Need help: replacement disc for Thermoid dampener shaft couplings

I am doing some work at Hanford Mills Museum during the winter when the Mill is closed. One of the items which is overdue for repair are two (2) shaft couplings on some of the lineshafting. These couplings are "Thermoid" flexible dampener couplings. These couplings use a disc of rubber/canvas with holes for the coupling bolts and bushings.

The material is a multi-layered composite of rubber and canvas, about 1" thick. This material was cut or molded into discs, with six bolt holes- 3 bolts in each coupling hub flange. Steel bushings with fit in these holes. If the bolt circle is not precise, misalignment or worse can result.

I have this same type Thermoid coupling on my old Worthington air compressor, which is direct coupled to its motor. Years ago, I tried to contact Thermoid about a replacement element for this coupling and could not find either Thermoid or a successor. Searches on the internet have not turned up anyone making similar couplings.

The closest to this style of coupling which I had seen was used by Ford on some of their Explorer driveshafts instead of conventional U joints, and this style coupling was also used on some auto steering shafts.

Hanford Mills, being a preserved/working museum, wants to stick with the original couplings, so putting in a more modern coupling is not an option. These couplings may have been put in during the 20's or 30's.

My thoughts as to obtaining a replacement disc for these couplings is to "reverse engineer" and make them. I can have material CNC waterjet cut quite precisely, which I had done to duplicate some heavy synthetic rubber parts when I was working at the powerplant. Finding the rubber/canvas material in 1" thickness is the issue.
An alternative might be to use polyurethane, but I am at a loss as to the proper specfication for polyurethane with approximately equivalent properties to the canvas/rubber.

I would appreciate hearing from any members who can help me with either the source for new canvas/rubber, or polyurethane and the spec/source where we can buy some.

I've been holding my breath with my old Worthington compressor. The dampener element is kind of "petrified" with age (dating to 1947 or thereabouts). The couplings at the Mill are pretty well shot, with the elements even more petrified and cracking and coupling bolt holes wallowed out. Any help will be appreciated, for sure.

Thanks !
Joe Michaels

Common on old cars

My '28 Nash Advanced Six had at least one between transmission and rear end - instead of the usual U-joint

Since both driving and driven elements clamp these discs it would seem laminated from multiple thicknesses would be functional

Joe ,
I the material you are describing sounds a bit like some old conveyor belting I have here that I used for floor mats at one time.
The material I have is old and rotten now and only about 1/2” thick .
Maybe you will get some ideas where you could find a piece here.
Conveyor Belting - Google Search
Some where there is a mine , quarry or crusher local to you might have an end cut of something thick enough or perhaps you could glue or stich a couple of thicknesses together.
Regards,
Jim

Use a steel disk or gear coupling both have been around since the 30’s...

Joe - What diameter do the discs need to be? Would you be willing to layer two 1/2 thick pcs to get the full thickness? If so, I think I have some 1/2" thk x 6 inch wide rubber canvas material and I would donate enough for this project if you don't need more than 6 inch diameter. If interested I can take a fresh look to see what I really have if I can get to it given that all the rusty stuff is shoe-horned in for the winter.

Try here, Joe:
http://www.gmspolymer.co.uk/flexible-couplings.htm

Can you post a picture or a catalog ?

digger doug said:

Can you post a picture or a catalog ?

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Me? Read the link, made to order from original drawings.

I, too, would use two layers of 1/2" conveyor belt, directions crossed...glued together if necesaary but probably not. I think I have some, happy to send you as much as you need for the RR and your own compressor, if you can't find it nearer at a quarry or cement plant. Or four layers of 1/4" belt from a round hay-baler....eight from a supermarket checkout line belt...

I've made lots of mounts and dampers from tire sidewalls, but not easy to get a big enough flat piece for your application.

I believe the term for couplings like this, is a "rag joint."

tdmidget said:

Me? Read the link, made to order from original drawings.

Click to expand...

I read the OP.

Don't lecture me.

I’d say to stay away from urethane rubbers, they’re good for a while but eventually they break down and become an icky gooey mess, belting seems like the best bet but 1” thick may be tough to find, if it were me I’d glue some sbr rubber belting together in layers and make the part from that, or get some rubber sheet of that thickness. I dealt with a similar joint once on an old vacuum pump, “rag joint” is what they’re called.

Thank you to all who've contributed and provided answers to my query. I am going to get some conveyor belting material and glue it together to form 1" thick material.

The remaining question is what to use for adhesive ? At the powerplant, we used this product called "Barge Cement", which was what leather workers and shoe makers use. We used it to glue together rubber or neoprene seals and gasketing, or to stick them onto steel surfaces until assembly of mating parts could be made. Barge Cement is basically a "contact" type of adhesive. What is has in the way of shear strength is something unknown. It is the only adhesive for this kind of work I've had any experience with. We did use a Devcon product on field splices on some timing belts (which were structurally pinned together, but the Devcon kept things from flapping and coming apart). The Devcon product was a urethane compound, which is what the belts were made of. It seemed to set and remain flexible and bonded well to the belting. We ran those belts on governor drives on smaller hydro turbines 24/7 for months on end, and years went by before we had to replace any of those belts. I wonder if using something like the Devcon product- more of a semi fluid goo and not at all like the Barge Cement- might be a better choice ? Laminating the conveyor material by sandwiching the plies of belting with adhesive between two steel plates in a shop press is what my gut is telling me, holding the material in the press for maybe 24 hours until the bonding agent (whether Devcon or Barge Cement) is fully set. This should eliminate any blisters or bubbles between the layers of belting material.

For the discs in the shaft couplings, my thinking is to try to create a "one piece" disc by laminating several thicknesses of conveyor belting together. Once I have the material laminated together, the next step would be to send it to the CNC waterjet cutting shop with a drawing. This should result in discs with very precise dimensions, including coupling bolt holes.

I cannot duplicate the exact design of the original Thermoid discs, as the bushings for the coupling bolts are apparently vulcanized into the discs. Instead, I will have the bolt holes cut a bit undersized (perhaps 0.005" ?), and machine new bushings with a generous chamfer on the ends. These will rely on a press-fit into the disc.

A few years back, when this whole issue first came up at Hanford Mills, I had the idea of using an automotive dampener coupling of this type. Car makers still use this type of flex coupling in drivelines, and replacements are not expensive. I had figured I'd get some steel and make new flanged coupling halves with bolt circles and overall dimensions based on the automotive flex coupling discs. This was shot down as "not authentic" or something like it. Since the old couplings hadn't failed, the matter was shelved. Now that we are into a winter and planning on catching up on overdue repairs, this coupling issue is back on the front burners.

As I said, about the only issue still confronting me is the choice of adhesive. Thanks again for the suggestions and help.

Barge "All-Purpose Original" (neoprene base) may be a very good bet.

But I am not sure about any adhesive or system aside from "vulcanizing" into one piece. Seems as if the torque would tend to pop the layers apart. I doubt that two layers un-connected would work the same as one solid piece, but it would depend on the coupling assembly, and how well it constrains layers, if at all..

"Barge cement" is not one product anymore.

Barge Products - Barge Cement

digger doug said:

I read the OP.

Don't lecture me.

Click to expand...

Kind of delicate , aren't you? The site appears to be a labor of love, like Tony's lathe site. If they make them one at a time you expect a catalog? You're lucky they don't expect you to crawl on your knees for them and you want a catalog for one offs?

You might sandblast the OD on the bushings or just rough them up real good and have them perfectly degreased then glue them in, another possibility would be to make them fairly thin and form the ends over like grommets this will give you a mechanical bond of your layers on top of the glue. Not sure on the glue though, I’d look in to wherever is intended to be used used for the purpose of joining the ends of that belting, I’ve seen glued joints on rubber belt that have lasted a very long time, never had to glue one my self though.

How about....Disc coupling... Gujarat Rubber Industries,..Ahmedabad,Gujarat. Cost...about $5.00 each depending on size....These are the type i am familiar with,had stacks of them all sizes in the maintenance shop,every motor,reduction box,drive shaft was joined by a disc coupling .They are actually fairly hard,but flexible.Steel reinforcing plates around the holes,but no steel bushes which would load up with red dust,and rust solid.

Similar though usually molder rubber couplings for marine prop shaft use.

To remake the original two layers of belting sounds like a good plan to me.
I bet they'd be fine without any glue, but wouldn't hurt to use Barge cement, which I also think is a good choice.

Talk to the water jet cutter before you get to far along.They may prefer to cut them at 1/2" thick and then assemble if there is any trouble holding tolerance on the bottom side of a 1" cut.

Rag joint is what they call the rubber canvas used on steering shafts. Gwebo is what they call the rubber dounut / U-joint in euro drive shafts like Alfa's

44dwarf said:

Rag joint is what they call the rubber canvas used on steering shafts. Gwebo is what they call the rubber dounut / U-joint in euro drive shafts like Alfa's

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Guibo. I’ve replaced many on older Merc and Bimmer drivelines. Photo from Google.