Drawing for 280 large fibre gear?

[Pete.]

Hi guys, in the headstock of my 280 synchro there is a large fibre or nylon gear which the selector fork slides to and fro when selecting high/low speeds. The teeth on my gear are machined away from ham-fisted gear changes and offers only a small amount of engagement, I think it's only a matter of time before it strips completely so I'd like to get a replacement made before I have to strip the machine down. Any chance there is a drawing for this gear in the archives?

Looking at the 280vs headstock arrangement there is a similar-looking gear, drawing BVS100/105. I haven't found an arrangement drawing for my 280 synchro but my lathe does have an un-used toothed wheel that the VS uses for rpm signal so I thnk it's a fair bet they are the same.

Pete.

[Andy B]

Pete,

Hopefully the GA and part drawings are in the collection that I now have to scan - but it may take a while to get to them.
Send me a PM in a couple of months if I haven't replied before then.

Andy

[Pete.]

Thank you Andy, I will. I'm sure it will last a few months at least.

P.S. if you happen to come across drawings for steady and following rests for the 280-series I would be really happy about that too.

Pete.

[Andy B]

Pete,

I've got copies of the drawings for the steadies readily accessible - making a pattern to get some castings done has been on my 'to-do' list for a long time.
Are you interested in a joint venture project?
I'll dig the drawings out next week.

Andy

[Pete.]

Yes indeed Andy, I could make some moulds for casting or produce cad drawings to have them cut from steel by waterjet.

These seem to be rarer than hen's teeth.

[Andy B]

Found the Synchro parts list and it confirms the headstock internals to be the same as the 280VS.
Now just have to locate drawing BVS100/105 ....... I think I should have it somewhere!
Andy

[Andy B]

Here you go - The DP of the gear was changed in 1978 from 10 to 12.
I believe the Synchro range were all later than this, so should all be 12DP but I'm sure you'll check the number of teeth first.

I can't find any reference to the exact material - Technyl A 90 - on the web, but I expect the techical department of the manufacturer (Rhodia) should be able to tell you the current equivalent in the Technyl range.
Please post it here if you find out, as there were several parts made from this material.

Andy

[Pete.]

Andy - thank you very much indeed! I'll do some research on the material and make enquiries on any possible suitable equivalent.

Incidentally, the second download link in this sticky-post is a full parts list for the Synchro:

viewtopic.php?f=50&t=2961

Pete.

[Pete.]

Just a follow-up, I haven't had a reply yet from Rhodia regarding the material bu tI did get a quote from a gear manufacturer who quoted the part made from Delrin Acetal.

[Andy B]

Pete,

Just for reference, do you mind sharing how much the quote was?
I assume this was to make from scratch rather than from a supplied turned blank?

Andy

[Pete.]

To make it from a drawing they quoted £270. Needless to say, I will be investigating other options.

[Pete.]

Well since my own gear is on it's way out and Rocboni's is missing a bunch of teeth, and neither of us want to pay £270 a piece I've decided to collaborate with him to make us both new gears. We're each buying our own material, Rocboni's paying for the involute cutter and I'm doing the work.

Here is the first blank finished to size and test-fitted to the hub from Rocboni's lathe. Having the parts in my hand made it a lot easier for me since I'm not an experienced machinist and found it easier than trying to visualize the work from the drawing, being able to test-fit the parts means that I could get a very nice fit too.

65tgear.jpg (59.67 KiB) Viewed 12887 times

Just got to wait for the place selling the cutter to open up on Tuesday, and order some acetal to make my own gear.

[Rocboni]

Hi
Id just like to say that my lathe is functional again, thanks to petes gear cutting skills, he made a very professionally job of cutting the gear.
thanks

[Andy B]

Great news!
What material did you use in the end?
Might be interesting for others if you can keep an eye on how much (if any) wear you get and report back.

Andy

[Pete.]

I made the gear from Delrin Acetal, since that was the material specified as suitable in the quote I got from the gear company. It's a material that's commonly used for gears.

It was very satisfying to get a PM from Rocboni saying it fitted and ran well, since I had never cut a gear before this. I actually made a mistake indexing the very first one and ended up with a single under-sized tooth, so I bought some thicker material and made a pair as one then parted them to give one for me and one for Rocboni. Hopefully they will last another 25 years or more