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i have a 1980 t140e frame that i want to mate with an earlier (i think) centre stand which came with my 76 t140 (it came with 2 - one with the leg cut off (in the pic) and one unmolested - which is fitted to the 76)
the frame has smooth bores for the pivot bolt which is about 15/32 - not quite 1/2" - and a 7/16 bolt is sloppy in the hole
the stand has 7/16 unf thread
neither of these appear to be consistent with the parts books for the two years
so, i'm wondering if anyone knows of a bolt that will allow the union of these two apparently mismatched bits
i see in the 80 t140 parts book that its meant to use a 1/2" bolt, but this wouldn't fit the hole in the frame - i've already tried
i'm thinking a shouldered 7/16 unf bolt - but as always i'm happy to be informed otherwise
pics i hope will help
as always, i'm very appreciative of the help this family provides
rory
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Hi Rory,

frame has smooth bores for the pivot bolt which is about 15/32 - not quite 1/2" - and a 7/16 bolt is sloppy in the hole
stand has 7/16 unf thread
neither of these appear to be consistent with the parts books for the two years
'Tis consistent certainly with what's illustrated/listed in the second (August) edition of the '76 parts book - the 14-1304 nuts shown were 7/16"UNF Cleveloc self-locking nuts that are also locknuts in addition to the 7/16"UNF thread through the centrestand legs.

Then I'll add that the centrestand bolts are shouldered (similar to the sidestand pivot bolt in your previous thread) - nominal 1/2" OD through the frame then 7/16"UNF through the stand and locknuts. :)

Aiui, the original idea was the nominal 1/2" OD of the bolts should be slightly longer than the thickness of the frame lugs, then the bolts could be screwed into the stand and tightened but the difference in length/thickness would mean the stand couldn't be tightened against the frame and prevented from pivoting by friction. (y)

(n) In practice, between sloppy original manufacture and the pattern part makers, ime most (all?) off-the-shelf shouldered pivot bolts are crap - usually, the 1/2" OD length is shorter than the thickness of the frame lugs, making the overall length of the bolt too short, meaning not only can the stand be tightened against the frame so it doesn't pivot but also the thread doesn't protrude through the locking part of the self-locking nuts ... 馃槪 Also, even original bolts were turned from 9/16"AF bar, which is only just bigger than the 1/2" OD so tightening the locknuts starts to pull the bolt hex.into the frame lugs ... :rolleyes: You couldn't make it up ...

Fwiw, I turn centrestand bolts from 5/8"AF stainless hex. bar (5/8"AF is also the standard hex. size for 7/16" UNF (and UNC) bolts), making the 1/2"OD length not only slightly longer than the lugs' thickness but also allowing for a standard 1/2" washer between bolt head and frame lug, I also make the 7/16"UNF long enough not only for the thickness of the stand pivots and to have one or two threads protruding outside the self-locking nut when tight, but also for a standard 7/16" washer between centrestand and each locknut.

Another way would be off-the-shelf 7/16"UNF bolts to length required with 7/16" ID / 1/2" OD spacers also slightly longer than the thickness of the frame lugs?

Otoh, the '80 parts book shows a different arrangement - 14-1305 is a 1/2"UNF Cleveloc, which means the thread through the (different part number from '76) centrestand must also be 1/2"UNF. If 14-0147 is then an off-the-shelf 1/2"UNF bolt, it saved the Co-op the cost of making the shouldered bolts ... while allowing less ... uh ... thoughtful ... owners to tighten the centrestand against the frame ... 馃槪

Hth.

Regards,
 

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Discussion Starter #3
thanks so much Stuart
i dont have access to a lathe, so will go with locally available bolts 21-2077, be careful about pinching the lugs together if the shoulder isnt long enough and maybe split pin the bolt if its not long enough to accommodate the locknut
as always thanks for your insights
rory
 

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Hi Rory,

dont have access to a lathe,
:oops: I can see how "I turn" implies I have my own lathe ... I wish. I've always found a one-man-band engineer or machinist, sometimes retired with machinery in their domestic garage, local to wherever I'm living at the time.

First guy I found was courtesy of the workshop manager of the bike dealership at the end of the road - I was in there for something else, mentioned I'd broken a bolt on one of the T160's, he pointed at a building across the road (that I'd likely passed hundreds of times), said "Go round the back and you'll find Bob", Bob turned out to be a one-man-band engineer. When I got to know him better, he told me he used to make pattern Triumph parts in the early 1970's for someone called Les Harris, who was a mechanic in the dealership across the road ...

Over the years, word-of-mouth - bike or car garages/dealerships, local old bike and/or car club meets, etc. - has found most of the engineers/machinists I've used. When I moved to Scotland, in a bunch of small rural communities, asking owners of a couple of the local garages was how I found the local machinist, tucked away at the back of a small industrial estate about five miles away. Since then, the local parcel delivery guy has put me on to someone nearer with kit in their garage/workshop. (y)

Your Forum profile says you're in Sydney, no-one similar locally?

Hth.

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My lathe is a 30" bed Boxford from the 1960's (my Dad bought it from a college in Manchester about 30 years ago). It is imperial but I found an engineering company able to make metric main-feed and cross-feed screws and half-nuts. So, with about 15 minutes work I can switch between imperial and metric now. Happy days. However, turning and cutting bolts from Hex bar is a lot of work. I would recommend fitting a bush into the bike frame. In this case, I would drill out the frame to 1/2 inch, buy a couple of suitable 1/32" bronze bushes that are 1/2" OD, 7/16 ID and fit them to the frame. Then you can simply use a 7/16" bolt to fit the stand to the frame. Ideally, you want the bushes to be an interference fit to the frame, so you tap them in with a hammer. According to the table hanging on my lathe, a 1/2" interference fit is between 0.0003" and 0.0016". This would be much easier to make on a lathe than the full bolt with shoulders. Shame you are not close by as I would happily make them for you but there must be an engineering workshop near you that can help?

Stuart, I am interested in how you get your engineer to form the thread. Is it rolled or cut? I really want to get the kit to roll threads, due to the inherent strength of a rolled thread, but I can only find metric. I have an old Ferguson Triumph engine that has a huge torque requirement for the head nuts. I bought a set of modern copies but upon inspection under the scope they are definitely threads that have been cut. Considering I have to apply 130lb/ft to the 1,1/4" nuts, I am worried the stud threads will fail. If this results in the thread on the bottom of the stud failing (which is about 8" down inside a blind hole in the block) then the 70 year old engine will be a large paperweight.... Can your guys roll threads?
 

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Hi Ian,

thread. Is it rolled or cut?
Cut. I know rolled threads are stronger but, in practice, as all motorcycle makers use(d?) relatively low torques for the diameters (or, depending on your pov, large diameters for the torques) and most loads on the fasteners are shear, I've never experienced any problems.

Can your guys roll threads?
PM me the dimensions and threadforms and I'll enquire? If neither of the guys I use can roll the threads, there are a couple of precision engineering companies in Inverness?

My lathe is a 30" bed Boxford from the 1960's (my Dad bought it from a college in Manchester about 30 years ago). It is imperial but I found an engineering company able to make metric main-feed and cross-feed screws and half-nuts. So, with about 15 minutes work I can switch between imperial and metric
Mmmm ... that first engineer I used explained the same thing, most of his kit had been built Imperial but he had the necessary parts to change quickly to metric.

Hth.

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Cheers Stuart, will do. I think I have found a chap in Whitchurch who is able to roll thread. It is a proper old-school engineering company, the sort that are hard to find.

Rory; If you want some bushing and cannot find anyone local, let me know. Would be happy to make you some and post. I just need very accurate measurements of the hole so I can set up to make an inteference fit. Might take a couple of tries though...

Ian
 

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Discussion Starter #8
Ian and Stuart, thanks so much for your generosity of info and offer
i have found it difficult to source a small engineering shop here in sydney - the last job i put in at a bigger shop cost me $100 to turn a steering stem from 25.4mm to 25mm, so i'm still looking for someone who doesn't have to recoup big city living costs
i'll try the standard bolts and if that doesn't work out, i'll pursue the make options
thanks again
rory
 

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Realize that I am late to the party but I am confident the earlier stand will fit up just fine to the later frame. For the TR7, ,T140V and E there were two cstands used between 1973 and 1980..

You say that your machine is a 1980. If it is the brake caliper will be over the. Swing arm. If it's under the swing arm it is a 76 to 79 frame.

To properly mount the early stand you will need to obtain (2) 21-2077 pivot bolts and (2) 14-1304 nuts and a return spring.

If the earlier stand doesn't fit up I will be most surprised.

K
 

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Discussion Starter #10
thanks K
i think you're right - i've used a temporary pair of bolts and it seems to work ok
as you say, i intend to get a couple of the 21-2077 bolts and hopefully a more or less correct spring - fitting the spring to my 76 t140 is a frustrating exercise, but i understand this is normal
my 80 frame didn't come with a swingarm, so i'm using an earlier model item so that i can use my conical hub rear wheel - you can see the setup in my recent post on "what i did with my ..."
thanks again
rory
 
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