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Richard_Blake
01-08-03, 22:54
Made a mistake. Got mixed up 'tween cms and inches, cut too much off one arm of the bronze prop shaft A bracket (actually a "V" - no cross-piece). Cursed loudly.

Best solution: shorten the shaft tube by about an inch to bring everything back close enough to the hull (quarter-mounted propellor on a smack hull) and incidentally giving me the clearance for a shaft anode, plus bring the A bracket mounting blocks better over a frame.
That means I have to tap threads further up it (the shaft tube): Whitworth 55 degree, 14 G on a 1.5 inch outside diam. bronze pipe. Totally unavailable here. Nice engineer said he could turn the thread on the pipe for me on his lathe, but it's glassed into the boat. Don't think Edith would enjoy the spinning experience.

SO: if I describe the A-bracket, perhaps someone can tell me who made/makes it. They may be able to help me with tapping equipment.

OR: does anyone have a 1.5 inch whit. 14G steel nut (also of course totally unavailable here) lying about I can beg or buy for undying gratitude, etc.. Then I can do the old trick of the clever diagonal cut in the nut which makes it into a thread cutter.

BORING DESCRIPTION OF A-BRACKET:
It's bronze, of a type formerly often seen. Probably installed new on Edith in around 1985. No maker's name, just the number 205 on the mounting plates. Cast mounting plates roughly 3.5 inches square, four countersunk screw holes for fastening to hull, with a bit sticking out to accept the arm of the A (or V) - this sticking-out bit is wider than the arm, with raised edges like a shallow channel, to positively locate the arm. Holes in channel bit tapped to take bolts through arm. The bronze arms (1 and 1/8th wide by 3/8ths thick) are not drilled when you buy it new, so you can cut it to size (ha,ha!) yourself then drill it . The lump at the lower end of the "V" containing the cutless bearing is in three parts - the middle one of which is integral with the arms; the rounded/slightly pointed section at the propellor end has two large flats so you (or Charles Atlas) can unscrew it with a very big spanner; the forward end has the water lubrication holes in it, and is tapped to screw on to the tube.
Anyone recognize it? Or did half-a-dozen factories all make virtually the same thing?
We in fact have a spare, brand-new and exactly the same, which we saw by chance in a second-hand chandlery and snapped up in case we ever came down hard on a hard place. I would prefer to go on having a spare though, in case we ever come down...... So I'd rather not use it to correct the stupid mistake, when all I need is re-threading (apart from a new brain, that is.).

I now have a great deal of respect for those clever people on this forum who manage to ask for help in no more than two sentences!

By the way, can one get superscript little high and low letters/numbers on internet posting pages in order to efficiently write fractions? What knob do I press?

Help!
Richard


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ParaHandy
02-08-03, 03:09
there's no doubt it is bsw? letter G sometimes defines bsp and bsp thread form is identical .... surprising but true although tpi is different ... what is the tpi and how much new thread do you need to cut?



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mtb
02-08-03, 09:07
I just looked at my Zeus book, Pipe thread has an od of 1.882 compared to whit of 1.5 the tpi for whit is 6 and the pipe thread is 11. I'l keep a look out as some times equipment like this does turn up. there's a company that auction off ex mod stuff the last auction I saw big tap and die sets but thats gone now the next one will be in about a month here's the web address
http://www.ramco.co.uk/

Cheers
Mick

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charles_reed
02-08-03, 10:01
If it's on sterngear of that date it is far more likely to be BSP than Whit (which really disappeared in the '50s).

I had exactly the same problem in Sevilla when I had a new propshaft made (55% of the UK trade price) - mine had the added excitement of being a 25mm od shaft with a BSP thread on that.

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Bejasus
02-08-03, 10:07
more likely to be BSP than Whit (which really disappeared in the '50s).

My boat built in 1963 had Whitworth bolts holding on the bilge keels.
Which reminds me, I still have 1-1/2 metres of 1/2" Stainless Whitworth threaded rod lying around.


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Richard_Blake
02-08-03, 14:35
Thanks for responses.
BSP is the plumbing stuff, right? Fairly course thread? The engineer I mentioned said it definitely wasn't that. He tried screwing various things into the A-bracket thread.

TPI is definitely 14 - I've got one of those little thread identification things a bit like a feeler gauge, different thread on every fold-out flat bit, but only has whit 55* and S.I. 60*. The one that fits like a glove says Whit 14G (7/16). I've measured the thread gauge against a rule to be double sure, and it's definitely 14 tpi. This all (14G 7/16) makes sense according to the whit. definitions in my ancient copy of Newnes Engineers Reference Book. But the outside diam. of the pipe is 1.5", measured with a plastic vernier calliper (ugh I know but doesn't rust on the boat).

So it seems this thread is/was usually used on a 7/16ths bolt? Used perhaps in this instance because you need a finer stronger thread on bronze? The fitting can only be screwed about 3/4 inch onto the pipe before the cutless bearing housing comes hard up against it.
I need to extend the thread between 3/4 to 1 inch, then cut off the surplus pipe.

Can't get to the boat today - will triple-check measurements tomorrow.

Perhaps the setup was made by a bloody-minded manufacturer who insisted on supplying pipe and bracket. Cut a unique thread on the lathe!
All the best,
Richard

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birdseye
02-08-03, 19:21
afraid it does look like a one off. at 1.5" or equivalent, metric fine is a pitch of about 8 tpi, bsf is also 8 whit is 6, bsp is 11, unf is 12, unc is 6.

7/8 bsp and 7/8 unf both have the same pitch of .0714 inch (ie 14) but are not the correct dia and have different (but not by much) thread depths.

can relate to your instinct to hoard your spare for a rainy day, but since your neck depends on the a bracket security, maybe that rainy day has come. suggest you keep your old bracket and contemplate the bodge if and when you damage the spare one you've put on to replace it.


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Richard_Blake
03-08-03, 09:15
You've all inspired me to delve further into Newnes (which I don't usually because I don't understand most of it) and I think I've found the answer - subject to further fine measurement today on the boat: Screw threads for steel conduits, BS 31, 1940, amendment 192. Newnes: "Screw threads on conduit couplers and fittings shall be of Whitworth form as described in B.S. 84.... The number of threads per inch shall be as set out in the tables."

Then the table specifies 14 tpi for 1.5" od conduit pipe.

Off to the boat now. Will report any measurement adjustments this evening.

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mtb
03-08-03, 17:05
I think it's worth saying, if my lath was set up with a set of gears then I'd cut to that rather than fret over this thread or that and spend ages sorting through to find the correct set . He cut the thread to suit what he was making and to be fair to the engineer who made it, the only reasone this situation has come about is by user error the original job was still good. I just brought a pile of 150 odd bolts that are 5/8" x 8" who cares what thread their best quality out of Davenport shipyard .
Hey that's a point if any one needs new keel bolts I'm the man to talk to the thread is witworth 5/8 11 tpi the bolts are 8.1/2 long. No nuts but I should be able to source those !!

Cheers
Mick

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Richard_Blake
03-08-03, 18:18
Yes, it is worth saying Mick, and you're absolutely right about user error. Birdseye is also absolutely right in suggesting that for safety I use my spare. I''ve got about three weeks with the boat in the shed before I have to make a final decision.

Regarding the engineer: he was stuck with the thread cut into the end of the A-bracket/cutless bearing fitting by the manufacturers. Our chance-discovered spare has the same thread. So he presumably knew what thread to cut, around 20 years ago. That's the basis of my hope of being able to cut it again! Which would be the most elegant solution.

Have just re-measured everything, and it does indeed come out as a whit-form thread, 55 degrees, 14 tpi, 1.5 inch tube - exactly as specified for the old steel conduit standard. So if anyone comes across it over the next couple of weeks....

Otherwise - no big deal, I suppose, now I've come back to earth from fury at myself for the mistake. Worst case - I use the spare and measure twice, as I was taught long ago!
Thanks all,
Richard

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Richard_Blake
03-08-03, 18:19
I messed up in the middle...Yes, it is worth saying Mick, and you're absolutely right about user error. Birdseye is also absolutely right in suggesting that for safety I use my spare. I''ve got about three weeks with the boat in the shed before I have to make a final decision.

Regarding the engineer: he was stuck with the thread cut into the end of the A-bracket/cutless bearing fitting by the manufacturers. Our chance-discovered spare has the same thread. So he presumably knew what thread to cut, around 20 years ago. That's the basis of my hope of being able to cut it again! Which would be the most elegant solution.

Have just re-measured everything, and it does indeed come out as a whit-form thread, 55 degrees, 14 tpi, 1.5 inch tube - exactly as specified for the old steel conduit standard. So if anyone comes across it over the next couple of weeks....

Otherwise - no big deal, I suppose, now I've come back to earth from fury at myself for the mistake. Worst case - I use the spare and measure twice, as I was taught long ago!
Thanks all,
Richard

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skipper_stu
04-08-03, 20:58
disappeared in the 50s bit, especially from you charles, i served my time as an apprentice in the pit from 64 to 69 and we were still using brand new whitworth bolts then. suggest he contacts gwil at llangollen motor museum who has loads of stuff like that or can source it,
stu

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skipper_stu
04-08-03, 21:00
sorry
www.llangollenmotormuseum.co.uk
stu

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Richard_Blake
04-08-03, 21:10
Thanks, Stu. Will do.
R.

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Forbsie
05-08-03, 07:08
Sorry to butt in sounding ignorant, Mick, but is that copper boat nails or are they summat else?

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mtb
05-08-03, 07:57
Hello Gordon
No mate the blighters are like this one below

http://homepage.ntlworld.com/boats/NAIL LIKE NEW up.JPG

It's going to hurt paying fortunes to the Glasgo nail company but so far found another 40ft of deck to replace I dont have the choice.
Tell you what though last week while having a dig I found some of the actual hull planking is Larch YIPPEEEE I thought and other grateful words, there's about 20ft at the mo which needs sorting and 9x2.1/4 oak would cost to many carb's . All the written stuff says Oak on Oak it could be just the area's where they dragged stuff in cos you can see the tell tale rust like stains that denote Oak on the timbers but if it's good I'm not toutching it and there's no way I'l drill test holes ..

How's the gearbox hunt going

Cheers
Mick

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skipper_stu
05-08-03, 21:16
thats what i said, in fact ive still got my whit ring spanners from the mid sixties!
stu

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Forbsie
05-08-03, 22:25
No gearbox for me, I'm on an outdrive. Got engine running for first time on friday and it sounds sweet as a dream. Unfortunately, in testing her I broke a flexible coupling so I'm going to have to replace the drive plate, hopefully without taking off the bellhousing. ho hum

I'll ask around here about those nails, you never know someone may have a stock of them. A guy 20 yards down the island had a folding windscreen that was just perfect for my boat and sold it for 25. Result. /forums/images/icons/laugh.gif

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mtb
05-08-03, 22:35
You jammy git, when I want or should I say need the bargains there's nout going .
What out drive are you using.
I might be lookinhg for a cheap enfield to put with a bmc so if you hear of a cheap un Gordon let me know.

I still have not emailed G/Nail I know it's gunner be tons aqnd tons ......

c ya
Mick

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Bejasus
06-08-03, 08:08
It may have been me you meant for the gearbox Mick. I am looking for a down angle gear box. But I will look out for an Enfield for you also.

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mtb
06-08-03, 08:55
Yep sounds like me that !!
Cheers

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