Author Topic: 600 x 25mm disc  (Read 3359 times)

Offline redshift

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600 x 25mm disc
« on: December 05, 2012, 05:49:41 PM »
My lad is into kart racing and is quite competetive, I am the one who gets to do all the jobs other than driving the kart.  We are looking to gain an edge on engine performance and we plan to build a dyno to optimise our engines. The dyno will be of the inertia type and the electronic interface will be DIY employing an Arduino Package.
The key to this working accuratley is by matching the inertia of the flwheel to the weight and acceleration of the kart and this is why we need a 600 x 25mm steel flywheel.
My lathe can only manage 300mm od. so I was thinking along the lines of machining the od, 40mm bore and 6 x 10mm holes on150mm pcd, all at one hit using a 12" rotary table on my bridgeport.
Can anyone forsee any problems doing this, especially the od.
Regards
Dave

Offline PekkaNF

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Re: 600 x 25mm disc
« Reply #1 on: December 06, 2012, 05:12:24 AM »
Circular milling is pretty normal and should work. Setup is pretty critical here it must be pretty true and rigid, othervice you will make something wobbly.

Can you first machine (other side) true surface and mounting surface that will mount on rotab. You may consider making an inser with lathe, that will allow you to mount this embryo fly wheel on rotab and provide clearance for drilling.

Mount the insert and "disc" it straight and without twist on rotab and then machine "the other" side, holes, and all on one go?

I don't know what rpm you are looking at but you need to balance this. Static balancing might not be enough. What kind of mounting you are thinkking? Mount must be pretty solid. Sometimes bushings made with best possible home work shop accuracy come out just enough exentric that will allow some adjustement when turned in relation of each others to minimize errors.

Pekka

Offline BillTodd

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Re: 600 x 25mm disc
« Reply #2 on: December 06, 2012, 06:03:21 AM »
Have you considered a heavy using a flywheel (or two)  from a car/truck engine? (already round and well balanced)



BTW just from a safety point of view - have you calculated stresses on the flywheel at max rpm?   600mm @ say ~10,000rpm could be 'interesting' :)



Bill
Bill

Offline redshift

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Re: 600 x 25mm disc
« Reply #3 on: December 06, 2012, 06:07:42 AM »
Pekka, thanks for the reply.
I was hoping to find some ground 25mm plate to use, I know it will cost plenty but it should save the machining of the faces of the flywheel. My initial thoughts were to mount onto rotary table with a piece of 6mm ali plate underneath to enable through drilling.  This is a much bigger piece than I have done before and any suggestions on cutter type and size would be appreciated. Are there likely to be any vibration problems during machining with 150mm the flywheel overhanging the edge of the rotary table?
 The finished item will be mounted with a taperlock bush onto a 40mm shaft supported by a couple of suitable plumber block bearings, the taperlock assembly will also be keyed onto the 40mm shaft, I can cut the flywheel keyway on the Bridgeport as there is a shaper attachement fitted to it.
Between the two plumber blocks are the flywheel and a disc brake which is used to slow the flywheel down after the test run.
The engine will rev to 15k rpm and with a 6:1 reduction the flywheel will do 2.5krpm so there is a lot of inertia in the flywheel and without the brake it would probably take 15 mins or more to stop.
So if you can give me a bit of guidance on what cutter to use especially on the od. that would be great.
Regards
Dave

Offline BillTodd

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Re: 600 x 25mm disc
« Reply #4 on: December 06, 2012, 06:20:59 AM »
Quote
Are there likely to be any vibration problems during machining with 150mm the flywheel overhanging the edge of the rotary table?
Plenty !

You may want to clamp a piece(s) of plywood to the disc to damp the vibrations and support the edge you're cutting with jack and something slippery.

You can clean-up the diameter once its mounted in the pudding blocks with careful use of a grinder.

Bill


P.S.

Running a land-speed record  Vincent on the dyno - you must watch this! (interesting dyno)

http://www.youtube.com/watch?v=NQIhqazUHg8&list=UL

Bill

Offline doubleboost

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Re: 600 x 25mm disc
« Reply #5 on: December 06, 2012, 04:00:29 PM »
I think i would have had a thick lump of plate between my chest and that engine :jaw: :jaw: :jaw:
John

Offline BillTodd

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Re: 600 x 25mm disc
« Reply #6 on: December 06, 2012, 04:51:07 PM »
Sorry this is the one with a description of the dyno:

http://www.youtube.com/watch?v=Zw6hhAmzXQs
Bill

Offline RadRod67

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Re: 600 x 25mm disc
« Reply #7 on: January 31, 2013, 07:52:25 PM »
Have you considered an off the shelf cast pulley? 640mm od is a std size
Regards,
Rod.

Offline redshift

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Re: 600 x 25mm disc
« Reply #8 on: February 01, 2013, 05:41:13 AM »
Rod, thanks for the link.
I will do a few calcs regarding the inertia of the pulley and the 2,000 rpm safety requirements.
If all ok it would be a quick but probably expensive solution.
Regards
Dave

Offline The Steamer

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Re: 600 x 25mm disc
« Reply #9 on: February 01, 2013, 05:17:39 PM »
Id find yourself a local laser cutter! some bits ive just had cut were about 8 more than itd cost me to buy the sheet and cut them myself! They were that good a 3 thou cut cleaned the O.D! Itd save you alot of work and leave very little to machine afterwards.

Offline vtsteam

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Re: 600 x 25mm disc
« Reply #10 on: February 01, 2013, 10:02:08 PM »
What about a large arbor as a temporary lathe?

Even oiled split hardwood bearings would work for a one-off job like this. Drive it at a conservative speed and if you are only truing the rim you can use a plain hand steady rest and a simple graver.

Facing is more of a problem, you then need a slide -- though not necessarily impossible to rig.

I love it when a Plan B comes together!
Steve
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