Advice on machining PM Research 6 ½ inch flywheel (No:1Bi).

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Sandown62

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Advice on machining PM Research 6 ½ inch flywheel (No:1Bi).
Hello,
Has anybody machined the 6 ½ inch flywheel for PMR engine 1BI? Just wondering what your process was as I would like the wheel to run true when finished..I have a 4 inch three jaw chuck on lathe……Thanks!
Stephen.
 

Philjoe5

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Welcome Stephen,
Before I answer your question it would be helpful to know what machines you're using and some background on your experience in model engineering.

Phil
 

Jasonb

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Also is that your only chuck or do you have a 4-jaw and/or a faceplate
 

rhankey

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I personally rough turn the flywheel, bore the hole for the crankshaft and optional keyway, then turn it to final dimensions while it is mounted to the crankshaft as it would be normally. If the crankshaft is too unwieldy to mount in the lathe, then use a piece of scrap that serves as the crankshaft. It would be better if you can use a collet to hold the crankshaft or a 4 jaw chuck so you can ensure the crankshaft is turning true.
 

lensman57

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Advice on machining PM Research 6 ½ inch flywheel (No:1Bi).
Hello,
Has anybody machined the 6 ½ inch flywheel for PMR engine 1BI? Just wondering what your process was as I would like the wheel to run true when finished..I have a 4 inch three jaw chuck on lathe……Thanks!
Stephen.
If you have a small drill press, find the center of the wheel, spot, center drill, drill undersize and ream to size . Then make an arbor just undersize to the bore of the wheel making sure that it is a tight fit with a small shoulder at the back for the wheel to butt against, thread the front bit and mount the wheel ( do not take the arbor out of the chuck under any circumstances ) and secure with a small washer and a nut and machine, reverse the wheel to finish off the other side if necessary. You may have to finish the face with a file if the nut doesn't allow you to machine the face. You can also make an expanding mandrel for the wheel, it is almost the same procedure as before but you cut slits in the front of the mandrel, deep center drill it drill for tapping a small machine screw. Once the screw is turned it will force the slits open inside the bore and locks the wheel. This is a little more involved but works better. The inner face of the screw has to be machined first to match the angle of the center drill, 60 degrees?, and then you get on with the rest. Another lazy way is to just machine the arbor to the bore size, put a little loctite on the arbor and secure the wheel, once it is cured it won't move, after machining you can release the loctite by heating the hub, clean up and repeat for the otherside.

A.G
 

Sandown62

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I do have a four jaw chuck however, I dont think it'll hold the wheel and enable me to turn the outside and face it off ...and drill the center. looks like my best option is to use the arbor method. i can see how drilling the center hole first and holding the wheel by the arbor should leave me with a nice true running flywheel !
 
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