Author Topic: 3 1/2" Rob Roy  (Read 3841 times)

Offline Kim

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Re: 3 1/2" Rob Roy
« Reply #15 on: February 02, 2023, 05:25:22 PM »
That's a lot of work for those little guys!  But they are important pieces, so good that you've got them done!  :ThumbsUp: :popcorn:

Kim

Offline Dalboy

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Re: 3 1/2" Rob Roy
« Reply #16 on: February 22, 2023, 06:26:50 PM »
Back on the Rob Roy even if it is only making a pair of slide valve gland nuts, as I have been busy starting the vegetable garden off ready for the growing season. No pictures but it does feel great being back in the workshop hopefully more time in there

Offline Dalboy

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Re: 3 1/2" Rob Roy
« Reply #17 on: February 27, 2023, 06:47:30 PM »
Started to machine the ports on one of the cylinders today. Just need to drill the exhaust and 5 mounting holes which I will do while it is still set up in this orientation. Other jobes keep getting in the way so work is a little slow.
I have a white board whi9ch I draw the part onto with all the measurements in imperial decimal as the plans are in imperial fractional. Not only that but it means the plans stay clean.

Offline Dalboy

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Re: 3 1/2" Rob Roy
« Reply #18 on: February 28, 2023, 03:16:34 PM »
Well that is one step forward and two steps back so I have now ordered a pair of new cylinder blocks as I am not happy with the out come of the ones I have done so far rather than mess about trying to save them I decided to start again.
Not a total waste of time as I have learnt things from making them.
While waiting I will make some other parts or even do some work on the Farm Boy engine

Offline Kim

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Re: 3 1/2" Rob Roy
« Reply #19 on: February 28, 2023, 05:23:54 PM »
Sorry for the mishap.  That's never any fun   :(
So, what happened?  The last picture of the machined ports looked good to me.   :-\

Kim

Offline Dalboy

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Re: 3 1/2" Rob Roy
« Reply #20 on: February 28, 2023, 06:11:56 PM »
Sorry for the mishap.  That's never any fun   :(
So, what happened?  The last picture of the machined ports looked good to me.   :-\

Kim

I had already machined the surface too low before but was doing a work around, then this time for some silly reason I used the wrong size mill to do the outer ports they should have been 3/32" but I managed to do them 1/8" which means they are 1/32" over wide. New ones now ordered as well as a long series 3/32" bit.
At least it will solve two problems at the same time.

Offline Kim

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Re: 3 1/2" Rob Roy
« Reply #21 on: February 28, 2023, 08:16:43 PM »
Yeah, that's a tough one to recover from.  You could do a valve plate to cover the face and make that have the correct size openings.  I've seen that done before.  It might also help address the issue with the surface being too low.  But then again, sometimes it's just best to try again.

It's your engine, so you get to decide what the best path is.  And I'm with you either way!  We've all been there, done that.

Looking forward to seeing your progress when you get the new casting and the new end mill!

Kim

Offline Dalboy

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Re: 3 1/2" Rob Roy
« Reply #22 on: February 28, 2023, 11:33:40 PM »
I did plan to do that with the face that I machined too low and yes I could do that but I would not be happy I would rather start from scratch and have it right

Offline Kim

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Re: 3 1/2" Rob Roy
« Reply #23 on: March 01, 2023, 04:48:46 AM »
Sounds like the right call to me!  :ThumbsUp:

Kim

Offline springcrocus

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Re: 3 1/2" Rob Roy
« Reply #24 on: March 01, 2023, 07:59:31 AM »
Sometimes it can be down to cost. That looks like a very expensive lump of yellow metal in the vice.  :(

Commiserations, Steve
Member of a local model engineers society
www.stevesbritannia.co.uk

Offline Dalboy

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Re: 3 1/2" Rob Roy
« Reply #25 on: March 01, 2023, 03:40:56 PM »
Sometimes it can be down to cost. That looks like a very expensive lump of yellow metal in the vice.  :(

Commiserations, Steve

Total £67 for the two including postage. At least (touch wood) I know they will be right :Lol:

How is the triple coming on

 

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