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-   -   looking for flexible shaft coupler for 1/2 inch hex (http://www.chiefdelphi.com/forums/showthread.php?t=153968)

Bruceb 20-01-2017 13:03

looking for flexible shaft coupler for 1/2 inch hex
 
Do any of you know where a person could get a flexible shaft coupler for high rpm and 1/2 inch hex shaft?
Or how one would make them without a CNC mill?

Oblarg 20-01-2017 13:05

Re: looking for flexible shaft coupler for 1/2 inch hex
 
How much load does the coupler need to take? Is this an encoder coupling (i.e., basically no load) or are you looking to actually transfer motion within a mechanism?

If it's the former, your best bet is to turn the shaft down to 1/4'' round and use an ordinary helical beam coupling.

If the latter, you could possibly hex broach a spider coupling.

RoboChair 20-01-2017 13:07

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by Oblarg (Post 1633978)
If the latter, you could possibly hex broach a spider coupling.

Why not use the surgical tubing coupler method?

Oblarg 20-01-2017 13:10

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by RoboChair (Post 1633980)
Why not use the surgical tubing coupler method?

We used to do this, but found last year that this is prone to introducing a fair bit of noise into the encoder readings. We never quite found out why, though my best guess is some sort of stick-slip effect.

It's not horrible if you use thick tubing and align the shafts well (it gets much, much worse with increasing axial misalignment), but the beam couplers have no such effect and are free from FIRST Choice so we use those now.

cbale2000 20-01-2017 13:11

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by Bruceb (Post 1633975)
Do any of you know where a person could get a flexible shaft coupler for high rpm and 1/2 inch hex shaft?
Or how one would make them without a CNC mill?

How flexible are we talking here? What kind of torque are you trying to transmit?

Cothron Theiss 20-01-2017 13:27

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Your chances of finding hex bore flexible shaft couplers are practically zero. But if you can round off the end of your hex shafts to 1/2" or a slightly smaller diameter, you can find flexible couplings.

Bruceb 20-01-2017 14:17

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by cbale2000 (Post 1633986)
How flexible are we talking here? What kind of torque are you trying to transmit?

RS-775 pro direct driving 2 inch AM wheel for shooter through a VP planetary 1-1.

Jon Stratis 20-01-2017 14:25

Re: looking for flexible shaft coupler for 1/2 inch hex
 
trying to drive a shooter, I wouldn't rely on a flexible coupler - a failure of that part would be pretty rough. I'd drive it through belts or gears instead.

Oblarg 20-01-2017 14:26

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by Bruceb (Post 1634033)
RS-775 pro direct driving 2 inch AM wheel for shooter through a VP planetary 1-1.

I'd use a spider coupling for that. You can hex broach one, or else turn down the end of your shaft.

cbale2000 20-01-2017 14:48

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by Bruceb (Post 1634033)
RS-775 pro direct driving 2 inch AM wheel for shooter through a VP planetary 1-1.

Why not just use a non-flexible coupler? Why does it need to flex?
The average flexible coupler is not really intended for these kinds of load transmissions. You might be able to get away with a universal joint but even that I wouldn't recommend for long term use because of durability and efficiency loss.

dradel 20-01-2017 15:02

Re: looking for flexible shaft coupler for 1/2 inch hex
 
A 775 spinning at full boogie is up around 18,000 rpm ! A flex joint may not like the rpm if things aren't ballenced.

Bruceb 20-01-2017 15:39

Re: looking for flexible shaft coupler for 1/2 inch hex
 
I have a non flex coupler on there now it it vibrates a lot. That is why I was looking for a flex coupler of some kind. Maybe I will just cushion mount the VP and motor.
Will that vibration have an effect on the encoder?

Cothron Theiss 20-01-2017 15:43

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by Bruceb (Post 1634093)
I have a non flex coupler on there now it it vibrates a lot. That is why I was looking for a flex coupler of some kind. Maybe I will just cushion mount the VP and motor.
Will that vibration have an effect on the encoder?

If vibration is your concern, a flexible coupler won't fix it. That's a product of the system design as a whole. You need to make sure everything is aligned properly, nothing's too out of balance, and all your motion is smooth and steady.

yarden.saa 20-01-2017 15:50

Re: looking for flexible shaft coupler for 1/2 inch hex
 
We had last year 775Pro on VP gearbox 3:1 direct drive a hex shaft with vex hex shaft coupler with no problem of vibrations. You are probably going too fast, I don't think you need 18000 rpm for a shooter.

cbale2000 20-01-2017 16:09

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by Bruceb (Post 1634093)
I have a non flex coupler on there now it it vibrates a lot. That is why I was looking for a flex coupler of some kind. Maybe I will just cushion mount the VP and motor.
Will that vibration have an effect on the encoder?

If you're using a versa-planetary anyways, why not just use a versaplanetary encoder?

Bruceb 20-01-2017 16:57

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by yarden.saa (Post 1634102)
We had last year 775Pro on VP gearbox 3:1 direct drive a hex shaft with vex hex shaft coupler with no problem of vibrations. You are probably going too fast, I don't think you need 18000 rpm for a shooter.

no probably not all that but we are spinning a 2 inch wheel

Bruceb 20-01-2017 16:58

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by cbale2000 (Post 1634114)
If you're using a versa-planetary anyways, why not just use a versaplanetary encoder?

because the encoder made for the RS-775 pro is much smaller and I have heard good things about it.

Cothron Theiss 20-01-2017 17:12

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Ok, so I think there are a few things you should look at to try and fix the problems in the design rather than patch over them. You should have some reduction coming off of an RS-775. You already have the VersaPlanetary in there, why not change it to an actual reduction? This will vastly improve the accuracy and consistency of your shot anyways. As for the encoder, if you already have the encoder set up for the RS-775, that's fine. But you can also use the VersaPlanetary integrated encoder. It works very well also.

cbale2000 20-01-2017 18:28

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by Bruceb (Post 1634136)
because the encoder made for the RS-775 pro is much smaller and I have heard good things about it.

What motor and encoder specifically are you trying to use? Perhaps provide links?

To my knowledge there is no such motor as an "RS-775 Pro"; there is an "RS-775" and a "775 Pro" but these are very different things.

Tom469 20-01-2017 20:39

Re: looking for flexible shaft coupler for 1/2 inch hex
 
For a rotary encoder, I suggest you turn the end of the Hex shaft down to ~ 1/4" and use a piece of 1/4" fuel hose, ~ 1 1/4" in length and use a couple of flat spring clamps to clamp the ends. Then carefully align it. The fuel hose and flat clamps are standard lawnmower items.

The harder mechanical flex couplers transmit a lot of vibration to the encoder, and can cause pre-mature failure. The company, that I worked for introduced a flex coupler then discontinued their use. And, went back to the fuel hose.

PAR_WIG1350 20-01-2017 22:42

Re: looking for flexible shaft coupler for 1/2 inch hex
 
Quote:

Originally Posted by cbale2000 (Post 1634179)
<snip>To my knowledge there is no such motor as an "RS-775 Pro"; there is an "RS-775" and a "775 Pro" but these are very different things.

The designation RS-775 is borrowed from Mabuchi Motor Co., Ltd. and it indicates a round, carbon brushed DC motor with a 5-pole, size 7 armature (diameter) and a size 7 housing (length). There are at least four legal motors that satisfy that description:
  • AndyMark's RS775-5
  • AndyMark's RS775-125
  • BaneBots' RS-775 18V
  • WestCoast Products' 775pro

The first two are almost identical. The latter two are much more powerful than the former, but distinct from each other. Any one of them could be called an RS-775 with roughly the same degree of accuracy. It is prudent to clarify, but I believe that the motor in question is a 775pro.


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