved!

* Although I like the steel ring "fix" I also think the flywheel could be used "as is" and if there is a chance of it loosening on the crank, a set screw (or two) could be drilled and tapped for.

The information given here by various contributors to the Stationary Engine Mailing List was interspersed with comments about the safety aspects. However, as these were covered in the previous article about cracked flywheels, I preferred to pass on just the technical information this time. For the owner of the Galloway with cracked hubs, the safety aspect had to take priority.

I, being new to cast, appreciate this more than you can imagine. I love this little Galloway, It did run, prior to restoration. But there are so many people here in Helena, MT, who want to see this baby, I've just got to make it safe. Bottom line - I need new flywheels. I am committed to get safe flywheels.

Happy New Year to all, and thanks to GEM for letting us share some of the discussions we have via the internet with you.

stationary-engine@atis.net

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