BSR plastic or metal cycle cam?

[hayerjoe]

hello everyone

I had a 1970s BSR deck who's pivot for the cycle cam had become quite loose, probably due to the grease acting like a a glue, so it ended up turning the entire riveted-on pivot rather than the cycle cam turning around the pivot

Anyway was bored so thought I'd try and fix it, just to see if it's possible. first attempt was soldering it from below, needs a lot of heat and it didn't last very long. So next I tried hammering a large Philips screwdriver bit into the loose rivet (photo - not actually the pivot rivet but exactly the same so you get the idea). The 4 points on the Philips bit created 4 lock points in the rivet and it seems to have worked very well

but now my question to the forum...

I think its fixed but I don't want to over stress that pivot, so I want to fit a nicely lubricated cycle cam to it. But which when greased would generate the least friction, an alloy cycle cam or a plastic cycle cam?

I see pros and cons in both. The alloy cam hole would have been drilled so maybe that's very smooth and precise whereas the plastic one would be straight from the mold so could be tight. Under a microscope would metal be rougher but accept and retain grease better than a plastic hole?

what do people think?

[Silicon]

The alloy part looks like a diecast component. There are many lubrication options.

Mineral oil based greases can degrade plastic components.

[hayerjoe]

not many comments but quite a niche subject!

i decided to go with the plastic cycle cam and white lithium grease, not because I thought it had the least friction, but more that when I come back to this deck in 6 month's time I'll think "why did I put that white plastic cycle cam in there, oh yes, better key an eye on this one"

[unitaudio]

I think plastic or metal would be equally ok as long as the grease isn't allowed to dry out again. In any case, that would take years to happen.

Regards,
Paul

[hayerjoe]

if it dries out again then the plastic cam will be a massive liability as I needed to apply a full-on blow torch to the orginal metal one. Plastic ain't gonna like that!

[PaulR]

I have a Sansui semi auto deck which uses a similar arrangement. The cam set up is plastic and it runs very smoothly, much more so than the BSR diecast type. That may be because it is more finely made but if I had the choice in a BSR deck I also would go for the plastic cam. Of course it will get more wear in a full autochanger but other items with plastic gears last for a very long time.

I never thought I would choose plastic over metal but in this case the plastic seems better.

[hayerjoe]

Originally Posted by PaulR

I have a Sansui semi auto deck which uses a similar arrangement. The cam set up is plastic and it runs very smoothly, much more so than the BSR diecast type. That may be because it is more finely made but if I had the choice in a BSR deck I also would go for the plastic cam. Of course it will get more wear in a full autochanger but other items with plastic gears last for a very long time.

I never thought I would choose plastic over metal but in this case the plastic seems better.

and you'd have to think plastic would be a bit queiter

[PaulR]

Regarding lubrication, the turntable bearing was pretty dry and it didn't run freely until lubricated but the auto cam was totally free

[slidertogrid]

It looks as if the cam has been fouling the base plate was that because the spigot was loose? Have you made sure the 'peg' that runs in the cam is completely free to rotate? Also I notice the tiny ball bearing is missing from the trip pawl actuator lever have you replaced that?
It should work fine with either cam the cast ones are far more common and are fine I think the plastic cam was used on the later 'cost improved' deck.

[hayerjoe]

Originally Posted by slidertogrid

It looks as if the cam has been fouling the base plate was that because the spigot was loose? Have you made sure the 'peg' that runs in the cam is completely free to rotate? Also I notice the tiny ball bearing is missing from the trip pawl actuator lever have you replaced that?
It should work fine with either cam the cast ones are far more common and are fine I think the plastic cam was used on the later 'cost improved' deck.

That's a very good point, yes it was so loose it must have been scraping the base plate, another reason to go with the plastic cam I think, but I'm fairly certain I have the pivot nice and square now

Yep the ball has been removed for safe keeping, in fact to get at the back of the pivot to re-set its rivet you have to remove the trip pawl slide and ball

I've no idea where I got the plastic cam from, just in a box of spares I think, but I think they are quite rare (for the BSR cycle cam collector out there!) as was probably the last cost cutting "innovation" before they went to using belt drive

[mister valve]

When I worked in a factory making "music centres" & "Record players" (amongst other things), we used mainly BSR record decks. When I first saw them come to us with plastic cams, I cringed, and thought to myself "how long do they think they will last before the teeth are chomped up, or the heart-shaped cam takes on a different shape".

Well I have to admit, I worried over nothing.... they have done very well ! Apparently, they were made of a very strong 'Nylon' type material, and I've never heard of one getting damaged through wear.