coupling calc 1

[kpl012]

I have shafts both threaded on the ends, piston and actuator, connected by a screwed on coupling bolted together with a shim in the middle. This is for ease of installation and removal. The loads are along the shafts. What is a good calc to use for proper bolt size, coupling mat'l, coupling thickness and bolt pattern?

 

[desertfox]

Please post a sketch and show where the loads are acting.

 

[kpl012]

loads go one way when piston downs down then the other way when piston goes up.

 

[desertfox]

Thanks for the sketch, on the piston side it appears you have a retention washer is that correct? also on the actuator side there appears to be nothing to stop the actuator from unscrewing itself from the coupling or is there something I cannot see.
If the coupling moves with the two rods back and forth I can't see how any load is transferred to the coupling other than vibration or shock, again can you give all the information on this you have rather than spread it over several posts.

regards

desertfox

 

[kpl012]

Sorry. Yes you are correct. On the actuator side behind the thick shim there is a retainer washer, has a tab that fits in the key way on the shaft. The two couplings are held together with the fasters, SHCS's.

 

[desertfox]

How fast is this rod travelling will there by any tendency for the actuator side to try and separate from the piston side during operation (caused by acceleration) until we know the loads and speed its very hard to help you.
Please give us all the information on this you have, otherwise we will have 20 further posts trying to get information to help you.

 

[kpl012]

Sorry. The rod will travel 22 inches in 30 sec. The max pressure in the cylinder where the piston is will be 7500 psi. It is controlled by hydraulics with a relief set for 7500 psi. Won't be any acceleration.

 

[CoryPad]

Calculations can be done according to VDI 2230.

 

[desertfox]

So on the annulus side of the cylinder what is the force, once you have that force you can start doing the calculations as suggested by Corypad

 

[dvd]

My immediate thought when I saw the sketch was that you need an alignment coupling. If the cylinder rod is guiding the load (or if the load is guided and not perfectly aligned with the cylinder) there may be high loads on the rod seal along with high induced loads throughout. You might consider using something like one of these:

http://www.trdmfg.com/pdf/TRD ALIGNMENT COUPLERS.pdf

Call and talk to an applications engineer for specifics if you are uncertain how to apply.

 

[tbuelna]

Based on the sketch provided, it looks like it will be a bit complicated to get everything aligned and preloaded properly. For example, there is a defined indexing between the two halves of the coupling based on the number of bolts used. And the shim installed between the mating rod end faces and coupling faces must have the precise thickness needed to produce exact alignment of the bolt holes in the mating coupling flanges. If the fit between all of these components is not precise, then it will be difficult to determine exactly how loads are transferred across this connection. I don't see how it would be possible to have the shim thickness precisely match both the gaps between the rod ends and the coupling ends while also providing the correct indexing for the coupling bolt holes.

 

[Tmoose]

MS word newer than 2000 is needed to view *.docx files. Seems like there are a few folks still running older versions of Word, Autocad, etc, and haven't downloaded a free viewer yet.

I save files in older formats, or a neutral format like PDF. As late as 2002 a major US automotive "transfer line" manufacturer required that our spindle drawings be submitted in ACAD 14.

During saving It's usually just 2 extra mouseclicks to activate a pulldown menu and select a version from 1 score years ago. Sometimes some interesting and unexpected save options are available too.