The Steamboating Forum

Hello to all,

As I am waiting for the rest of the materials to continue my engine, I have one mechanical challenge to solve yet. How would you fasten gear wheels onto a crankshaft? The gear wheels will come with a "smooth bore" for the axle, meaning it is just a straight hole without any key channels or fastening screws or anything like that.

Hi Ramon,

i have used locking assemblies BAR and SIG


I have bought them at www.maedler.de.

Best Dietrich

If you want a key-way in the gear, then it's an easy task in a lathe, if you can grind up a simple cutter.

Set the gear in the chuck and ensure it is centred (gear teeth have habit of not falling where you might want), then lock the headstock and set the tool to pass through the bore and slowly move the cutter outwards til you've cut the depth you want. A little slow, but I've done it many times without failure.

The tool can be reversed to cut the shaft if required.

I never heard of locking assemblies, but they seem to work. The size I need would be capable of transmitting multiple times the torque I need them for. I forgot to mention the crankshafts have a tapered segment going from a 10mm/0.4" diameter to 14mm/0.55" and this taper possesses a keyway for a half moon key. So, I'd need to only machine a taper into the gear wheel bore and cut a keyway into it. I think I buy the locking assemblies for the fast solution and the one-cylinder test engine and when the cross slide is upgraded for taper turning (not going to be super soon), I'll do that for the final engine.

TaperLock assemblies are the way to go, you get a matched gear/pulley and hub. Work very well and reasonable price . Here is are examples from Bearing Boys https://www.bearingboys.co.uk/Taperlock ... ets-1121-c. and https://www.bearingboys.co.uk/Taper-Bushes-1134-c

enjoy!

I have used "Po-Boy" keys many times, with great success.

A tap drill is used, drilling parallel to the shaft centerline at the intersection of the shaft outside diameter and the driven component inside diameter. Tap deep enough for two set screws, run the first one down hard, followed by the second one, with some Loctite.

These can be taken apart, and re-assembled, although this can be difficult because precise alignment before replacing the set screws is required, especially if the shaft fits are tight.

The cranlshaft on my walking beam engine is fitted this way, with a maximum running torque of 270 ft-pounds applied to the crank. The picture shows two "Po Boy" keys using 1/4-28NF set screws on a 1-1/4 drill rod shaft. (nearly 6mm x 1 set screws on 32mm shaft)

Thanks for your contribution, too. I remember now seeing this alternative to key-way-cutting and I asked myself if this would really be sufficent to prevent a crankshaft from twisting - or more accurately spoken: from the crank pin to slip on a sub-degree-level, that would already cause a misalignment of both sides of the crankshaft. But it seems to work on your engine. I was always concerned about that with any sort of keyways in general and thought that's the reason they are not used for crank pin-to-web connections.