Flexible shaft couplers - specs

For flexible shaft couplers such as AdaFruit 1175, Digikey PN 1528-1286-ND:

  1. Are there RPM limits more or less inherent to that sort of product? I need to spin it at up to 8k RPM, albeit at low torque.
  2. They appear to be mostly designed to absorb vibration in the z-axis (longitudinal). How much angle displacement (bend) can they tolerate at speed? 1 degree? 2 degrees?


In response to your questions:

  1. Yes, but exactly what it is for any given product or what the actual limiting factor is in any given case, those aren’t easy questions to answer. If nothing else, rotational imbalances will start getting problematic at some point. I’ve seen a number of similar products rated for 6-10K, but that doesn’t mean this one would tolerate the same

  2. Similar products can be found rated to take up sub-mm translation along the shaft axis, and perhaps 2 to 5° of angular misalignment. Again those are similar products, but not this one.

If designing something for commercial production, I strongly suggest using suppliers that publish thorough specifications for the products on offer; dimensions with tolerances, torque and alignment tolerances, inertial moments, etc. One can’t expect things that aren’t specified to be consistent from one example to another, or characterized/guaranteed in any respect. If one’s only buying an item once for personal amusement, quality control usually isn’t a huge issue. Different story if one’s buying 10K of something over a year or two to build a product for which one bears liability of warranty…

Hello scarter,

Unfortunately this product currently doesn’t have the testing of which you are looking for.
Since it is aluminum, If it were to generate heat, it would also dissipate of it rather quickly -if not on its’ own, through the shafts mounted on.

The other part of the variable is the time you intend to run at these speeds, but again unfortunately I don’t see further documentation.
As a side note if you are forced to run one of these and they do build up excess heat, a fan or a liquid cooling dripper of some kind may go a long way.

Thanks, Rick. Yeah, I tried to find similar parts with more precise values (e.g. from McMaster Carr) but they don’t seem to have anything of similar range (e.g. nothing for 3mm shaft, only rather larger).

Thanks, Ryan!

I hadn’t thought about dispersive heating in the elastomeric element, but that makes sense. In my configuration it will be easy enough to arrange cooling air.

I like McMaster as much as the next guy (maybe more) but a specialist shop they 'aint. SDP-SI is my next stop for mechanicals of this sort when the occasion calls for something more exotic. Perhaps these listings would hold something useful.

You are the man, at least for this sort of thing. I’d never even heard of SDP-SI, but now I know.

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