Author Topic: Fabricating a Flywheel  (Read 9434 times)

Offline tinglett

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Fabricating a Flywheel
« on: November 15, 2016, 01:16:11 AM »
Fabricating a Flywheel

In prep for my next engine build, and because time in 2016 is running short and I'd like to accomplish something, I thought I'd fabricate the flywheel.  I'd like to include things I've never done before:
  • Fabricate spokes, rim, and hub from different parts
  • Cut curved spokes
  • Heat the rim and go for a friction fit with the spokes
And maybe other things will come out of it as well.  I'm hoping a build log of this stuff is ok in this part of the forum.  For background here are a few links and photos from other builds.

Arnold's elmers#5 engine's flywheel caught my attention with friction fitting a plate inside a rim. http://www.modelenginemaker.com/index.php/topic,4087.46.html   Here's a direct link to an image from his build log so you know what I'm talking about.


Don fabricated a flywheel for the Benson Vertical engine here.   http://www.modelenginemaker.com/index.php/topic,3702.255.html  It was made in a few phases including bending the rim from a straight bar of brass if I recall correctly.  Wow.  Here's a link to a finished image, but beware you might need sunglasses for that fantastic shine!


Chris' built-up MEM Corliss build fabricated a flywheel too.  It can be seen starting around here:  http://www.modelenginemaker.com/index.php/topic,5980.270.html

Here's a small image of it

and a big image you should be able to see if you are logged in (otherwise it will appear broken)


Simon's build of the Mancaster's Joys Valve engine also had a nice fabricated flywheel.   The discussion starts here http://www.modelenginemaker.com/index.php/topic,2470.msg75284.html#msg75284

Here's the final flywheel.  Like I said, very nice!  Some silver soldering work there, too.


Jason fabricated a curved spoke pulley with discussion starting around here
http://www.modelenginemaker.com/index.php/topic,705.msg8347.html#msg8347

And here's the final pulley.  Silver soldering is involved in this one, too.


Here was my own little contribution when I machined a spoked flywheel from a blank for the pottymill horizontal engine.  This wasn't fabricated
from multiple parts, though.
http://www.modelenginemaker.com/index.php/topic,4491.msg90569.html#msg90569

It isn't quite up to the standards of the flywheels above, but I was pretty proud of it.  Here it was before it was polished up.


Holler if you have a favorite you recall and I'll hunt it down and add to this list.  But I figure I'd better post and get the show on the road!

Todd
« Last Edit: November 16, 2016, 09:32:36 PM by tinglett »

Online crueby

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Re: Fabricating a Flywheel
« Reply #1 on: November 15, 2016, 01:24:07 AM »
There was a thread or two on the jigs and setup to cut curved spoke wheels that looked great. I don't recall the exact thread, think it was one of Chuck Fellows posts? Someone here will remember which...

Offline tinglett

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Re: Fabricating a Flywheel
« Reply #2 on: November 15, 2016, 02:12:11 AM »
Chuck did indeed machine the Duclos curved 5-spoke flywheel here:  http://www.modelenginemaker.com/index.php?topic=5689.0  He had the assistance of CNC which is very cool, but something I don't have.  Nonetheless, this flywheel is quite elegant.  I agree with Chuck's post when he suggests many curve spoked flywheels are a bit gawdy.



He does reference the second book of Projects in Metal.  I don't believe this is the Home Shop Machinists Project series, but I do know the Duclos flywheel is featured in The Shop Wisdom of Philip Duclos which is published by Village Press.

Todd

Online Jo

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Re: Fabricating a Flywheel
« Reply #3 on: November 15, 2016, 09:33:21 AM »
And another soon to be fabricated flywheel: It should have been a casting but the original owner lost it  :ShakeHead:

Jo
Usus est optimum magister

Offline tinglett

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Re: Fabricating a Flywheel
« Reply #4 on: November 15, 2016, 10:10:27 PM »
Machining the Rim


My plan is to make a flywheel with a rim cut from steel pipe, a disc of steel friction fitted in the middle, a hub added to the disc, and then I'll cut out spokes and drill the hub for the shaft.  We'll see how that goes.

I started with a length of pipe procured from a friend.  He was thinking this was probably monster pipe for a building sprinkler system.  It's 4-inch pipe that's very close to schedule 40 so the thickness is a bit under 1/4 inch.  I think it'll do fine, but I plopped it into my trusty bandsaw 'cause there's no way I'm gonna cut that by hand.  But I had a little fit problem:



I should have taken the shot from a better angle, but there's no way that will cut through.   So I got a little creative in disassembling the fence and added an angle plate and some pretty big clamps:



It took a long time to saw and while it did its thing I used WD-40 as coolant.  I'd say it worked good.  All I had to do was watch.

Here's a photo of the cutoff.  It's a bit rough, but not as bad as it looks in the photo.



I indicated it in my 5-inch 4 jaw chuck.  Why a 4-jaw?  Well, my only other chuck is a 3-inch and no way would it fit.  I'm pushing the limits of my little 7x12 lathe here.  I indicated on the outside because it was quite a bit smoother than the inside due to the nice thick coating of paint.  If you look real close you can see that the rim wasn't pushed all the way against the chuck jaws.  The bandsaw cut was a little off and this is where the rim wanted to sit on the chuck.  So I went with it.  I was a little worried because I didn't want to use so much force with the jaws to unintentionally force it out of round.



I faced the rim (not shown) and then worked the outside with a cutter from the side as shown here.  I quickly ground the cutting tool for a left hand cut and it occurred to me later that I could have pulled out a boring bar for this (duh).  Yeah, I'm still a newbie.  Cutting worked pretty well, though.  The tough part was running the lathe slow enough.  With the low torque I had to take light passes.  10 thousandths was too much.  No kidding...but I made do.  Surprisingly, I wasn't getting chatter even though that tool is hanging way out there.  That's probably due to the light cuts.  I used the leadscrew for power feed since the setup was good for it.



And then the inside.  Here I'm running the lathe backward which nice to be able to do.  I was able to reach all but the last 1/4 inch or so before getting too close to the jaws.  At this point the rim is about 1.33 inches wide.  I'll do final trimming and cleanup work when the flywheel is nearly done.  At least that's my thinking right now.



I flipped it around, indicated it again (not shown), and machined it down a bit.  When I was getting close I put on some blue as shown here.  I figured that would let me see what I was doing.  And here you can see that worked pretty good.  I went until I was just starting to mess with the blue on the already machined material.



Repeat for the inside.



And there we have a rim.  The finish kind of stinks and I realized later it's because I forgot to put a little nose on my newly-ground cutter.  I'll clean it up later.  For now I'll consider the roughness a feature so I don't slip and drop it.  Yeah, that's it.  So I don't slip and drop it...



I hope to get back at it this weekend.  I want to machine a very tiny shoulder down into the middle of the rim so I can drop an oversized disc inside when the rim is hot and expanded.  But how much shoulder is enough?

Todd

Online crueby

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Re: Fabricating a Flywheel
« Reply #5 on: November 15, 2016, 11:08:38 PM »
Nice start! Watching along...    :popcorn:

Offline Don1966

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Re: Fabricating a Flywheel
« Reply #6 on: November 16, 2016, 12:03:20 AM »
Cool Todd following with interest.

Don

Offline b.lindsey

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Re: Fabricating a Flywheel
« Reply #7 on: November 16, 2016, 12:23:11 AM »
Yep, there is a flywheel in there somewhere Todd. Looking forward to seeing your progress and finding it :)

Bill

Offline Jasonb

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Re: Fabricating a Flywheel
« Reply #8 on: November 16, 2016, 07:10:56 AM »
Although this is a curved spoke pully the same methods would apply to a flywheel

http://www.modelenginemaker.com/index.php/topic,705.msg8347.html#msg8347

Also look up Jo's Crosskill build for very curved spokes
« Last Edit: November 16, 2016, 07:18:12 AM by Jasonb »

Offline tinglett

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Re: Fabricating a Flywheel
« Reply #9 on: November 16, 2016, 09:34:02 PM »
Jason,

Very cool...I added your curved spoke pulley to the first post.  I'll have to hunt down Jo's, too.

Todd

Offline tinglett

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Re: Fabricating a Flywheel
« Reply #10 on: November 16, 2016, 11:41:16 PM »
A Science Experiment

Now that I have the rim roughed out, so to speak, I'm thinking I'll machine a thin shoulder all the way down 1/8" past center so that I can drop a 1/4" thick disc that settles on the shoulder.   That seems easy enough, but I'd rather not try to silver solder the disc, but instead would like a friction fit.  But that leads to the question...how big does this shoulder need to be, how big does the disc need to be, and how much do I need to heat the rim to make it all fit?

I've got this thick little Machinery's handbook sitting here that I figure has the answer.  I'm thinking that ultimately I want the disc to be 1 or 2 thousandths bigger than the inside of the rim so it has no choice but to stay put once the rim cools down to proper size.  But I need to learn at least two things about that fit.
  • How much do I need to heat it so I can drop in the disc without getting it stuck?  Would a "free fit" calculation be the right thing for this?
  • How much shoulder is needed?  After all, I don't want to drop in the disc only to find it drops all the way past the shoulder to the bottom of the rim simply because I heated it too much!  That would be just my luck
So, hmm.  Lemme consult the book.  I have the 21st addition from 1979 and I've barely cracked it open other than to say "holy crap, 2482 pages!"  But it's a cool book with a mind numbing contents and index.  Still, it didn't take long to find Allowances and Tolerances for Fits on page 1528.   And yowsa...lots of pages of detail I'm not going to grok for a while.  It does cover shrinkage fit, which I guess is what this is, but at the moment I was more interested what is needed for a free fit so I can drop in the disc without it getting stuck.  But man, this section goes on for days and days with many tables for many things.  Ouch.

Ok, plan B.  I'll peek at my handy-dandy little machine shop tap and clearance drill size chart.  Of course this doesn't go out to 4 inches, but I'll observe that a 1 inch hole suggests 1.0156 for close fit and 1.0313 for free fit.  Ok, +31 thou.  That seems more realistic.   Looking at 1/2 inch as a sanity check I see 0.5156 and 0.5312.  So also about +31 thou.

Lession #1: I believe this means I need to expand the rim by about 31 thou.  Let's call it 40 thou.  Remember I want the disc to be +2 thou oversized so I need a little extra if I can get it.   This also means that my shoulder should be at least 40 thou total diameter increase which is a 20 thou cut all the way around.  That's getting pretty thick, but I don't think it will be noticeable on the finished flywheel and I can always machine it off later.

The numbers.  Right now my flywheel rim measures 4.087 on the inside.  If I take off 20 thou in radius (40 diameter) this will go up to 4.127.  Then for nice round numbers let's say I machine the disc to 4.130.   For this to drop in, I'll need that rim to expand to about 4.170.  What's that gonna take?

Back to Machinery's handbook.   I found a nice table called Specific Gravity and Properties of Metals on page 2270.  For carbon steel it says it'll expand 0.00000633 per degree F.  That's 6.33 millionths (thousandths of a thousandth).  Now my rim is 4.127, so I'll multiply to get 26.25 millionths per degree F.   I want this to grow to 4.170, so that's +43 thou which is +43,000 millionths.  Divide by 26.25 and I get 1638 degrees F.  Ouch...that's pretty hot!

The Experiment
Ok, do I really believe this?  For giggles, and while my wife was occupied with other things, I took the rim to our kitchen oven.  I clamped a digital meat thermometer probe to the rim and cooked it up.   This started at 76 F and I took readings up to 440 F where the thermometer became unhappy that the meat is getting way overdone.   Check out the graph of what I got:



I was having troubles with readings at the "high" end, probably because I'd have to pull out the rack and quick get calipers on it.  But I think I'm a believer that the book is right!

I quietly let the rim cool and snuck it away.  No harm done.  I think.

So...1638 degrees F for 43 thou expansion.   Sure, I can freeze the disc, but that'll only give me an extra 80 degrees tops.  I think I'm gonna have to settle for half that or so.

Isn't this fun?

Todd

Offline Don1966

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Re: Fabricating a Flywheel
« Reply #11 on: November 17, 2016, 01:05:54 AM »
I see you are enjoying the math Todd but why not just loctite it in place. It not like it's a large engine. Just saying......  by the way great presentation .... :ThumbsUp:


Don

Offline 10KPete

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Re: Fabricating a Flywheel
« Reply #12 on: November 17, 2016, 01:31:37 AM »
You really don't need a machined step in the rim. Just a spacer between the bench top and the disc.... a slug of something.

Pete
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Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Online Jo

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Re: Fabricating a Flywheel
« Reply #13 on: November 19, 2016, 05:35:10 PM »
How are you getting on with your flywheel Todd?

 :naughty:

Jo
Usus est optimum magister

Offline tinglett

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Re: Fabricating a Flywheel
« Reply #14 on: November 22, 2016, 05:20:52 PM »
Jo,

Oh, wow, no I didn't make THAT kind of progress!  :praise2:   Lemme know if you post any build log of yours and I'll add it to the list above.  Looks nice!

I did make some teeny-weeny progress that I'll post in a bit when I'm done with work today.  However, I did get other stuff done.  I finally added the air lift to my LMS mill and it was a very nice upgrade.  I'm also making a tool plate for my RT, and I think I'm gonna try to turn an MT2 to fit the RT for quick setup.   So lots of distractions.  But I promise I'll keep at this thread until it's done!    :)

Todd