1. Home
  2. ⚙ Model Engineering in the UK
  3. Could somebody make a D-shaped shaft for me? (for payment of course)

Could somebody make a D-shaped shaft for me? (for payment of course)

Hi all,

I was pointed to this group from uk.d-i-y as I am hoping some kind and able soul out there with a lathe and/or milling machine might be able to help me out here....

At the risk of sounding like I've got too much spare time on my hands I am in the middle of project building a network-enabled cat feeder. The current design is based around a cereal dispenser driven by a high-torque/ low-revs motor, the latter being controlled by a modified Cisco switch.

The following diagram shows roughly what I am doing from a mechanical perspective:

formatting link
The cereal dispenser contains a rubber flapper mechanism which accommodates a plastic 'D-shaped' shaft connected to a knob. Whilst I have managed to separate the shaft from the knob and connected everything up I am concerned that over time the high torque required when food gets caught in the flapper will cause the connection to the brass coupling to fail. This is based on the fact that the plastic shaft is rather soft and is not held all that firmly by the grub screw in the coupling. I have considered inserting a metal shim of some sort but I really can't see it lasting.

Hence, I am wanting to replace the plastic shaft with something made out of metal. Unfortunately whilst my apprenticeship days taught me the skills to do this I do not have access to the necessary machines to do so.

Would anybody be able to help me out here? That kind person would be suitably compensated as required. I have made a drawing showing the necessary dimensions (using Word - my teachers would not have been impressed!):

formatting link
As you can see, the coupling to the motor (right-hand side) is required to be smaller than the main shaft - I could not find a shaft coupling any bigger than 6mm (the motor shaft is also 6mm). The rather strange (specific) dimensions of the main shaft (which is fully inserted into the flapper body) is, I believe, a result of it being US-made and hence of imperial measurements.

Happy to provide further info and clarification if required. Indeed I am all ears to alternative ideas too and/or suggestions as to who/where might be able to make this shaft for me.

Regards,

Reply to
Mathew J. Newton
Loading thread data ...

Rather than having a 15mm length of 6mm D section on the end of the main shaft it would be much easier to accomodate this in the coupling. Just drill it 7.6mm at one end and 6mm at the other then the shaft can be made in one operation. If also it's a proprietary size in the USA maybe you can find a length of it from stock and the coupling's then just a 5 minute job to make.

Personally I'd probably just make a small metal adaptor for the end of the plastic shaft you already have, bond this into place with araldite or similar rather than relying on a single grub screw and then just attach that to the motor. Alternatively make a coupling with a proper clamp for the plastic end and a grub screw for the motor end. There's got to be easier ways than making an entire D shaft from metal.

Reply to
Dave Baker

Where in the UK are you? (nearest big place).

Why not put a hole in the end of the shaft to take the motor shaft, and do away with the coupler altogether. That makes it simple to make, turn diameters and drill hole on lathe, then move to mill and create flat section, and whilst centered on shaft drill and tap holes for grubscrews. How is the motor / shaft end supported?

Dave

Reply to
dave sanderson

If the shaft was 8mm or 5/16" diameter instead of the od size,a half decent fitter could knock that out in 30 minutes with just a file. Can you not open out the hole to suit standard shafting? Mark.

Reply to
mark

Yes, I'm beginning to think that probably does make sense. I think I was of the 'safe' mindset of trying not to modify the bits I already had but rather to build what I required from scrap. Avoidance of any 'no turning back' situations I think!

I am perhaps guilty of underestimating the strengths of glue - lack of experience with the stuff I suppose. Indeed I'm wondering if I could make do with getting a 6mm shaft, filing off a flat for insertion into the motor coupling, and simply glueing the (undersized) shaft into the flapper on the dispenser? Again though I'm worried that once that's done there's no turning back - if it fails I've got a glued filled flapper to contend with!

Cheers,

Mathew

Reply to
Mathew Newton

Bristol.

I don't think the coupler is the probably as it grips the metal motor shaft quite nicely. I figured that if I can make the flapper shaft out of metal then I'd be laughing. Or was that not what you were alluding to?

The motor shaft is 6mm, with a 5.5mm flat (hence D-shaped), so any hole I

Do you think my real problem here is that I wanted the shaft stepped? I thought that this probably didn't matter, but now I'm wondering if it is in fact complicating things unnecessarilly!

The motor gearbox face has several M3 tapped holes so I was just going to using a metal bracket (from the Cisco switch actually!) to mount it to a backboard - the whole thing (dispenser included) will be mounted alongside (foregoing the stand supplied).

Mathew

Reply to
Mathew Newton

The flapper is an intriguing arrangement consisting of moulded rubber flappers surrounding a lump of plastic shaped to accept the D-shaped shaft.

Somebody did suggest getting some 8mm mild steel bar, putting it in my drill chuck and clamping the drill to the workbench. I then have something approach a lathe with which I could turn down to 7.6mm with a file. Taking this a bit further for the 6mm end I could then go on to manual filing the flat sections.

This sounds doable, albeit less-than-ideal hence I am holding out just a little bit longer. I do live near a one-man-band place that makes security products (chains, wall anchors etc) so I might pay him a visit to see if he'd be willing and able to knock what I need out.

Mathew

Reply to
Mathew Newton

Post item then.

Nope, I was thinkng how to make it easier. see a bit further down where I wrote simpler....

It is an extra complication, but there are many ways to skin a cat ;)

Ill head out to the garage now and see what suitable shafting Ive got lying around. drop me an email to snipped-for-privacy@googlemail.com

Dave

Reply to
dave sanderson

Mathew I will make you one this afternoon if you wish. Is a bit of printer bar ok for the material? Mail me direct addy is valid, with a phone number.

Richard Richard

Reply to
Richard Edwards

Gents,

Thank you - I have sent you both an e-mail.

Regards,

Mathew

Reply to
Mathew J. Newton

Thanks to Dave making the shaft for me (and with Richard in stand by!) the cat feeder is now up-and-running if anyone's interested:

formatting link
Mathew

Reply to
Mathew Newton

Aha! a use for surplus 1900 and 2900 switches :-)

Wait until a 3750-24PS is a junk switch and you could drive the motor (48V) with the POE from the ports. The possibilities are mindless :-)

Mark Rand RTFM

Reply to
Mark Rand

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.