OT(?): Could somebody make a metal shaft for me? (for payment of course)

[Mathew J. Newton]

Hi all,

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:

cereal dispenser contains a rubber flapper mechanism which accommodates a plastic 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!):

you can see, the coupling to the motor (right-hand side) is required to be smaller 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,

Mathew

[Harry Bloomfield]

Mathew J. Newton formulated the question :

could file the flats on each end.

[Lobster]

Fantastic! Now there are 4 words I never thought I'd see in the same sentence...

Can't help I'm afraid; but isn't there a website out there somewhere where you can enter in requests for jobs like this, and people bid a price to do it? Don't recall any details but maybe someone else will?

David

[Mathew Newton]

Hi Harry,

To clarify, the shaft is D-shaped all the way along hence manual filing could be problematic...? This is why I thought a milling machine might be required...

(I can't believe I didn't mention it being D-shaped given it is such a fundamental point! Sorry about that...)

Mathew

[Harry Bloomfield]

Mathew Newton pretended :

I don't have such, but I thought the D shape was just to enable it to be firmly fixed at each end.

[Mathew Newton]

Unfortunately the design of the flapper is such that the shaft needs fully inserting - it thus needs to be flat across the whole length. I have modified the drawing to hopefully remove the ambiguity.

Thank you anyway for the initial offer.

Mathew

[Mathew Newton]

The result of requirements creep unfortunately!

Whilst it started out as a simple timer-controlled dispenser it soon became a bit more 'interactive'. It now has streaming video and a web- based interface...!

If I can get it up-and-running (the software is now written, and the electronics built) I'll be publishing details of the end result on a website so finger's crossed I can get this shaft sorted.

Mathew

[JimK]

angle grinder?

JimK

[Pete Verdon]

If you don't get any joy on that basis, there's always these guys:

believe they'll post to the UK and presumably the cost of sending such a small part will be minimal.

I also have a work colleague who is thinking of retiring and then earning some "pocket money" with jobs like this, but I'm not sure he'd necessarily appreciate me touting for business on his behalf just yet :-)

Pete

[The Natural Philosopher]

Go and find a robot wars supplier site.

Everything you need is probably there already.

a good read!

[John Rumm]

On could possibly avoid the milling operation by turning it down from square stock, and choosing your centre very carefully such that the right amount of flat is left on one side when the final diameter is reached.

I take it the smaller end is coaxial with the main shaft - therefore there is a step in the flat section at that point?

[Mathew J. Newton]

There is. Basically, the shaft rotates on a central line as if there weren't any flats.

Mathew

[Mathew J. Newton]

if you design it with their free software! Looking though at their samples prices it might still be a little steep though.

I'd be happy to be his first customer... And would of course put a link to his site (if he's going to have one) on my cat feeder pages! ;-)

Mathew

[Mathew J. Newton]

Yeah I've been all over that site - I was really starting to think robotics would be a great hobby to get into...

Unfortunately I didn't manage to find any suitable shafts... Basic round shafts (of not quite the right size!) and similar raw materials but nothing really close enough to what I'm after.

All good pointers and ideas guys though - I really do appreciate them.

Mathew

[Roger Mills]

Does it really need to be as accurate as your specification, if it only rotates slowly? Does anything have to slide along the D-shaped shaft in operation, or only in assembly. If the latter, can't you:

• Start with a length of 8mm mild steel rod

• Rotate it in a drill chuck, and use a file and emery cloth to reduce it to

7.6mm

• File the flat all the way along

• Bore out one end of the coupling - thus avoiding having to reduce the end of the shaft to 6mm?

[Mathew J. Newton]

Probably not. The measurements were just those obtained from the existing shaft. I didn't want to round anything off in case it resulted in it either not fitting, or being too loose for good grip (there is no grub screw arrangement in the flapper end - it just sits inside a D-shaped channel through its centre).

Hmmm... interesting. Do you think that would work? I haven't got a pillar drill - or were you just talking about a suitably-clamped standard drill?

I hadn't considered boring out the coupling either! I suppose though if I can form the rest of the shaft with my 'homemade lathe' as per your method above then I can just go a bit further with the small end..?

Mathew

[Graham.]

I'm intrested in the modified Cisco switch. Why is that needed?

[geoff]

In message , Mathew Newton writes

But why ?

Surely the flat is only required at each end

[geoff]

In message , Mathew J. Newton writes

It depends how urgent it is - I could prolly turn it down from a piece of 3/8" SS, but I'm not sure when I might have time to do it

[Nige Danton]

Ask in uk.rec.models.engineering lot's of very capable people there who could do this.

-- Nige Danton