The Steamboating Forum

Sorry, I didn't take a picture.

Nyitra has it's propellor shaft below deck under what I call the propellor strut.

On the propellor shaft with the new drive #2 it's a cast steel martin sprocket bushing and a stainless HTD 30mm pulley.

I tried to drill and tap a set screw into the bushing , but it's a cast steel and it was too thin for the screw 1/4"-20 I chose and it cracked.

I noticed that the crack of flange of the bushing had degraded - but given time and space constraints I couldn't get it off. At a friendly marina where I was allowed to use their tools I got it in a big vice and we tried using a 3 jaw wheel puller and could not get the stainless pulley off. When using the puller off it was just bending the pulley shoulders.

Probing with some punches, prying and banging with a forked-prybar and hammer acheived nothing.

I figured if it was on that tight I could not try to set any records and limp to her docks at Chautauqua lake. I kept the speed to 2knots and made it the 2miles.

But now I have to figure out what to do. It's nerve racking to know your pulley could potentially fall to the bottom of the lake anytime.

Main Options:
1) Forgo removal and figure a way to permanently attach the pulley and bushing to the shaft. I don't know if welding cast steel to stainless steel is possible. Can a bit of stainless be welded from the ss pulley to the ss shaft?? I have oxy-acetyl and don't really do any electric welding.
2) Figure out how to remove it. (Haven't tried heat)
3) Replace the whole shaft - I really want to avoid this. It's a true shaft that I paid maching for the taper and the dimpels.

Normally this part has jacking screws that make quick work of separating the bushing and pulley - but due to my ingenuity the flange of that bushing has cracked off.

This cast steel martin sprocket split tapered bushing:
https://www.mcmaster.com/#6086k195/=18aw4cf

is broken inside of
this stainless steel martin sprocket:
https://www.mcmaster.com/#1230n27/=18aw3ri

on a 1.25" 304 SS unkeyed shaft (there is round machined 1/4-20 set screw dimple.

Ideas?

-CB

cyber,
I have used these bushings for years with no problems. I can't tell from your description whether you used the tapped jacking holes in the bushing to remove it. Use the holding screws, just take them out of their threaded holes in the pulley and thread them into the threaded holes in the flange face. Are the threaded holes in the bushing face ok?.I have always had the bushing release with a few turns of the screws. The literature for the taper-loc bushings claims it develops the holding power of a shrink fix, so gear pullers will not help if the bushing will not release.

The torque spec for the bushing is for clean dry threads and the same for the taper as well. Long ago when I was sure I knew more than I know now I assembled the bushing with anti seize. The bushing bottomed against the flange with very little torque on the bolts, I was lucky I did not split the pulley.

Using the jacking screws is the only way I know to get the bushing to let go, I have never found a way to apply a wedge. The screw works so well because the force is contained between the bushing and pulled with no stress on the shaft or hull.

Hope this helps. Happy steaming, best regards, Steamboat Mike

To use someone else's phrase Mr B., "Houston, we have a problem". Most types of stainless sieze together (= micro-weld together) rather well unless you add something to stop them, and I think your shaft/bushing/sprocket combination is now a permanent unit.

Having, for my sins, examined literally hundreds of welds from 304 to 304 in an electron microscope, I'm afraid it is rather prone to impurity migration while welding, and then brittle fracture into cracks at the weld surface, which are too small to see immediately, but grow and cause failure later. 304L is a lot better, but it's too late saying that to you. My advice then is not to weld.

If there is enough free shaft beyond the sleeve flange, I'd be inclined to make up a new floating flange, a loose fit on the shaft, and use the original tapped clamp screw holes (if the screws will come out), and just tighten the new flange to the sprocket sandwiching the broken one. There should be no need to make it particularly tight, but it should ensure nothing comes adrift.

An alternative would be to solvent clean everything, warm it up to 60C or so in an oven, & then run a good grade of epoxy into the cracks and joints. It's amazing how far epoxy will creep into cracks when uncured and warm.

cyberbadger,

My bad. I did not notice the part about the broken flange. Not sure if heat will work since the bushing is split and may not open when heated. With everything at ambient temperature try to heat the stainless sprocket as quickly as possible with oxygen-acetylene and rap the sprocket with an appropriate size piece of wood.

You may need to consider cutting the sprocket carefully with an abrasive cutoff wheel. You will sacrifice the sprocket to save the shaft. If you cut a slot in the sprocket that just goes just into the bushing you should be able to do it without damage to the shaft. It is my belief that the bushing is not cast steel but rather is ductile or cast grey iron.

Best regards, Mike

Steamboat Mike wrote: It is my belief that the bushing is not cast steel but rather is ductile or cast grey iron.

It's strong but brittle/granular. Martin Sprocket and Mcmaster carr just say "Steel".

RGSP wrote:To use someone else's phrase Mr B., "Houston, we have a problem". Most types of stainless sieze together (= micro-weld together) rather well unless you add something to stop them, and I think your shaft/bushing/sprocket combination is now a permanent unit..

If this is truly the case this is "desirable". As long is it stays put and doesn't slip thats fine. It's been underwater since Wed. When I get back to Chautauqua tomorrow - probably on Monday I'm going to steam up and secure her tightly to the dock and test her at full throttle. If it doesn't fall of or slip then that would be acceptable for the season.

A related mater - I also now have a spare belt on board, should the newer strong Gates PowerGrip 3 30mm belt break(which I doubt) I can replace it in the water - just takes about 1/2hr of disassembly/assembly shannagins on the deck.

-CB

So it survived all summer.



So it's really stainless pulley, cast steel bushing, stainless shaft.

Hope I don't have to saw that pulley in half.

-CB

These bushings are of course split, and rely on being trapped between the bore and the shaft. If you decide to remove the pulley, chilling the shaft w/ ice and heating the pulley hub should give you enough clearance to drive the pulley in the loose direction on the taper.

- Bart