7mm The Derby Line - Rolling Stock

[dibateg]

Like an absolute dullard, I managed to screw up the eccentric sheaves, by reaming them after joining them together. Yes - you know what will happen, they sit wonkily on the axle...

So, in true DLOS fashion, I've turned up some more. The only thing I need to do is work out how to drill the off centre axle hole at exactly 90 degrees through the sheave. Anyone have any good ideas about that?

 

[Ian@StEnochs]

Ideally mount the stock in a 4 jaw chuck.

However if you don’t have one you can still use a 3 jaw with a bit of packing under one jaw to offset the stock.

I have done it by marking the centre of the off set hole on the end and adding packing under one jaw, small pieces of etch waste, until the centre lines up with a tailstock centre. Slow and steady drilling as there is an unbalanced rotating mass.

Ian.

 

[John57sharp]

I don’t have all of the right terms, but on my little Taig lathe I’m able to hold work in a
machine vice and put the drill chuck onto the driven end so that the work stays still and the drill turns.

getting it to be exactly 90 degrees may be an issue,but perhaps easier than a less square angle.

John

 

[Dave Holt]

Is another way to separate them and drill them individually under a vertical drill? You could make a simple jig to ensure the same offset on each item.
Dave.

 

[simond]

I think I’d take Ian’s approach, ideally a 4-jaw (look at Ozzy’s recent post for centering, neat trick) and I’d probably drill the axle hole first, then set up in the 3-jaw, skim & groove, and then part off.

not keen on using packing to offset in a 3-jaw, but it would work ok, just go gently, as if it slipped, it could come out.

 

[Lancastrian]

just go gently, as if it slipped, it could come out.

I was told that once....ahem

 

[dibateg]

Thanks chaps -
some good ideas to mull over!

Regards
Tony

 

[45609]

Use the three jaw chuck. Take one of the jaws out and reinsert it one pitch of the scroll further out than you would for concentric turning.

 

[Ian@StEnochs]

I never thought about doing that. Excellent idea, Every day is a school day!

 

[45609]

Here is a video that shows what I was talking about. Skip to about 50 secs into the clip to see it. Of course you will be restricted to the amount of offset afforded by the 3 jaw chuck scroll pitch but it might be acceptable. Just really showing that there is more than one way to skin a cat.

 

[dibateg]

Thank you chaps -
As DLOS used to say, the problem is holding the work - I soldered the eccentric to a section of brass, to drill them, but it wasn't very satisfactory. So the answer was to start again and use the 4 jaw independant chuck. That worked fine. I was nervous about parting them off, but just took the cut slowly and they came off fine. Once they started to wobble, stopped the machine and broke them off.


They are not as clean a cut as I'd like, but some I'll do some hand finishing to polish them up. Mucked up ones and scrap above, new ones below. So I'm feeling quite pleased with myself!

 

[JimG]

I never thought about doing that. Excellent idea, Every day is a school day!

If you've got a three jaw with reversible jaws rather than separate inside and outside jaws, you learn that quite quickly.

Jim.

 

[dibateg]

The eccentrics are now invisible... It was a bit of a fiddle to get the sheaves on the axle and the retaining disks on without soldering everything up solid. So the sheaves and the eccentrics were all blackened soldering. Although everything was free enough before assembly, it was a bit stiff afterwards, and my dear old friend Jonathan Matthews, he passed away recently I'm afraid, recommended WD40 for this sort of thing.. and it worked a treat. Those file marks need tidying up!

 

[mickoo]

Like an absolute dullard, I managed to screw up the eccentric sheaves, by reaming them after joining them together. Yes - you know what will happen, they sit wonkily on the axle...

You donut

Why didn't you ask me to send you some new sheaves, I had 100 machined and have plenty spare

But the machining exercise was good skill learning so probably better that way round.

 

[mickoo]

A rainy day gives me time to revisit the ROD, and it was time to progress the new cylinders. I like things to come apart, but I couldn't fathom a way of doing that, so they are glued on. However, I made the valve chest removable, two long 12BA screws attach it to top plate in the frames. The slidebar brackets are also removable, held in place by a 14BA screw. I should have believed Mick - you can get the leading drivers out with the slidebars in place! The bogie pivot is tempoary, whilst I work out a more elegant solution...

Mick - have you any close up pictures of the drain cocks?

It's nice to have a few hours at the workbench, garden, building repairs and other jobs have kept me away from it. Ah... the busy life of the retired...

View attachment 216416

Drain cocks are really simple, they're a small globe valve, I used some 0.8 mm copper wire and fed it through a hand rail knob, one end of the wire into the cylinder, the other end bent as the drain would be and the handrail stub turned inboard to attach the operating linkages.







I do need to find some pressure relief valves and stuff them in now it's back from paint, the kit ones were not quite the right profile/shape

 

[mickoo]

The eccentrics are now invisible... It was a bit of a fiddle to get the sheaves on the axle and the retaining disks on without soldering everything up solid. So the sheaves and the eccentrics were all blackened soldering. Although everything was free enough before assembly, it was a bit stiff afterwards, and my dear old friend Jonathan Matthews, he passed away recently I'm afraid, recommended WD40 for this sort of thing.. and it worked a treat. Those file marks need tidying up!
View attachment 216854

Loctite 603 is your best friend here, solder two sheaves together in the correct orientation, dab of 603 on the axle where the sheaves will go and then slip the sheaves on and twist the axle in the sheave to help the 603 spreed evenly, be quick as it'll grab those sheaves in a few seconds and then they're not coming off.

Fit the eccentric rods and then put a thin bead of 603 on the axle where it meets the sheave, slide on the cover disc and rotate to the correct angle and it'll grab it solid, too much 603 and it'll seep into the sheave/rod bearing and lock it solid, less is more.

If you do screw it up, apply some heat and it'll soften the 603 so you can disassemble it all.

 

[dibateg]

Double donut! Now you tell me!
But I did enjoy the achievement of machining them -that was good experience.

Thanks for the excellent details Mick, that is a great help.

Now I just need to find some spare time!
Regards
Tony

 

[Clarence3815]

Spare time?

What is that?

Bernard

 

[daifly]

It’s what you think you’ll have lots of when you retire!

Dave

 

[Clarence3815]

Hohoho.

You are so right. I`m up and about more hours in the day than I ever was when at work and STILL seem to make little progress.

Mind you I am on the cusp of finishing a project I started in 2008 which will free up space to get my Swiss model on the bench for remedial attention.

Bernard