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Post by richardwilliams on Jul 10, 2015 16:40:35 GMT
I have discovered the reverser screw on my Norman Spink Brit was clear bodged with a RH thread - the builder used 20TPI 1/4 Whitworth.
Now the drawings say 16TPI square thread, probably impossible to obtain and even more difficult to cut on the lathe for mere mortals like me. I can get a LH thread 1/4 Whitworth at 20TPI from Tracy Tools. Any other views??
Thanks!
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Post by fostergp6nhp on Jul 10, 2015 20:41:54 GMT
It will work.
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pault
Elder Statesman
Posts: 1,500
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Post by pault on Jul 10, 2015 20:48:52 GMT
what sort of reverser do you have on the loco? If you have a mangle and it gives the correct indications then don't change it from right to left hand.
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jj
Active Member
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Post by jj on Jul 10, 2015 21:40:47 GMT
Doug Hewson does the correct LH square thread screw and nut, although they were out of stock last time I checked.
Regards, John
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Post by richardwilliams on Jul 11, 2015 16:00:34 GMT
Thanks guys for your responses.
There are one or two suppliers around who have 'some' stock of Doug Hewson parts left. I might try Blackgates (who supplied me with the DH reverser), otherwise I will use a LH BSW 1/4 inch.
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jj
Active Member
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Post by jj on Jul 12, 2015 14:58:44 GMT
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Post by Jim on Nov 1, 2015 12:54:34 GMT
The combination of Hewson's reverser thread and nut and his driver's reverser mechanism in the cab work perfectly in that the indicator drum matches exactly the position of the link as it raised and lowered.
Jim
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Post by richardwilliams on Nov 28, 2015 16:11:59 GMT
In the end Doug helped me get the right parts and as Jim above says, the thread and nut match the drum on the reverser. The whole lot works like a sewing machine now (although see the item on the original castings supplied for the Spink design - the alignment of the screw was a good 1/4 out. This took some cutting and welding to adapt the old casting)!
Richard
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cadser
Active Member
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Post by cadser on Apr 7, 2020 17:33:01 GMT
I have just read this thread after searching for info on the screw type in the reverser as i am currently building the correct type of reverser for the cab.
I was not aware that it had to be left hand??
Its not a problem as i can get left hand taps from a friend.
I see the post are a bit dated, Thank you for asking the question in the first place, it has answered all my queries.
Bri
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,988
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Post by JonL on Apr 16, 2020 9:18:04 GMT
I'm assuming it is an ACME thread type, that may be harder to source.
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barlowworks
Statesman
Now finished my other projects, Britannia here I come
Posts: 878
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Post by barlowworks on Apr 17, 2020 9:14:43 GMT
It is a square profile left and thread. I was lucky enough to get a Doug Hewson one from Steam Workshop a couple of years ago. I seem to remember someone covering it in one of the Britannia build threads, it may have been Jim or Springcrocus.
Mike
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Post by simplyloco on Apr 17, 2020 13:25:05 GMT
It is a square profile left and thread. I was lucky enough to get a Doug Hewson one from Steam Workshop a couple of years ago. I seem to remember someone covering it in one of the Britannia build threads, it may have been Jim or Springcrocus. Mike I made the LH ACME reverser screw in stainless, and screwcut the nut in bronze as well, which rendered a certain Chris Vine slightly dizzy! More a labour of love than an engineering masterpiece! John |
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