Help needed for a complex (for me!) turning job.

[MikeWilliams]

Sorry this is not model related at all, but I need some help.  I've been involved with the restoration of a real carriage since the 1990s (its a long story!) and we are now completing the interior.  Although luggage rack brackets of various types have been found, none are the right pattern for our carriage.  So, we have obtained an official full size drawing and I've almost finished fabricating most of the pattern which will be used to cast the four brackets we need.  However, I am not clever enough to make the end knob.  For copyright reasons I can't publish the drawing here but the knob is basically an oval sphere with a large hole through it, the hole being offset to the extent that it breaks through for maybe 1/4 of the circumference.

A lathe larger than mine and with a ball turning toolholder would help, though the knob should really be oval, rather than round (may have to compromise there).  Please does anyone have one, and the ability to do the job?  CNC would be another option, but I don't have a CNC machine either.  The material doesn't matter and filler can be used because it is only a pattern for casting.  Solid printing would be too expensive due to the size.

Finally, the coach is owned by a charity but I'm personally happy to pay for this work.

Thank you.



Mike

[MikeWilliams]

P.S. very happy to send a copy of the drawing to anyone by e-mail, but not to publish on-line.

Mike

[John Candy]

When you say "oval", do you mean (sort of) egg-shaped?

Wood may be an option........ you can get wooden shapes turned to order or try yourseff (see links below).

turning an egg ..... https://www.youtube.com/watch?v=bryxCP0QTfs

apple .... https://www.youtube.com/watch?v=io7fP5csFNo

ready-made ....... https://www.acornwoodturning.co.uk/wooden-eggs/ (maybe they will make you a "special" to order).

Regards,
John.

[cabbage]

Mike,

When you say 3d printing would be too expensive - exactly how big is the handle? If it is a just going to be a master for a sand muller the the handle can be a "thin skin" hollow object of about 10-15mm thick...

Give me the dimensions and I will have a go!

Regards

Ralph

[Peaky 556]

Solid printing would be too expensive due to the size.

Thank you.



Mike

Mike,
Speaking as an observer of the art rather than as an expert, I am reliably informed that the interior of a so-called 'solid' print is normally set to print as a honeycomb of a much reduced density, thus saving a lot of material.  Whether it is worth reconsidering the printing of it will depend on the size of it and the advice you have already received.
Anyway, just thought I'd mention it...
Regards,
Tim

[Andy B]

Mike,
I have a ball turning attachment for my 5 1/2" centre height lathe - big enough?
Please send the drawing in this direction and I'll see if I think I can do it.

Regards,
Andy

[cabbage]

Tim is correct. I would simply produce a sphere and then distort the x,y and z dimensions to suit. The shaft is a cylinder or collection of frustrums.

I think your 3D print quote was for a "tank" system rather than a reprap system. CURA can be used to produce a number of densities of fill and a rough costing. PLA is roughly £10 per kilo.

Regards

Ralph

[MikeWilliams]

Thank you chaps.  I will copy the drawing asap and send to you.

Mike

[IanT]

Sounds like you are spoilt for choice Mike.

We have the Grandchildren this weekend, so we've not been able to pay too much attention to anything else (up at 6.21 this morning!)   

I have a ball-turning attachment for my Super 7 and you can do more than just straight spheres with it - but Ralph should be able to get it bang on if someone can 3D CAD the actual part for him.

Anyway, back to work. Playdough distracts them for a while - but it's a real problem getting the small bits out of the carpet afterwards I've found....

Regards,

IanT

[cabbage]

IanT - make Play Dough out of salt flour and water  with a little food colouring.  Once dry it can be hoovered out of the carpet.  Both of my sisters are NNEB  qualified!!!

But do not allow fimo or sculpy near leather furniture....

Regards

Ralph

[MikeWilliams]

Thanks again chaps - messages sent.

When working on a real vehicle all sorts of details are noticed, but often it is just not possible to incorporate them into a model.  In this case, although luggage racks sound nice in Gauge 3, in reality they are above the windows, so on a model you have to look upwards from below window level against the light coming from the other side of the carriage ... so I've omitted them from the model!

Mike

[cabbage]

these are "roughs" but the masters can be sanded from them!








According to CURA it will take 56minutes to print and cost 11p...

If you like I can print you a test piece. It might need slight scaling to get all the dimensions true. But once you have it in your hands you can caliper it.

regards

ralph

[MikeWilliams]

That looks just right Ralph, thank you.  I don't need the foot because I've already made that, but the neck and the business end look good.  Any chance of a spigot in place of the foot - say 4-5mm diameter?

Mike

[cabbage]

Could make printing a little difficult as it would all be pivoted on a 5mm stub(?) Let me try something and I will get back to you.

Regards

Ralpg

[MikeWilliams]

No problem Ralph - Although alignment would be easier with a dowel, its only one-off for a casting pattern and I am sure I can glue it together strong enough to make one rubber mould from it.

Mike