Model Boat Mayhem
Mess Deck: General Section => Model Boating => Topic started by: Corposant on September 01, 2009, 08:47:07 pm
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I am about to fit the stern deck of a Caldercraft "Northlight". If I ever need to remove the horizontal steering pulley blocks (hopefully never!), then access to the 10 BA retaining nuts , via the deckhouse, is going to be a problem. A cranked ring spanner or flexible nut spinner would do the trick but I can't find anything that small.
The pics are of a mock-up showing the starboard side problem nut and the general layout.
(http://i949.photobucket.com/albums/ad338/photomultiplier/08_06_14_01117.jpg)
(http://i949.photobucket.com/albums/ad338/photomultiplier/08_06_14_01119.jpg)
I imagine this must be a fairly common problem. Any advice warmly welcomed!
Mike
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If you search on eBay for "strowger" you can sometimes find small specailist spanners.
None at the moment though :((
Strowger = old telephone exchanges
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Get yourself a bit of brass tube that just fits over the nut, put nut and tube into a vice, and squeeze the sides of the tube until it fits nicely around the nut. It will bend and shrink as you do it.
Then you will have a tube spanner that you can cut to whatever length you want, to make a socket, and solder any shaped handle onto it so that you can reach the nut.
I do this a lot when making my models, and for nuts of that size, they are plenty strong enough. I have also very easily filed specially shaped open ended spanners out of a piece of thin flat brass plate, for the same reason as yours. The handles can be bent and shaped to get into almost anywhere.
Bogs
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Dear Funtimefrankie,
Thanks for the Ebay suggestion. I will now be looking for Strowger telephone equipment - nothing if not intriguing!
Dear "Bogs",
I had thought of trying to "cast" the end of a spanner in epoxy - but your idea is much better! Many thanks.
Mike
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I am about to fit the stern deck of a Caldercraft "Northlight". If I ever need to remove the horizontal steering pulley blocks (hopefully never!), then access to the 10 BA retaining nuts , via the deckhouse, is going to be a problem. A cranked ring spanner or flexible nut spinner would do the trick but I can't find anything that small.
The pics are of a mock-up showing the starboard side problem nut and the general layout.
(http://i949.photobucket.com/albums/ad338/photomultiplier/08_06_14_01117.jpg)
(http://i949.photobucket.com/albums/ad338/photomultiplier/08_06_14_01119.jpg)
I imagine this must be a fairly common problem. Any advice warmly welcomed!
Mike
Whats 10BA in new money,i.e.mm as i,ve got lots of small sockets from 3mm to 10mm that you can have FOC
Wullie
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Wullie asks.......whats 10BA in new money?....well
From previous postings in PD's ......we understand.........
a) BA = British Association
b) whilst being British in terminology is based on metric units....[but not on simple whole number diameters ...x.0 units]
c) is 'semi' logrmetric in size designation....diameter > root diameter > thread pitch...all units considered >>:-(
d) so the BA thread form has the greatest ~~ strength~~ ratio :-))
So Wullie...from memory :o...10 BA is about 1.6 mm major diameter & 60 degree included V thread form.......I am sure another member will correct me here...or just GOOGLE .....BA thread form.........the six studs & nuts in the valve block attachment are 10 BA
Derek :-))
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Wullie, comprendez? Pete
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Derek,
Brilliant - I never knew that!!
Wullie,
Before you reach for your slide rule, 10 BA nuts measure 3mm across the flats so a 3mm socket would almost certainly do the trick.
Thank you both for your responses.
Mike
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I think you will find the thread form for BA is in fact 47.5 degrees, not 60. So not as close to metric as all that.
I think the range of BA threads stretches from 0 to 24 (or 26) I can't remember offhand, and was used as electricians threads for many years. It is now almost solely used for model engineering, where it can be used with great effect, because I think even the very smallest one can be obtained with hex heads, and a lot of the mid range ones can be bought with 1 size smaller heads, so you can have a larger stronger thread and still retain a scale effect by having the small head.
Bogs
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Well I knew that BA as not 55 degrees included & that......"I am sure another member will correct me here" ......thank you Bogs...as stating ......"BA is in fact 47.5 degrees, not 60" .....
mmmmm 47.5 certainly has a metric tone about it :-)) %%......Derek <:(
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I will check tomorrow morning if I have a 10BA socket, if I have its yours
Brian
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Hi
Why not put the screw up from under the deck and the nut on top of the roller.
The head of the screw could be glued in place to lock it.
Derek
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True to form,Mad House Mayhem srikes again,how a simple question can get umpteen different answers,and they were all wrong, {-)
and it take,s the Topic starter to cotton on to what i was on about,in the 1st place,
and for all you budding ingineers, what part of my question did you not understand,i.e. what is 10ba in mm {-) {-) {-) {-)
Wullie,who should have known better {-)
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The closest equivalent to 10BA would be a metric course thread of 1.6mm.
They both use the same thread pitch of 0.35mm. But of course, not the same form angle.
The attached chart shows the needed info
Bogs
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Derek,
Many thanks for your suggestion - a very good one but for the way I've made the pulley blocks! As you can see from the sketch, the sheave spins on a stainless steel pivot.
(http://i949.photobucket.com/albums/ad338/photomultiplier/08_06_14_01224.jpg)
Regards,
Mike
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Brian,
Many thanks for your very kind offer. If you find one, I should hang on to it - it must be a great rarity!
Regards,
Mike
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Hearty thanks to you all, I'm learning a lot about the BA thread!
Mike
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The closest equivalent to 10BA would be a metric course thread of 1.6mm.
They both use the same thread pitch of 0.35mm. But of course, not the same form angle.
The attached chart shows the needed info
Bogs
Bogs I,m going to Scream,AAAAAAAAAAAAArgh it was not the thread size i was meaning it was the nut size,e.g.Nutty problem??as this topic says, more AAAAAAAArghs {-) {-)
Wullie
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Here you go Wullie, http://www.sat.dundee.ac.uk/~psc/spanner_jaw.html
nice table at the end but there is some interesting reading in there too.
I never knew why whitworth spanners are labelled as they are, and that the nut AF is generally 1.5 times the bolt dia except for BA which are defined as 1.75x.
Since we hve wandered into BA territory the reason they are metric is that they are based on the swiss Thury threads for watchmaking.
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Hello,
Why not solder the nuts onto a small strip of Brass.
Screw the Brass strip under the deck, the nuts will then be captive and the screws can easily be taken out.
Engineering !!.
John.
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Although i was educated using Imperial measures,eons ago,i much prefer the metric measure,it makes life that little bit more simple,ok i know there,s fine threads and course threads,but on the hole its much easier to use,and at least i know that a 10mm socket will fit a 10mm head regardless weather it is a fine thread or a course,
unlike BA,BSW BSF etc,
I once owned a Triumph Bonneville,T140D 750,it was one of the ast mods to come out of the Meridian factory,before t was taken over by LF Harris,That bike had every thread imaginable including all the British bolts and also metric,and when it came to repairing it,which was frequent,the only gaurantee i had was that my metric socket set,would cover all the metric nut,unlike the British sizes,
No wonder Triumph,went down the tubes
Wullie
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Hi John,
Thanks for your suggestion but there are no screws involved! (See my sketch above.) I would have to rotate the whole pulley block and it would end up at an unpredictable angle. I'm also planning to drop them 1mm into the deck "planking" sheet to keep them steady.
Mike
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I still stick to my theory that a six inch nail and a bigger hammer will hold anything ( except a sky hook )
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Sky Hooks,now that brings back memories,along with "a long Stand,"and the left handed hammer,mmm,the joys of being a 1st year apprentice wood butcher, {-) {-)
Wullie
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Mike
I have had a look and my BA sockets only go down to 9BA, I have a 10BA spanner if that is any good in fact I have a whole set of BA spanners if you want them.
Brian
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Thicken the area under the mounting point with some 3mm plywood, and use blind nuts? O0
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Brian,
Thanks for the trouble you've gone to on my behalf - much appreciated. Thanks too for the offer of a BA set. I've actually got open ended spanners but anticipate a problem getting one on at the right angle in the available space. It's only going to be needed for the last half turn or so (a bit of plastic tubing will get them most of the way).
I'm being unbelievably pedantic about this because the chances are the blocks will never need removing!
Regards,
Mike
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Umi,
Thanks for the thought - but I can't screw the blocks in like a bolt - they'd almost certainly end up at the wrong angle! (See my earlier post with a sketch of their construction.) Or am I missing something in your idea?
Regards,
Mike
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Mike,
Take a look at the catalogue on this website, there are BA spanners and spinners: www.eileensemporium.com
Chris
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Chris,
Brilliant! Down to 16BA!!! Just the job. Their other stuff looks promising too!
Thank you so much,
Mike