Inspiration for new air motor

[Brian Rupnow]

Yah, I never stay bummed for long. Weatherman is calling for mid sixties temperatures by Tuesday. I'm just tired of endless winter.

[NickG]

As it sits, looks like a mechanical puppy.


 

Wow, the resemblance is uncanny but sure it won’t look like one with the flywheels on!


Sent from my iPhone using Tapatalk

[Craig DeShong]

Brian
I’ve machined buckets of railroad wheels and a few flywheels so I have a bit of expertise.  The best advice I can give you is when you center the flywheel on the lathe do not focus on the center hub but rather on the inside of the outer rim (see (photo).  You will be machining the outside of the flywheel “true”, so if it is out of round, your machining will fix that.  If the hub is a little off center, no one will notice’ but if the inside of the rim doesn’t run “true” it’s very noticeable. Does this make sense?

[Brian Rupnow]

I have to make a new angle for my dangle!! The straight pivot bar that rocks back and forth as the engine runs is just too close to the cast cylinder when the piston is at top dead center. It won't let the crankshaft make a full revolution. I have milled, filed, and sanded away the end of it until I finally decided "This ain't going to fly". I have a new one designed that still keeps all of the important pivot points in the same plane, but the bar has a curve added to the bottom so it will clear the pivot bracket and the end of the cylinder.

[Brian Rupnow]

Yes Craig, it does make a lot of sense. CWelkie has posted the method he used in post #95 of this thread., where he make a "fixture" from wood that was a "precision fit" into the inside of the outer rim and about 2 or 3" thick. The fixture was mounted in a large chuck and the cast flywheel was held in place by "capture plates" across the spokes. This allowed them to machine the outer diameter of the flywheel to be concentric with the inner diameter, face both sides of the rim, and machine the centerhole and one side of the hub all in one set-up.---Brian

[NickG]

Couldn’t you just put it in the 4jaw and clock that rim turn the bits you need to then put on an arbor and turn the rest?


Sent from my iPhone using Tapatalk

[Brian Rupnow]

Couldn’t you just put it in the 4jaw and clock that rim turn the bits you need to then put on an arbor and turn the rest?


Sent from my iPhone using Tapatalk

Probably--i haven't got the parts yet, so I will have a clearer idea of how to go about it when I have the parts in my hand.---Brian

[Brian Rupnow]

I got off early this afternoon from my "real" job, so I came right home and built a new pivot bar for the engine I am working on. Now, although everything is very "stiff" I do have it so that the crankshaft can rotate thru a full 360 degrees. There is still a fair bit to be done on this engine, but I always think it's a milestone when I get all the big pieces together and can go thru a full rotation of the crankshaft without something going "clunk".-----And I have no idea why Mr. Hand is in the preview!!!
<a href="https://www.youtube.com/watch?v=q0mZefCfBoE" target="_blank">http://www.youtube.com/watch?v=q0mZefCfBoE</a>

[Brian Rupnow]

These guys just showed up in the mail. They measure about 5.1" o.d. with a 0.520" wide face. I was expecting them to be a little heavier, but since I never bought flywheels before, I wasn't sure what to expect. Hopefully, they will serve the purpose. I guess I'll find out as I go along. I have paid over $100 Canadian funds for these, including the shipping by mail. I have to wait and see my bank statement before I'll know how much more than $100 they cost.

[NickG]

Were you expecting aluminium castings Brian? I thought they would be iron, I see why you are using two now.


Sent from my iPhone using Tapatalk

[MJM460]

Hi Brian,

In a flywheel, you are not looking for mass, but moment of inertia.  Mass is only a small part of the equation for moment of inertia. 

Each little bit of mass has to be multiplied by its distance from the axis of rotation squared.  So if you place the rim twice as far from the axis, it contributes four times as much to the moment of inertia, even when you thin down the dimensions so the larger diameter rim is the same mass.  The units of moment of inertia are kg.m2.

It is quite possible to make a larger diameter flywheel from aluminium with less mass than a smaller steel one, but similar or larger moment of inertia, so just as effective for your engine flywheel.

I don't want to hijack your thread, which I never miss reading, so I will add a little on how to do the calculations in my thermodynamics thread.  I often stray into other theoretical areas on that one.  Please let me know if you would rather I took an alternative approach.

MJM460

[Brian Rupnow]

Those flywheels are cast iron. Brand new cast iron with no rust. They pass the magnet test. I never thought about aluminum flywheels.

[NickG]

Brian that’s good, they look like alu on the pic! Surely mass is the biggest pay of the equation as that’s is the multiplier I.e a lead flywheel of the same proportions will have a greater moment of inertia than an aluminium flywheel due to the mass x


Sent from my iPhone using Tapatalk

[Brian Rupnow]

The cylinder head and the valve body are finished and assembled. I spent a couple of hours chasing down "tight spots" in the assembly, and now I have it so it will turn over very easily. I'm going to take the rest of today off and read a book!!

[Brian Rupnow]

Who can tell me where I can get outside circlips  that fit into a groove cut into a 1/8", 3/16" or 1/4" shaft, and the tool that you use to insert them? I always have a bunch of 1/8" pivot pins on the stuff I build, and never have a good way to keep them in place. I know there is an insertion tool for metric circlips, but I have never seen one for inch size circlips. Circlips are also known as external snap rings. I have a terrible time trying to put them on with pliers. Before I can get one in place, I have lost five others zooming across my room and disappearing forever.--Whoops---I may have answered my own question.--I checked out the Spae Naur catalogue looking for alternative names for these things, and I see that they sell the tool.-Brian