HMV 102 Spring Length

[2E1CIH Mike]

Hello,

Could anyone tell me the correct spring length for a 1936 HMV 102 (270D motor) please?

I have painstakingly measured the original one, using a piece of wire, and it appears to be 13ft 4ins long. This one was broken at the outer end.

I have been supplied a new spring which is 15ft 6ins long. The supplier said it is longer than the standard one.

When I re-assembled the motor with the new (15ft 4ins) spring, it seemed to be binding and wouldn't run. Could this be due to the new spring being too long please?

Many thanks.....Mike

[Techman]

I can't see it making any difference. If it winds up it should work. I've never fitted an actual new replacement spring, I always repair the original if I can. Are you absolutely sure you fitted it the correct way round? It won't be the first time that I've heard of someone fitting a spring incorrectly.

[2E1CIH Mike]

Hhhmm. I must admit that has crossed my mind.

From memory, I wound it clockwise from the outside inwards. However, I think it wise I check this.

Thanks for your reply.

[2E1CIH Mike]

Having said this, I have wound it seven turns. Would this be possible if the spring was in the wrong way round? I wouldn't have thought so.

[Techman]

The last one I did was in a 101 and that wound in clockwise from the outside in, so your motor is likely to be the same, but if in doubt there's probably some pictures out there on-line that may show the innards of your type and model.

If it was in the wrong way round it would probably wind it backwards for a few turns before it went 'ping'!

You really ought to take photos or at least make notes on how things were originally fitted.

It's possible that the spring is too wide, so I would be checking the width of both new and old.

There's a question over the quality and reliability of recently manufactured springs at the moment and this is a world wide problem and nothing to do with any of the suppliers, who possibly get their supplies of springs from one source somewhere in the world - place unknown to me at the moment. I've personally suspected that this has been a problem for a number of years now because of the number of documented failures of brand new replacement springs. My suspicion is that the ends are not fully re-tempered properly after they're made, hence why I prefer genuine old stock or to repair the originals. Sometimes there's no choice other than to buy a new replacement.

I certainly wouldn't be disposing of your original broken spring just yet, as you may end up having to repair and reuse it.

[2E1CIH Mike]

Thanks for your comments.

I normally do take lots of photos and make notes. I probably didn't take one of the spring before I took it out because I was preoccupied with the danger aspect of the job.

I will start from scratch I think. I'll use a vernier to measure the width of the old and new springs.

I've seen somewhere that the spring should be just over 14 ft long. If I repair my original, I'll probably lose a couple of inches so it will end up about 13 ft 2 ins. Would you say this will affect its performance?

Also, should the end be tempered or annealed......or neither?

Thanks.

[af024]

Not that this is likely to be your problem, but in the interest of sharing my experience with replacement springs, I had a replacement which, when fitted, the motor wouldn't even provide enough umph to play one side of a 10" 78! The spring had all the right dimensions, was suitably lubricated (as was the rest of the motor) and fitted etc, so I came to the conclusion that the spring material wasn't as stiff (is that 'Young's Modulus'?) as the original. I wonder how this can be checked and compared?

[2E1CIH Mike]

Hi af024,

Thank you for sharing your experience. That's interesting. It makes me think I may have wasted money buying a new spring.

I think that, due to the nature/shape of the spring, it would be difficult to test springiness. Maybe the fact they were each installed, and their performance differed is proof enough.

My original spring was broken at its outer end. It would be fairly easy for me to drill two different sized holes and file between them to create the necessary end to locate onto the rivit on the outer part of the barrel. I'm not sure if I'd need to anneal this repair though. I'll research the net.

Yes. I recall that Young's Modulus is related, as is Hooke's Law. My memory still works!

Regards....Mike

[2E1CIH Mike]

Hello Techman,

I measured the width of the springs with a vernier.

The original one is 25.4mm and the new one is 25.1mm.

It would have been more useful if it had been the other way round but the new one is 0.3mm narrower.

Later in the week, I'm going to have a try to repair the original one. That used to work to a small extent. As it was broken at the outer end, it would only wind a little before it slipped.

If it works with the repaired original one, I will conclude that the new spring doesn't work because it is a couple of feet longer.


Regards......Mike

[af024]

We look forward to your update Mike - an interesting post!

[Techman]

Originally Posted by 2E1CIH Mike

Later in the week, I'm going to have a try to repair the original one. That used to work to a small extent. As it was broken at the outer end, it would only wind a little before it slipped.

Just remember that after the so called annealing to remove the existing tempering, that after you've re-made the end you'll have to then re-temper the end by heating and quenching, otherwise the metal will be too soft and won't last long. I think that this is some of the problem with the new replacement springs that seem to fail, particularly on the inner end. I've recently heard a report from an American chap who does repairs and also sells gramophones that he's just had a 'come back' from one he recently sold that he'd fitted a new spring to and which had failed after not a lot of use. Apparently, when he opened it up he found that the 'hook' on the inner end of the spring had completely flattened out. This instantly tells me that the metal at that end of the spring had not been re-tempered at all, probably because it's difficult to do at that end.

[2E1CIH Mike]

Yes. Good point Techman.

I've had some success. I think the problem must have been due to the spring. I have re-fitted the original one after repairing it's outer end and it runs fine again.

I could see from "bluing" that my repair was on the tempered part so that should be fine.

I've given it ten winds and the only problem I have yet to solve is that the spring barrel sheds its spring clip. I spent about 90 minutes faffing with that yesterday. I'm thinking either the clip or barrel aren't completely round. The motor spring is definitely seated properly and the clip goes into the groove everwhere but there's always one segment where it won't seat.

I have an idea to get a proper internal circlip. I think it needs an 88mm one. A quick look last night revealed that sizes like this are available.

I'll report back. Mike

[2E1CIH Mike]

I've had another go.

I think Techman is right. The barrel clip fits into a swaged groove which isn't a particularly good design. Most spring clips fit in, or around something machined. This is more like sheet metalwork.

An 88mm circlip is 3mm thick and I doubt it would fit into the swaged groove, even if it was ground, so I have carefully tapped the swaging round a bit more to try to keep the clip in. It looked better and I applied locktite all the way round for added security.

Loctite takes 24hrs to cure so I'll leave it a couple of days to make sure.

I'll report back.