How to machine a flywheel ?

[Brian JohnParticipant @brianjohn93961]

Woops, I realised that I have posted in my other thread about the lathe ! I meant to post here.

The aluminium flywheel was completed today by holding the hub in the chuck to take a facing cut on the hub and drill out to 6mm. Once this was done I fitted a steel mandrel and machined the outer rims and the main outer surface. It has worked out okay because there was enough hub to grip with the chuck. A smaller/shorter hub and a face plate would have been necessary.

The video above was interesting but he did not use an etch primer before painting the flywheel. I would not expect the paint to stay on very long without an etch primer ? I always use two coats of etch primer before painting.

 

 

Edited By Brian John on 04/10/2015 15:08:01

[Brian JohnParticipant @brianjohn93961]

I have been digging into my box of flywheels to see what I could do with them now that I have steel mandrels to work with. The smaller wheels can be gripped from the outside of the rim, the larger wheels can be gripped from the inside of the rim and some of the wheels can be gripped by the hub if nothing else will work. I am getting a very good finish using the mandrels.The photo bellows shows four wheels that have been machined (top row), two wheels which can be machined (middle row) and one wheel (bottom row) which will need a face plate as there is no hub to grip.

But I have one aluminium flywheel (last photo) mounted in my lathe now which is giving me some unexpected problems. There was a large hub to grip so after getting it to run true in the chuck, I faced off the hub and drilled out to 6mm. But when the mandrel was fitted to begin machining the outer edges I am getting a ''fish scales'' pattern accompanied by a bell-like ringing sound. I have not come across this sound before. I have adjusted the speed higher and lower and I have changed tools. I have also tried different angles for the tool but nothing seems to work. Any suggestions ?

UPDATE : the wheel makes that ringing sound even when I strike it lightly with a wooden paint brush. Perhaps this wheel is the perfect size for vibrating which is making it awkward to machine using a mandrel ?

 

Edited By Brian John on 05/10/2015 06:35:47

Edited By Brian John on 05/10/2015 06:38:09

Edited By Brian John on 05/10/2015 06:47:05

Edited By Brian John on 05/10/2015 06:47:52

[JasonBModerator @jasonb]

The tool is chattering at a high frequency which is the ringing you can hear and the cause of the patterned surface. Basically the flywheel being larger than the others is not supported enough and is flexing away from the cutting tool.

Try slowest speed, very fine cut, very sharp tool.Use the tailstocj ctr to support the mandrel

Edited By JasonB on 05/10/2015 07:56:53

[Brian JohnParticipant @brianjohn93961]

I have tried everything except the tailstock centre (I should have thought of that…thank you ) . I have to take my wife somewhere now but I will give it a go tomorrow.  I really think that this one will need the face plate.

Edited By Brian John on 05/10/2015 08:04:20

[MichaelRParticipant @michaelr]

You could make a Plywood/Chipboard faceplate to fit your mandrel and back your flywheel onto the wood faceplate by lightly clamping the flywheel by the spokes, this should stop the chatter as mentioned by Jason.

I used this method when I did the flywheels for my Wyvern and Centaur gas engines.

Mike.

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

I think Jason's advice will see you through the immediate problem; but I would just like to say that "fish scales" was probably the best graphic description I have seen for chatter marks.

MichaelG.

[Gordon WParticipant @gordonw]

I made a "faceplate " for my lathe just to do jobs like yours. A short piece of pipe or bar, say 20-30 mm dia. skim the outside and face square, weld a round or square plate to the faced end. Put the bar in the 3 jaw and skim the face flat. Scew or bolt a bit of ply or mdf to this and then skim the wood if needed. The flywheel can the be fixed with bolts and clamps or whatever is suitable. Not hugely accurate but ok for these sort of jobs and can be skimmed again if needed.

[Michael CheckleyParticipant @michaelcheckley34085]

Mine runs ok having used this method…..

[Brian JohnParticipant @brianjohn93961]

I used the tailstock centre and that helped a bit. I decided I would machine the main outer surface first. After I did this the outer rims machined much more easily. Perhaps it was because the wheel was now more balanced.

I also have the same flywheel in brass and this was even more difficult. I used the tailstock centre, machined the outer surface first but nothing was working. So then I changed tools and used a sharper angle on it. I also slowed the chuck speed right down. Once I got the outer main surface finished I then finished the outer rims. It eventually turned out well.

I have now machined six flywheels and only two more flywheels (both brass) to go. A couple of them are not good castings ie. there are some small air bubbles in them but they were cheap and it is good practice.

[Ian S CParticipant @iansc]

If the ones with holes are brass or cast iron, save the fine chips and mix them with epoxy glue, fill the holes with like metal and you'll hardly see them, or just use poly filler and paint them.

Collect old ball or roller bearings, pull them to bits, they are good for parallel packing behind flywheels etc.

Ian S C

[Brian JohnParticipant @brianjohn93961]

''Parallel packing behind flywheels'' : sorry but you have lost me there ?

[JasonBModerator @jasonb]

Brian if you look closely at Michaels first photo you will see a ring behind the flywheel just inside the three fixings packing it out from the faceplate. The idea is that you support one side of the spokes as close to the bolts as possible and clamp on the other side which avoids distorting the flywheel if it were only the rim against the faceplate.

It also allows you to machine the whole of the outer face without running the tool into the faceplate

Edited By JasonB on 06/10/2015 16:07:57

[Brian JohnParticipant @brianjohn93961]

Thank you, now I understand about parallel packing.

Why is there tape on some of the spokes in that photo ? The tape does not seem to be doing anything. It is not on every spoke.

He has also taken a cut around the hub. I guess that is optional ?

Edited By Brian John on 06/10/2015 18:16:58

[JasonBModerator @jasonb]

I would hazard a guess that not all of the spokes were touching the packing ring as castings are seldom perfect, a few winds of take will thicken them up a bit so all six contact the packer. Tape in the second photo is so the jaws don't mark the finished flywheel

[Brian JohnParticipant @brianjohn93961]

Now that I have drilled eight aluminium and brass flywheels I have noticed that my drilled holes seemed to be getting smaller ! The steel mandrels that were a good fit at first are now too tight. How can that be ? Surely the drill bits cannot be wearing ?

Once I have got the flywheels running true in the chuck, my procedure is as follows. I either grip the outer surface, inner surface or grip the hub ; on a small lathe like this you take whatever is on offer. The largest flywheel I can machine using this method is 80mm diameter as the cross slide will not come out any further.

1. facing cut on the hub

2. spot drill 3mm about half way through the hub

3. 3mm jobber drill all the way through

4. spot drill 6mm about half way through (perhaps not necessary)

5. 6mm jobber drill all the way through

6. finish off with a 6mm H7 reamer (doesn't seem to be doing much at all ?)

7. turn over and face off the other side of the hub

8, fit steel mandrel and machine outer surface of flywheel

9. machine the two outer edges

10. tidy up with a small file along all the sharp outer and inner edges.

Would an adjustable 6 to 6.5mm reamer be a wise purchase at this point ?

 

Edited By Brian John on 08/10/2015 07:29:50

Edited By Brian John on 08/10/2015 07:30:12

Edited By Brian John on 08/10/2015 07:30:48

[JasonBModerator @jasonb]

We told you earlier that you need a drill smaller than the reamer, 5.8 would be about right. That way the reamer can actually do some work and cut an accurate hole.

[Brian JohnParticipant @brianjohn93961]

My Bergen engineers drill bit set in 0.1mm increments arrived only recently. I have not used the 5.8mm or 5.9mm drill bits yet…I forgot they were there ! The hole I am getting is slightly too small compared to what I was getting a few days ago. Had I been getting slightly too big a hole I would have started using the 5.8 or 5.9 drill bit and reaming up to size. But if the hole I am getting is a bit small then I am not sure how using the 5.8 drill bit would help ?

I will try it tomorrow on some scrap aluminium I have.

[Michael CheckleyParticipant @michaelcheckley34085]

Sorry, forgot to mention the packing. What you can see behind is a bearing inner race being used as a spacer that I had thrown in the 'come in handy' box. Jason is correct the tape on the odd spoke is because all the spokes didn't sit flat against the spacer.

If I did it again I would pay more attention to how well the inner of the outer ring (between the spokes) of the casting was running true rather than the central hub as the outer ring is more obvious if it is not running true, or if I had found there was not enough hub material to clean up find a better compromise.

[Brian JohnParticipant @brianjohn93961]

I am considering the cast iron flywheel that came with my Stirling engine kit from Bergs. I will need a face plate to machine this as I doubt that facing off the hub and drilling out to 6mm will work on cast iron by holding the hub in the chuck.

Why do they cast flywheels in cast iron at all ? Brass looks better and is much easier to machine.

[Bodger BrianParticipant @bodgerbrian]

Posted by Brian John on 09/10/2015 08:10:46:

Why do they cast flywheels in cast iron at all ? Brass looks better and is much easier to machine.

I'm going to stick my head on the block & say that cast iron is more prototypical, and as such will look better. The question of which is easier to machine is immaterial.

Bodger Brian

[JasonBModerator @jasonb]

100% agree with brian, not only is it the right material it looks correct on an engine that had a bare rim for beltwork, many had their flywheels completely painted if they had a separate pully or were not used for rotative work.

You can always polish up a cast iron rim to match any other bling on your engine, it does come up quite well if needed.

[roy entwistleParticipant @royentwistle24699]

As well as thje cost

[Rod NeepParticipant @rodneep80388]

I just found this thread as I am working out the same problem….

The problem arises with small spoked flywheels such as the 3" one on the Stuart S50.

1. The faceplate on my Warco WM240 is massively oversize for this task, and there is no way to mount the cast flywheel onto it. (The hole in the centre of the faceplace is 2" diameter! so there isn't any way to drill it to take clamps to fit onto the flywheel being turned)

2. It isn't possible to grip the inner diameter of the flywheel rim because the jaws on the chuck won't fit through the spokes. (Neither will the jaws on a small chuck fit between them)

3. It is possible to grip a part of outer diameter of the rim in large outside chuck jaws so that the centre boss can be machined to accept a mandrel, but : a) only small part of the rim is held, and b) it just isn't stable enough on the rough casting face. (It is also just about impossible to get the cast iron flywheel to run anywhere near true).

4. gripping the small boss of the cast flywheel in a 3 jaw or 4 jaw chuck is a non-starter.

THE SOLUTION:

I bought a small faceplace (actually it is designed to fit a small Emco lathe) : 80mm faceplate threaded 14x1mm (RDG Tools ref: 2866 – price £18.30). And also a 3MT Arbour 14x1mm with a 12mm drawbar (RDG Tools ref 873459 – price £12)

So now I can mount the new small faceplate onto the 3MT arbour, and fit it direct to the spindle of the lathe. It isn't a cheap solution, and I hope that I will be able to use it for other jobs in the future, but the set up enables me to clamp the small diameter flywheel by the spokes for turning it the "correct" way.

Rod

[mechman48Participant @mechman48]

Posted by Rod Neep on 11/04/2016 12:36:40:

I just found this thread as I am working out the same problem….

The problem arises with small spoked flywheels such as the 3" one on the Stuart S50.

1. The faceplate on my Warco WM240 is massively oversize for this task, and there is no way to mount the cast flywheel onto it. (The hole in the centre of the faceplate is 2" diameter! so there isn't any way to drill it to take clamps to fit onto the flywheel being turned) …

I have the same upcoming problem… The faceplate for the WM250 is weighing in at 5kg… some piece of C.I. to have going round even at a moderate 260 rpm… plus any clamps fitted. I utilised an aluminium face plate that I made up some time ago & it works out just fine, fitted & machined the standard ok so will suit the flywheel, will have to add more tapped holes to suit though but will check balance it first…

Home made faceplate & clamps, so should suit the flywheel admirably…

George.

[Neil WyattModerator @neilwyatt]

Brass flywheels make models look like models more than anything else, IMHO.

Cripes George, i still have the clamps I made to do that to my 10V – they are only 1 1/4" long and 1/4" thick!

Neil

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