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Old 18th Apr 2021, 7:25 am   #1
cathoderay57
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Default Pye 834 Flywheel Stuck

Morning all. Yesterday I started work on a newly acquired Pye 834. While it is described as a push-button set there is, as expected, a manual tuning facility that I want to get working. As you can see from the pics, the tuning flywheel is made of a Mazak or “monkey metal” alloy casting that has blown (swelled up and split) such that it is jammed against the cross-bracket through which the spindle passes. Even after removing the spring nut from the inner end of the spindle, I can’t get the spindle out. I managed to disconnect and remove the entire tuning capacitor with the flywheel still attached; it comes out as one unit. Plan B is to file down the front edge of the flywheel casting until it is thin enough to run freely, but easier said than done as the metal is tough and is resisting a coarse file. Has anybody come across a similar problem and solved it? Any bright ideas welcome. This set is well worth restoring because it is complete and other than caps replacement and dead rectifier everything else looks good. It sports a PenB4 AF pentode which should produce a beefy sound. Cheers, Jerry
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Old 18th Apr 2021, 8:26 am   #2
vinrads
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Default Re: Pye 834 Flywheel Stuck

Hi Jerry it looks kike the flywheel as actually bent the bracket , I take it the bracket is spot welded to the frame , have you removed the grub screw/screws, entirely ? try heating the flywheel hold the spindle with mole grips very tightly , and pray .Mick.
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Old 18th Apr 2021, 8:40 am   #3
cathoderay57
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Default Re: Pye 834 Flywheel Stuck

Hi Mick, thanks for the tip. Yes, spot welded and I have fully removed the grub (actually standard) screws. More application of the Armstrong method this morning has filed off about 0.5mm which is enough to allow the flywheel to rotate but it is still rubbing slightly at the edges of the bracket on account of the curvature. I'll have another go when my wrist has recovered and hopefully that will be enough. Wish I had a dremil! Cheers, Jerry
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Old 18th Apr 2021, 8:43 am   #4
Gabe001
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Default Re: Pye 834 Flywheel Stuck

Jerry you've done the work already, but you can get grinder bits for a standard drill if I'm not mistaken
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Old 18th Apr 2021, 8:46 am   #5
FIXITNOW
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Default Re: Pye 834 Flywheel Stuck

Flywheels are not uncommon if it was mine i would take the angle grinder to it and fit another flywheel
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Old 18th Apr 2021, 8:46 am   #6
Gabe001
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Default Re: Pye 834 Flywheel Stuck

Something like the attached.
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Old 18th Apr 2021, 9:18 am   #7
Radio Wrangler
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Default Re: Pye 834 Flywheel Stuck

That flywheel is a zinc alloy diecasting and it's got the lurgi. THe metal has changed and is breaking up. The only way forwards is to fit a new one. The flywheel itself is of no further use so cut it up to get rid of it. It shouldn't be difficult, the alloy has gone crumbly and is already breaking itself apart. Withe the flywheel gone, the shaft should be easy to remove. The swelling will have gripped the shaft with remarkable strength.

As for a new one, you'll need a friend with a lathe, and a chunk of iron, steel or brass, some sense metal.

With a bit of luck, the bracket might bend back into shape. The main difficulty is in not damaging anything else while you're getting aggressive with the old flywheel.

Grinding stones are not likely to be much help as they tend to clog their pores with soft metals. Try drilling a lot of holes... it should fall apart for you. Take care not to damage the shaft, aim your drills to miss it. Hacksaw blades can be useful with insulation tape wound on to make a handle. Have the teeth the right way round to cut on the pull stroke.

Coarse files are another possibility but you'll need to keep carding them as they clog.

David
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Old 18th Apr 2021, 8:11 pm   #8
cathoderay57
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Default Re: Pye 834 Flywheel Stuck

Thanks everyone. In the end, I managed to file off sufficient material to get the flywheel to turn. I don't have friends with lathes but maybe in future I'll look at it again; for now I'm content to have the set such that I can tune it. The flywheel looks bad but isn't in immediate danger of breaking apart and inside the set nobody is going to see it. Now for the fun bit doing the electronics. When I get it going I'll do a success story. Cheers, Jerry
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Old 6th May 2021, 3:19 pm   #9
cathoderay57
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Default Re: Pye 834 Flywheel Stuck

Well, the radio performed very well as described in success stories. Unfortunately the flywheel has jammed again and the threads on the cheese head "grub" screws have stripped. There was nothing left to do except have another go at removing the flywheel. I did try drilling it to death as suggested earlier but the alloy, although brittle in places, is incredibly hard to drill. After about 5 minutes the drill bit had penetrated only about 5mm. I would have been there for a week. I removed the locking nut and spring again from the inner end of the spindle and gave it a good pull with mole grips but still no joy. It would pull out about 5mm then it felt like it was hitting a stop. I decided to have a go at breaking up the bush at the centre. I did this by forcing in an oversize screw into the grub screw holes. Luckily a large chunk of Mazak broke away exposing the outer edge of the spindle. I could then identify the problem, which was that the grub screws had pointed tips that engaged in a couple of punched locating points in the spindle surface. The raised burrs around these points were preventing the spindle from sliding through the hole in the outer cross-bracket. I attacked the burrs with a needle file and the spindle came out with ease, allowing the knackered flywheel to drop out. I have found a flywheel on eBay that I might be able to persuade to fit. Failing that I'll put the dimensions in the wants section and also a request in services wanted to see if anybody has either a spare or a lathe and can turn me a replacement. Cheers, Jerry
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Old 10th May 2021, 11:09 am   #10
cathoderay57
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Default Re: Pye 834 Flywheel Stuck

That's better!
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Old 10th May 2021, 11:20 am   #11
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Default Re: Pye 834 Flywheel Stuck

Superb Jerry glad you found a suitable replacement.
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