Built up fly wheel assembly question

[Metal Butcher]

Plan A: I'm thinking about making a built up all aluminum flywheel and using Loc-tite or JB Weld to assemble it. This is an idea I would like to try.

Plan B: Build a simple and typical disc flywheel with the usual cosmetic Swiss Cheezing. This is a boring option I want to avoid.

All other options and ideas have been exhausted due to a lack of materials.

Will either-or-both assembly options hold the flywheel together, or will this become a fly apart mess during the final machining???

-MB

 

[BMyers]

could you do a shrink fit ?

 

[bearcar1]

Bmyers, I was thinking the same thing. The hub/spokes could be made up and press fit into an inner rim and then a solid outer rim could be 'shrunk' or press fit over that one to cover the ends of the spokes and keep everything in place for final machining.

 

[Metal Butcher]

I can't use a shrink fit since I have one piece to machine the hub and rim from. The shrink fit question gives me another idea that might work. I can slide the spokes in through the outer rim and use JB in the hub holes. Then loctite the spokes at the rim and peen the ends so they expand in the rim. All I need is some luck with the expansion going deep enough so it doesn't disappear when I machine the outer diameter of the hub.

-MB

 

[Brian Rupnow]

Not sure on how you plan on going about this, but I have a great deal of respect for Loctite 638 or 648. As long as the outer diameter of the flywheel is thick enough to give good contact area with the spokes you will probably be okay. I will start a new thread titled "BUILT UP FLYWHEEL" to show you what I am thinking.---Brian

 

[Metal Butcher]

This flywheel would have been so simple using press fits if I had the proper materials.
The spoke rods measure up at .185 and the 3/16 holes are oversize
Compounded since the drilling is purposely off center through both the rim and the hub. This is my first attempt at drilling into material that is not perpendicular to the drill bit and that defiantly causes a problem. I'll give the JB and Loc-tite a go and see what happens, and since its aluminum a failure won't be a great loss.

-MB

 

[Cedge]

Gotta agree with Brian... Loctite is our friend. Here is the first multi-part flywheel i made. Loctite secured the spokes and the outer rim was interference fitted and Loctite applied. Worked like a champ even if I finally considered the engine project less than a full success. Gonna have to revisit that one this spring.

Steve

 

[SBWHART]

Had a go at making a composite fly wheel brass rim ally hub, using the shrink fit route, it worked ok up to a point.

I put the rim in the oven at max 250ºC and the hub in the freezer the bits went together Ok at that temp range the brass hub expands about 2%. My problem was with the hub it was only 3mm thick and made from scrap pistons and I had machined 4mm thick spokes (five off) and the spokes cracked under the load. It would have work ok if the hub was made from thicker material.

But after this experiment I've decided that the loctite route would have been better, I'm going to have another go re-using the brass rim from my first atempt with a new thicker hub but with loctite, in a couple of weeks.

Stew

 

[kvom]

The tractor thread shows a wheel made with spokes screwed into the hub and soldered at the rim. Seems that's an option.

Or mill out the spokes on a rotary table.

 

[cfellows]

This is a method I've used for several flywheels. I used it for a 3" flywheel as pictured in the drawing and have also used it on two different, 6.5" flywheels where the rims were made from 6.5" steel pipe. The spokes are made about .003 - .005" inches too long so the center axle forces them out against the rim.

Chuck

 

[Metal Butcher]

I think I understand. The spokes are pushed into the central tube to clear the outer rim. After the spokes are pushed outward into their final position the solid rod is pressed into the hole in the tube locking ever thing together.

Is this correct?

Wow, this is a very interesting approach that never crossed my mind. I'll have to give it a try someday.

-MB

 

[Jasonb]

If you are worried about the loctite/JB Weld holding why not cross drill and fit say 1/16" CSK alloy rivits or just rod with the ends peined over into CSK holes then give it a skim in the lathe.

Jason

 

[Brian Rupnow]

I think I understand. The spokes are pushed into the central tube to clear the outer rim. After the spokes are pushed outward into their final position the solid rod is pressed into the hole in the tube locking ever thing together.

Is this correct?

Wow, this is a very interesting approach that never crossed my mind. I'll have to give it a try someday.

-MB

Jeez, I'm glad you posted that!! I looked at it for 10 minutes and couldn't see how it would work----and I'm supposed to be an engineer!!!

 

[Metal Butcher]

Brian, that drawing by Chuck had me scratching my head at first.

Then I thought it was Chuck just posting a practical joke.

Then simple common sense lead me to the answer.

Hey Chuck did you really leave out the details by accident? :big:

-MB

 

[fdew]

Very clever idea. I wonder if it could be dressed up a bit by making or buying a reverse ct bore and using it on the inside of the spoke holes. It would give a little cleaner interface.

http://www.browntool.com/Default.aspx?tabid=255&CategoryID=96&List=1&Level=a&ProductID=315

 

[cfellows]

Sorry, all, I thought it would be obvious from the drawings. Of course, my wife is constantly reminding me of important parts that I omitted in describing various things to her! :-[

This design is a little bit tricky to get together. All six spokes are first pushed through the inner ring. Then, the assembly is placed inside the outer rim and one by one, the shouldered part of the spokes are extended out through the smaller hole in the outer rim. Finally, the innermost rod is pressed into the inner ring holding the spokes in place.

Chuck

 

[Metal Butcher]

Thanks guys for all the good suggestions to help me make my fly wheel stay together.
All I really hoped for was some ones first hand experience doing the assembly the way I proposed.
As a precaution I peened the ends of the slightly protruding spokes and the fly wheel stayed together during final machining
I don't feel comfortable with loctite alone holding a fly wheel together for the long term unless its used "in addition to" rather than "instead of" press fits, soldering, brazing, peening, etc.

I'm a bit stubborn at times and its very difficult to get me to try new ideas.

-MB ;D

 

[jpaul]

Some while ago I fell into a post describing a built up flywheel made from salvage yard brass or bronze. A little bit of gold really adds appeal in my opinion so I book marked the page. http://modelengines.info/golden/const/flywheel.html

The process is quite laborious but the techniques used by this builder may be inspiring.

 

[jpaul]

Address correction http://modelengines.info/goldeng/const/flywheel.html