[SSfab]

Just wondering if you absolutley need those $16-$20 motor couplers? I seen on hoss's site, it appears he just made his own. Do i NEED them?

[Oldmanandhistoy]

Hi,

Would depend on your application but could be cheaper than having to replace stepper motors due to damaged bearings or shaft.

Do a search for more info here on the zone for more details

John

[escott76]

They make up for errors in alignment while allowing the motor to spin without excessive friction. Unless you can be sure that :
a) motor and driven shaft are perfectly parallel.
b) motor and shaft are aligned about the center
c) whatever you use to couple fits both shafts without slop and it's bores are aligned as above
you will really want to use a coupler.
Or you could waste a bunch of time "making your own", having problems which you can't be sure might be the fault of the couplers, or might be something else. Sometimes $20 (or $60 for three of em) is cheap compared to the headache and frustration they save.

[SCzEngrgGroup]

Just wondering if you absolutley need those $16-$20 motor couplers? I seen on hoss's site, it appears he just made his own. Do i NEED them?

If you're going to direct-couple the motors to any other shaft, you NEED them. If you don't, and you don't get the shafts PERFECTLY aligned, you will eventually break one shaft or the other.

You can make your own Old-style couplings very easily, using aluminum round stock, and a slab of 1/2" UHMW. Just mill a 1/4" wide by 1/4" deep slot on each side of the UHMW, with the slots 90 degrees to each other, then mill the round stock with a single 1/4" wide by 1/4" high "rib" across one face. Make the rib a snug sliding fit in the slots in the UHMW. Drill the round stock down the middle for the shafts, and drill and tap for a set screw. I made a set years ago, and they were zero backlash, and worked flawlessly. Making them larger diameter (mine were 1-1/2") makes the dimension less fussy.

Regards,
Ray L.

[hoss2006]

Well, it's been nearly 3 years with the solid couplers and no damaged bearings or broken shafts
Simple to make, dirt cheap and zero backlash.
I wasn't worried about my skills to make sure everything was parallel but the
hobbyist might want to go with the flexible couplers instead.
One of the reasons I give a link on my website.
Keling sells a couple of nice looking coupler types.
Hoss

[SSfab]

Enough said. I will purchase some. I was unaware of the reasons for using them.

Good info as usual.

Thanks, Scott

[SCzEngrgGroup]

Well, it's been nearly 3 years with the solid couplers and no damaged bearings or broken shafts
Simple to make, dirt cheap and zero backlash.
I wasn't worried about my skills to make sure everything was parallel but the
hobbyist might want to go with the flexible couplers instead.
One of the reasons I give a link on my website.
Keling sells a couple of nice looking coupler types.
Hoss

Hoss,

Three years? That's just about how long mine lasted before the first motor shaft snapped. You may have just jinxed yourself! :-)
Solid couplings will work, *if* everything is lined up really well. But that is hard to achieve (and even harder to prove you've achieved it), and the couplings I described are cheap and easy to make. Cheap insurance, if you ask me.

Regards,
Ray L.

[steve323]

A cheaper alternative is the Lovejoy connectors from Enco at about $8 for 2 hubs and a spider. This option also allows you to easily join 1/4" stepper motor shafts with 3/8" or 1/2" screws.

Steve

[Crevice Reamer]

A cheaper alternative is the Lovejoy connectors from Enco at about $8 for 2 hubs and a spider. This option also allows you to easily join 1/4" stepper motor shafts with 3/8" or 1/2" screws.

Steve

But Lovejoy types may not start out Zero backlash, and will add backlash as the spiders wear. Helical couplings are the best of both worlds: Solid, so zero backlash, and yet flexible. Flexible couplings still need to be REASONABLY close to alignment though.

CR.

[SSfab]

I don't like the whole nylon/plastic spider idea, simply because it will wear, thus become a headache.

[SCzEngrgGroup]

I don't like the whole nylon/plastic spider idea, simply because it will wear, thus become a headache.

Obviously you've never tried it. I used mine for years, and they are backlash-free to this day. It's a tight sliding fit, using essentially self-lubricating plastic on a smoth aluminum surface. There is no measurable wear. And they will tolerate significant misalignment with near zero stress on the shafts.

Regards,
Ray L.

[Al_The_Man]

One of the oldest and most efficient (zero backlash) is the Oldham coupling http://www.mechanisms101.com/oldham.shtml
They start at about $8 in the Misumi catalogue.
I have found that applications that use aluminum Helical with in any kind of medium/high torque servo, they usually end up fracturing due to metal fatigue, and end up putting on a Stainless version.
Al.

[LongRat]

One of the oldest and most efficient (zero backlash) is the Oldham coupling http://www.mechanisms101.com/oldham.shtml
They start at about $8 in the Misumi catalogue.
I have found that applications that use aluminum Helical with in any kind of medium/high torque servo, they usually end up fracturing due to metal fatigue, and end up putting on a Stainless version.
Al.

--Agreed, I have been running oldham couplers on my mill since I converted it. I have thousands and thousands of hours on it, and still zero backlash. Definitely recommended. I run a solid coupler on my z, and that works too. It's a 1/2" shaft... can't see it snapping.

[hoss2006]

Hoss,

Three years? That's just about how long mine lasted before the first motor shaft snapped. You may have just jinxed yourself! :-)
Solid couplings will work, *if* everything is lined up really well. But that is hard to achieve (and even harder to prove you've achieved it), and the couplings I described are cheap and easy to make. Cheap insurance, if you ask me.

Regards,
Ray L.

3 years and no problems is all the proof I need, the original motors are still in use.
I built my conversion for myself but have had to add other options like the link to "flexible" couplers for all the folks that want something easier.
I'll add a couple new ones from the great tips posted here.
Hoss

[Arquibaldo]

I´ve beens thinking about this problem, and I find HimyKabibble's
recipe for a homemade coupler (post #4) is great - I´m going to
try it.

However, if you are really going to spend around 20 bucks for a coupler,
I always thought that I might opt for 2 pulleys+timing belt instead.
Don't you think this would be a better solution, and probably cheaper too?
With a timing belt you also have another great advantage: you
are free to choose a better position for the motors, avoiding "stiking"
motors, ending up with stiffer motor mounts and a more compact
machine.

Am I overlooking some disadvanges?

Nelson

[fretsman]

Does anyone know where to get these couplers?

I saw them on ebay but they seem awefully salty in price....

Thanks,
Dave

[SCzEngrgGroup]

I´ve beens thinking about this problem, and I find HimyKabibble's
recipe for a homemade coupler (post #4) is great - I´m going to
try it.

However, if you are really going to spend around 20 bucks for a coupler,
I always thought that I might opt for 2 pulleys+timing belt instead.
Don't you think this would be a better solution, and probably cheaper too?
With a timing belt you also have another great advantage: you
are free to choose a better position for the motors, avoiding "stiking"
motors, ending up with stiffer motor mounts and a more compact
machine.

Am I overlooking some disadvanges?

Nelson

Only cost, and potentially a small amount of backlash, depending on what type of belt you use, how well the pulleys fit, and how you mount and assemble it all. You'll have two pulleys, and a belt, which will cost a lot more than a coupling, especially a home-made one. Then there's the extra bracketry, and more complex machining, since it needs to eb adjustable to tension the belt properly.

Regards,
Ray L.

[Riceburner98]

Helical with in any kind of medium/high torque servo, they usually end up fracturing due to metal fatigue, and end up putting on a Stainless version.
Al.

One of the guys at work here was building a high-speed turntable for product testing, he hit a particular RPM and the aluminum helical coupler he was using hit some resonant frequency and exploded into half-moon shaped shrapnel. Think it was a few thousand RPM, with a large plexiglass platter for the table. Replaced it with a stainless one and all was OK.
As far as "perfectly" aligning a motor with a direct coupling, as long as there's a little float in your motor mount holes, once you clamp down the coupler on the motor and 'screw shaft the motor is automatically aligned as well as it can be, then when you tighten the bolts on the motor it keeps it there. (assuming you don't let the motor "free hang" on the screw after you clamp the coupler down and before the mount bolts are tightened) I don't see any problems with it.. I use stainless flexible couplers only because they already came with my 'screws.. <- edit: this assumes, of course, that your motor mount surface is perfectly perpendicular / square to your screw. if not, then it's going to tweak the shaft of both of them as you tighten down the motor mount bolts...

[project5k]

ok, i've been using the lovejoys for lots of years in different projects, some are high rpm and some are high torque, and neither have given me any issues, or show any signs of wear.. and besides, even if you were able to wear out the spider... youd notice it long before it completely went away, and you can order new ones for cheap, in different materials even. i've tried, and on my cnc machine, i cant measure any backlash on my lovejoys...

further more, if your really that worried about them wearing out, once you have these in, you could allways use the machine to make more spiders, or whatever, but i doubt you'll ever really need them unless something goes very wrong, in which case, your couplers will be the last of your worries.

silly question, oldham coupler? is that like what we used to call a rag joint? like what used to be right above the steering box on cars before rack and pinion?

[Al_The_Man]

.

silly question, oldham coupler? is that like what we used to call a rag joint? like what used to be right above the steering box on cars before rack and pinion?

Not really, the Rag joint was usually a disc of fibre impregnated rubber or similar, and each half of the coupling was bolted firmly to it each half 90deg to each other.
There were slight variations.
The link I showed has the Oldham principle.
BTW Lovejoy is a Manufacturer and of many various types, not just one.
Al.