Author Topic: Strictly.... “ Hot Air “  (Read 71677 times)

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Strictly.... “ Hot Air “
« Reply #330 on: November 04, 2018, 04:33:14 PM »
That looks a lot of heat and it seems a bit tight at the point where it stopped in the second video but you are almost there.

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Strictly.... “ Hot Air “
« Reply #331 on: November 04, 2018, 04:52:50 PM »
Well done Jo, I'd call that a run.

You definitely have far too much heat at the moment and heating up the sub base won't be aiding either.

The full size engines did have a tapered keyway into the crank disc, these were hammered in tight then machined flush. At half scale we didn't think this was needed but you could perhaps use a small taper pin instead?

I'm truly looking forward to a more lengthy video!

Cheers Graham.

Offline Dave Otto

  • Full Member
  • *****
  • Posts: 4693
  • Boise, Idaho USA
    • Photo Bucket
Re: Strictly.... “ Hot Air “
« Reply #332 on: November 04, 2018, 04:52:58 PM »
Almost there Jo, looking good. :ThumbsUp:

Dave

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Strictly.... “ Hot Air “
« Reply #333 on: November 04, 2018, 04:54:51 PM »
Jo are the links on the crank pin hitting the vertical links? think I can hear a slight knock when they come close and that is where the engine came to a halt

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Strictly.... “ Hot Air “
« Reply #334 on: November 04, 2018, 06:10:25 PM »
No the end of the screw on the crank vertical link was hitting the crank web where the crank had slipped out of the disc  ::)

In the meantime we have been looking at another Robinson  :-X

Jo
Enjoyment is more important than achievement.

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Strictly.... “ Hot Air “
« Reply #335 on: November 05, 2018, 01:57:28 PM »
Good grief Jo!

Are you a Gemini by any chance?

You haven't finished the bigger one yet.

Have you ever tried doing any " metal spinning " ? I used to make Brass spinnings to mend/replace parts for Tilley lamps. It might be an interesting exercise to try to make the displacer piston for the smaller engine from some thin stainless Steel sheet.

The method is simple, find a suitable solid blank of the right diameter, preferably polished, the " chuck " Cut a disc from your sheet Steel that roughly corresponds to the top and sides. Mount the form tightly in the strongest lathe you have then press the disc against it using the tailsock fitted with a rotating centre and a centred thick washer. You also need a vertical peg firmly attached to a horizontal bar that can be fitted into the tool post. This is your leverage point for the form tool.

I learned a few secrets from a local spinner, use a non ferrous form tool for ferrous materials and vice verse for non ferrous materials. The lubricant is nothing more than Fairy household soap ( Green ) block and dissolved in Paraffin.

The next stage requires a little courage but if you've done any wood turning in the past then you're half way there! The form tool needs to be both strong and long because you're forcing the metal to move over the form. Bring the lubricated polished end against the metal and by pushing and leaning against the peg you start to create heat. You can now start to manipulate the metal by pushing it away from you, the flat quickly becomes a cone. Keep forming the cone to a tighter and tighter angle until you can start moving the metal along the length of the " chuck " whereupon you've finished. Hopefully you've got some excess metal in the length to allow for a neat " parting " using a sharp pointed tool. The top cover can be done the same way but your " chuck " will need to be the diameter of the finished outside diameter of the body spinning.

I would certainly recommend a few practice attempts at forming metal in this way but the results can be quite rewarding. The spinning firm I visited were very approachable the boss said, 5 years to learn the trade, 7 years to learn the Art!!

Cheers Graham.

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Strictly.... “ Hot Air “
« Reply #336 on: November 05, 2018, 02:05:59 PM »

 if you've done any wood turning in the past then you're half way there!


That will put her off before she even tries it :Lol:

It would also be good practice for when the BB1 Cylinder covers need spinning :LittleDevil: I enjoyed doing it for my Fowler

As it happens Tiley are in the next unit to the timber merchants that I use for my hardwood.

Online crueby

  • Full Member
  • *****
  • Posts: 18557
  • Rochester NY
Re: Strictly.... “ Hot Air “
« Reply #337 on: November 05, 2018, 02:34:43 PM »
Graham, I have never tried it with steel, but did make some clock pendulum bob covers from brass. I had to stop a couple of times and re-anneal the sheet partway through forming over the outer edge, but it worked quite well.

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Strictly.... “ Hot Air “
« Reply #338 on: November 05, 2018, 03:57:29 PM »
Hi Guys.

Annealing, particularly with certain Brasses is almost a must. However, the choice of the Brass in the first place helps as there are many particularly suited to spinning.

Attached is a picture of our most ambitious spinning, one done professionally I must add. I did however make the collapsible chuck. The finished item fits the very popular collectable Tilley PL 53 storm lamp.

Alongside the Bronze and Steel " pushers "

Cheers Graham.

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 6133
  • Switzerland
Re: Strictly.... “ Hot Air “
« Reply #339 on: November 05, 2018, 07:41:52 PM »
That looks nearer to running than my diesel  :ThumbsUp:  :ThumbsUp:  A little bit more fine tuning and you will have a runner  :wine1: ( and not be sprayed with unburnt diesel oil  ::) )
Best regards

Roger

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Strictly.... “ Hot Air “
« Reply #340 on: November 18, 2018, 04:20:05 PM »
On the Polly Robbie the governor casting is not a casting  :disappointed: It is a bit of flat steel. So using the bit out of the centre of the base I set about making a Cast Iron governor part. First the centre was turned up with a shoulder to fit into a 16mm hole and then the bit of spare cast Iron faced and had the centre fitted. These have been loctited together


I had every intention of not only finishing this bit but also machining the cylinder when Bluechip arrived this morning. After a very nice visit by Dave, thanks Dave   ;D , I discovered that Dave had left a box of bribery goodies for Surus  :headscratch: but the sun was out....Minx has been getting restless and wanted to go for a drive.... so we visited my supplier who had a workshop Elf for me  :naughty:. On arriving home I discovered that someone thought I already had a workshop gnome so I was not (currently) allowed an Elf as well  :( so he has added them to his collection and given me the box of Jaffas as a consolation prize :noidea:

I will have to try again tomorrow to do some more on the Polly Robbie.

Jo
« Last Edit: November 18, 2018, 04:51:00 PM by Jo »
Enjoyment is more important than achievement.

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Strictly.... “ Hot Air “
« Reply #341 on: November 19, 2018, 04:44:11 PM »
Update on my Alyn Foundry Robinson: I am still thinking about a design for the burner. I have some bits and pieces that I could make something out of  :noidea:

In the meantime I have been machining up a cylinder  :naughty: the fist step was facing the bottom and back to give me something to square up with. Mr Silky then squared it up in his four jaw and bored the cylinder, turned it round and bored the governor hole (the Polly design does not have a governor  :( but mine will) Check the cover fits before taking down.

Mounted back in a vice the governor face was skimmed again to square it up to the bore. At this point I found the spacing of the threaded mounting holes left a lot to be desired so chose to move them in from 19mm offset to 16mm offset. I also drilled the cover while everything was set up.

Jo
« Last Edit: November 20, 2018, 12:55:53 AM by Jo »
Enjoyment is more important than achievement.

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Strictly.... “ Hot Air “
« Reply #342 on: November 19, 2018, 04:55:08 PM »
The governor cover was marked on the inside face with a marker and hacked down to leave some material. then the outside was filed first on one side then the cover turned round and you can see how far out of symmetrical the casting is. One side was much wider than the other so there was a fair bit to file off. To make sure there was plenty of material under the bolts I used buttons under the screws ( sorry no pic  :-[ ) and marker pen to show the progression of the filing.

I should mention that this casting like the others in this Polly kit has some hard bits: one of those was the mounting point for the governor cover

At the end of the day I have a cover that fits and a cylinder ready for a bit more work  :)

Jo
Enjoyment is more important than achievement.

Offline Admiral_dk

  • Full Member
  • *****
  • Posts: 3752
  • Sψften - Denmark
Re: Strictly.... “ Hot Air “
« Reply #343 on: November 19, 2018, 10:37:00 PM »
Quote
At this point I found the spacing of the threaded mounting holes left a lot to be desired so chose to move them in from 19mm offset to 16mm offset.

Looks like you made nice progress after finding a "compensation mod" that worked, as the end result won't give it away for anybody that haven't build one themselves  :cheers:

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Strictly.... “ Hot Air “
« Reply #344 on: November 22, 2018, 04:50:29 PM »
Thanks Per,

The Power Piston came as a slightly over length piece of Cast Iron. At 42mm diameter the spare material represented a useful piece of material for 38.1mm diameter piston rings should I need them so I decided to start by turning the gash end down to 38.5mm diameter and to hold the material by that for making the piston. The entire piston was turned in a collet leaving about 0.05mm extra for lapping with, ignoring the hole shown on the drawing it was tapped to take the small end and then parted off. The piston is still at this stage slightly over length and will not fit into the bore although it "thinks about starting".

Piston turning was done on a simple jig - a piece of spare steel turned down and threaded to match the piston with a shoulder, the piston was then screwed onto this and pushed tight against the collet and the end turned to length. Pulling the jig out of the collet allowed the piston to be lapped. My chosen lap was a stone held in my fingers and rubbed over the outside of the piston making sure it was in contact with the entire piston length at all times. As the piston comes down it is important to check the fit. Sometime you will find it goes in so far - this is either an indication of a non parallel piston or that the bore on the cylinder has a slight taper. To find out which one turn the piston round and try it in the other way. As you can see this one fits in both ways round the same distance which means there is a slight taper on the bore of the cylinder that was caused by using a car brake drum hone rather than one of Smelly's hones. This can be corrected with a little more honing of the cylinder. Finally the piston slides in and all is well.

I was hoping that someone would have come up with some ideas for making the burner using the bits I have for the bigger Robinson by now  :(

Jo


Enjoyment is more important than achievement.

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal