Shaft coupling

[Dauph]

Hi all,
I'm attempting to build a drum sander using an old drill. I attached the drill to the drum shaft using an aluminium flexible coupler. It snapped on the first test with barely any load on it.
It was cheap, and did mention 3D printers as a use, so I guess it wasn't up for the speed/torque of my plan.
I found this on Amazon https://shorturl.at/am5Wf It has no reviews but is potentially a better design that what's mostly available on Amazon
I found one that is described as "high torque" but, again, no reviews, and pricey.
Any thoughts/suggestion?
Edit: Photo is of the test set up and broken coupler

 

[ChaiLatte]

Take a photo of your setup showing the failed coupler in place.

You provide insufficient concrete information in your post to make any suggestion any better than consulting tea leaves.

 

[Dauph]

Take a photo of your setup showing the failed coupler in place.

You provide insufficient concrete information in your post to make any suggestion any better than consulting tea leaves.

Done. Please see above. Ta!

 

[Amplidyne]

Try amazon and search "Small Universal joint" Sourcing map have 10 and 12mm joints on there. Should be stronger than the spring type I would think.

 

[Phill05]

I don't think you need a coupler for that direct in the chuck as you show should be fine.

 

[ChaiLatte]

I don't think you need a coupler for that direct in the chuck as you show should be fine.

You are right. The small difficulty is that in the photo the drill is free-floating.

However, as it is a corded item, the collar on it will be a standard 42mm or 43mm (cannot remember which of the two is correct). Making a clamp that restrains the drill and is concentric with the shaft will eliminate the need for a coupler.

Make your best efforts with it, and if it is not quite right when tested, you can sand its base down to lower it or shim it up with paper if too low.

So long as the drill is clamped in place, a real cheapskate option to take out any residual misalignment is a piece of rubber hose joining the drum shaft to a short stub shaft held in the drill chuck. Minimal gap between the two shaft ends. It might act as a safety clutch when your tie gets sucked into the drum.

 

[Dauph]

You are right. The small difficulty is that in the photo the drill is free-floating.

However, as it is a corded item, the collar on it will be a standard 42mm or 43mm (cannot remember which of the two is correct). Making a clamp that restrains the drill and is concentric with the shaft will eliminate the need for a coupler.

Make your best efforts with it, and if it is not quite right when tested, you can sand its base down to lower it or shim it up with paper if too low.

So long as the drill is clamped in place, a real cheapskate option to take out any residual misalignment is a piece of rubber hose joining the drum shaft to a short stub shaft held in the drill chuck. Minimal gap between the two shaft ends. It might act as a safety clutch when your tie gets sucked into the drum.

It was a test set up so I know the drill not being clamped was less than ideal. I did have an F clamp on while it ran. The coupler failed when I tried sanding the drum lightly, so it seems more load related that it failed. I now realise I may have had the coupler the wrong way round, so it was trying to uncoil. Can't have helped! I'd like something a bit more substantial than a bit of tube but, I'll bear it in mind. Ta

 

[Dauph]

Try amazon and search "Small Universal joint" Sourcing map have 10 and 12mm joints on there. Should be stronger than the spring type I would think.

They look much more sturdy. I assume it'll do the same job I.E. make allowances for slight misalignment/deviation and vibration?

 

[ChaiLatte]

...make allowances for slight misalignment/deviation and vibration?

A single universal joint will only allow angular misalignment in one plane.

In addition, in anything but a coaxial arrangement, a single UJ is not constant velocity, so the drum speed will vary throughout one revolution.

It would give you more options with a pair of joints, correctly phased.

 

[Sachakins]

With accurate alignment there's no need for a coupler.

 

[Dauph]

With accurate alignment there's no need for a coupler.

I guess I'm about to find out how accurate I can be

 

[Richard_C]

If you are still struggling after your next trial you could think about a change in design. Put a pulley on the drum shaft, put a pulley in the drill bit, mount the drill so the pulleys line up and connect with a rubber belt. Think old fashioned Meccano parts as design inspiration.

 

[ian8555]

This style is a really good cost/performance option that I use a lot in CNC building. Sometimes called Oldham style.👍

 

[Dauph]

This style is a really good cost/performance option that I use a lot in CNC building. Sometimes called Oldham style.👍

View attachment 190234

I did see those but had no idea how they work. What is backlash in this situation/application? Might give it a go. Cheers

 

[Dabop]

Backlash is important in CNC applications- where reversing direction with some backlash means that you have misalignment between passes in opposite direction...
eg in the forward direction, you have an action take place at say 5mm, 10mm, 15mm, 20mm etc- but with a coupler with say 1mm backlash, instead of the reverse direction happening at 20,15,10,5, it happens at 21,16,11 and 6 (the extra 1mm comes from the 1mm backlash in this example)
Obviously this would be bad for say a 3d printer, laser or cnc milling machine... with rather poor results...
🤬

In your application, it wouldn't be of any concern however... strength is more important than backlash in this case...
(you can get spiders in a large range of different sizes up to some truly massive ones...)

Applications include power transmission to industrial equipment such as pumps, gear boxes, compressors, blowers, mixers, and conveyors. Lovejoy’s Jaw Type couplings are available in 24 sizes from a minimum torque rating of 3.5 in–lbs (0.4 Nm) to a maximum torque rating of 170,004 in–lbs (19209 Nm) and a bore range of .125 inches (4.45mm) to 7 inches (178mm). Lovejoy’s standard bore program covers AGMA, SAE, and DIN bore/keyway and spline bore combinations.

Can you imagine the force one with a 7" motor shaft would take to break...
🤯

 

[okeydokey]

If you are still struggling after your next trial you could think about a change in design. Put a pulley on the drum shaft, put a pulley in the drill bit, mount the drill so the pulleys line up and connect with a rubber belt. Think old fashioned Meccano parts as design inspiration.

Thats the way I would tackle it as well - btw anyway of getting rid of the drill and using a small motor with variable speed as I think the noise of the drill going full bore would drive me bonkers (more than usual). I suspect a sewing machine motor with foot pedals would not be strong enough.

 

[stuart little]

I suggest 2 sprockets & a toothed belt.

 

[Stevekane]

Whats wrong with a piece of reinforced rubber hose, aka heater hose,,isnt that what was always used in these situations?
Steve.

 

[Fergie 307]

Problem with a lot of couplings is that they are intended for quite low rpm, as such they are not balanced. In your application they may well run out of balance and shake it to bits!
I would mount everything properly with no coupler initially. If that doesn't work out, or to get it more compact, use pulleys and a belt. Also allows you to vary the relative speed of the drum and motor.