Harvard/Stickney Jr Model

[Stefan-K]

The plans call for two 10-32 set screws in the flywheel hub.

Edit: The flywheel is keyed to the shaft, so the set screws are there just to retain the flywheel's axial position.

Any & all help and advice is appreciated.
John

Hey Jon
Just a hint. Set srews a not a good idea.
Please keep in mind, that when you use the setscrews as the plan calls for, they will press a mark in your crankshaft when you fasten them that makes it almost impossible to remove the flywheel from the crankshaft. This is my own personal experience.
BTW Nice build!

 

[JPar]

Hey Jon
Just a hint. Set srews a not a good idea.
Please keep in mind, that when you use the setscrews as the plan calls for, they will press a mark in your crankshaft when you fasten them that makes it almost impossible to remove the flywheel from the crankshaft. This is my own personal experience.
BTW Nice build!

Thanks for the response. I decided to position the set screws so they bear on the key, which I'm hoping will avoid that problem.
Now that spring is here, I've been busy with other things and progress on the Stickney has been slow. I did lap the valves as mentioned in an earlier post. I put the cylinder, piston, and head together to check the compression. The rings are a little stiff, but the compression seems pretty good. I think it will be good enough to run.
Now I have to figure out how to broach a keyway in the timing gear. The shaft is only 5/16" diameter and I don't have a collar that small.
John

 

[awake]

John, you've definitely made the right choice in putting the set screws over the key rather than over the shaft.

That said, my own limited (one model) experience has been that this approach has an aggravating tendency to loosen, especially on the flywheel. I also had a problem with the ignition cam coming loose; it too is also secured with key + set screw. I put blue thread locker on the set screws, and that seems to have fixed the ignition cam, and definitely improved the situation for the flywheel ... but still the flywheel set screws loosen over time. Interestingly, the gear on the crank shaft, also secured with key + set screw, has never given a bit of trouble.

I have wondered if part of the problem might be that I wound up with the fit on the key in the flywheel just a little loose - it is perfect on the shaft, but just a bit big in the flywheel. Particularly with the mass of the flywheel, this allows it to "wiggle" a bit under the uneven forces at work on it, which in turn works the screws loose ... again, this is just a theory at this point. Hopefully, YMMV!

On edit - I was looking back through the thread, and realized that I had already posted most of what is above. I apologize for the repetition. I am sure it is not age at work. I am sure it is not age at work. I am sure it is not age at ... wait, did I already say that??

 

[almega]

I don't know how deep the threaded hole is for the set screw, but if deep enough you could put a short set screw in and tighten to the key and then add a second set screw on top of the first and it should stay in place. You could also see if you can find a nylock set screw which would not be as likely to loosen. I know they are available in 10-32 from Fastenal.

 

[Stefan-K]

My solution for this is, I´m milling a small flat spot on the crankshaft where the set screw left its mark. The screw can sit really thight on this flat and you will have no problem to remove the flywheel if necessary.

 

[awake]

My solution for this is, I´m milling a small flat spot on the crankshaft where the set screw left its mark. The screw can sit really thight on this flat and you will have no problem to remove the flywheel if necessary.

Interesting - I've not tried this with an engine, but in various shop tools, this approach has seemed to be more susceptible to having the screw loosen. Of course, that may just mean that I am using inferior shop tools ...

 

[Cogsy]

Interesting - I've not tried this with an engine, but in various shop tools, this approach has seemed to be more susceptible to having the screw loosen. Of course, that may just mean that I am using inferior shop tools ...

I think, but don't know for sure, that if you machine a flat for the set screw then you have to get the screw exactly perpendicular to the flat when you tighten it. If it's on even a slight angle, the shaft can rotate a touch and this releases the tension on the screw and it invariably comes loose.

 

[awake]

Oh, yes, that is definitely true. But I've had a couple of tools that, even with every effort to get it "just right," sooner or later come loose. Maybe the flats aren't cut right, or more likely, the screws are a bit off-center. On one of the problem tools I finally re-machined the shaft and pulley to take a key ... need to do that with the other one.

 

[JPar]

I don't know how deep the threaded hole is for the set screw, but if deep enough you could put a short set screw in and tighten to the key and then add a second set screw on top of the first and it should stay in place. You could also see if you can find a nylock set screw which would not be as likely to loosen. I know they are available in 10-32 from Fastenal.

I like the idea of a second screw, but unfortunately the hole is not deep enough. When I eventually get the engine running, I plan to keep an eye on things and if the screws have a tendency to loosen I'll try Locktite or the nylock screw you mentioned.
John

 

[almega]

How shallow is the setscrew hole? Nylock setscrews in 10-32 are available as short as 1/8" long, so two of those would only require a hole 1/4" deep. Your idea of Locktite would work as well if you use the right kind.

 

[Chiptosser]

Gentlemen!
Is there a reason, why you can not make a tapered key for the flywheel?

 

[Brian Rupnow]

Industry standard is to have one set screw over the keyway and one at 90 degrees to it. Experience has shown me to use a large enough diameter hub that the set screw has a minimum of 3/16" of material to pass thru, and to never use a set screw smaller than #8.

 

[awake]

Gentlemen!
Is there a reason, why you can not make a tapered key for the flywheel?

In my case, I haven't yet figured out how to machine the tapered key slot with my shaper.

 

[ALEX1952]

Tapered shafts and bores commonly have wood-ruff keys and are generally retained by a nut, a tapered key would serve no usefull purpose as one end would be very deep in the shaft depending on taper, a parallel key does the same job, again you have to find a way of keeping the assembly together as they will try to part.

 

[JPar]

Tapered shafts and bores commonly have wood-ruff keys and are generally retained by a nut, a tapered key would serve no usefull purpose as one end would be very deep in the shaft depending on taper, a parallel key does the same job, again you have to find a way of keeping the assembly together as they will try to part.

The flywheel bore & crankshaft on the Harvard/Stickney Jr. model are straight.
John

 

[ALEX1952]

Sorry this was in respnse to the chiptosser question which on second reading I think I got the wrong end of the stick, he is meaning to taper the key and drive it home, which I have never been a big fan of as they can fret and become loose then they get a whack with a any blunt instrument till its eventually kn*****ed won't tighten any more and the keyway is probably damaged.

 

[Chiptosser]

This the the method use for over a hundred years an flywheels and pulleys on shafts.
If the taper is not right, there can be problems with loosening or cracking.
That is why there is taper per-inch information, to properly size the key.
Woodruff wasn't that common or easy to do way back. Time and labor was cheap compared to tooling.

 

[JPar]

For the past few months, work on the little Stickney has taken a backset to other projects. I'm trying to get back to it now, before I forget how it all goes together .

The plans call for a key as well as a set screw in the cam shaft gear. The builder drilled and tapped the gear for a set screw, but did not broach the keyway. I've acquired the specified broach (1/8") and collar (5/16") and am ready to do the job. I'm wondering if there are any "tricks" to ensure that the keyway is centered on the set screw hole? Or is it just a case of "line it up by eye the best you can"? (My brother used to say "A good eye is better than a bad measurement!")

Thanks,
John

 

[Cogsy]

Lots of people advocate for 2 set screws, one over the key and one at 90 degrees to the key. So you could call the one you have the 90 degree one and place the other over the keyway once you've broached it.

Otherwise, maybe have the screw in the hole with the wrench on it and indicate the wrench handle? It depends how sloppy a fit the screw is but it should get you close.

 

[Chiptosser]

You have to be careful about putting the setscrew over top of the key.
Make sure that the hub is thick enough, where both the key and setscrew will be. If you fit up a tappered step key, it will be as the original was made.
They didn't use set screws in the old engine flywheels.