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WW1 Peerless lorry restoration

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I hereby name this Tappet thread BO, British Obscure, as suggested by Doug.   😏

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Posted (edited)

Gordon

Thanks.:blush:

Regards

Doug

Edited by dgrev

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2 hours ago, Minesweeper said:

I now have M8 x 1.0 pitch Nuts and Bolts - but remain puzzled! The nuts screw on the original Tappet thread comfortably and I would be perfectly content to use them as the locking nuts for future use. The bolts screw in finger tight to a depth of about 3/8" only but then they start to tighten which makes me think that this cannot be right - they should screw down to almost 1 3/8" length to be similar to the originals if this is the right size.

Further thoughts, please!

Tony

IMG_5886.JPG

Just wondering if they are either pipe thread for some bizarre reason, or, if they had been torqued and the threads stretched?

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If you try to interlock the original and the M8 thread do they fit?

 

25tpi is starting to look like a possibility. 

I think that the fact it goes in as far as it does implies a pitch error rather than a profile difference (eg ISO v SI or NF v NFJ)

 

25.7 TPI (0.99mm) pitch Holtzapfel thread?

you have the nut, so hete is how to measure the pitch very accurately:

Run the nut dow to near the head and mark one flat. 

Measure the gap with a calliper and zero it (or note the reading )

run the thread down 20 turns or more, using the marked flat to ensure an exact number. 

Measure the head to nut gap again, divide by the number of turns. 

 

I have a CNC lathe. I can make _any_ pitch of thread. Even if it turns out to be an 80DP thread (25.46479089470325TPI)

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It just occurred to me to check the threads on the studs in the Crank Case which hold the bronze castings down - described in the Parts Book as the "Valve Plunger Guide". Steve took the Bronze Guides off with the Cam Followers still in them - all complete -15 of the nuts came off easily and the last one came out bringing the stud with it.

The studs are 5/16" in diameter I would expect that the TPI on them to be either 18 or 22 - possibly 24 but I guess it will not surprise you now when I found that they are 20 TPI ! I have double checked this by trying 5/16" Whit/UNC/UNF, and BSF nuts on the studs but they do not fit. What am I missing?

What are we going to find when we get further into the engine, I wonder?

Tony

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45 minutes ago, Minesweeper said:

The studs are 5/16" in diameter I would expect that the TPI on them to be either 18 or 22 - possibly 24 but I guess it will not surprise you now when I found that they are 20 TPI ! I have double checked this by trying 5/16" Whit/UNC/UNF, and BSF nuts on the studs but they do not fit. What am I missing?

That looks close to M8 again, you know. 

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I am still leaning towards a "British Obscure" thread form.

On the US WW2 tanks with radial engines, the rubberless flexible piping is said to use a

thread form called (I think for lack of any known name) "US Wartime thread" - quite coarse and matching

nothing else.

It may just be that what you have is a WW1 equivalent or an in-house thread form such as our Aussie electrical.

Regards

Doug

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On 5/8/2019 at 10:52 PM, andypugh said:

It could be something completely special. Or an SI thread even, so ISO metric wont fit either. 

Metric isn’t impossible. About this time Morris were using metric threads with Whitworth head sizes in their engines. 

Morris bought the Hotchkiss armaments factory in Coventry and it was used to manufacture engines and gearboxes (going on memory). The reason for the metric threads was the Hotchkiss machine tooling was set up to produce parts in metric thread form same as the guns they had previously been producing. Hotchkiss being a French company. Some metric screws were still used in the engines of Morris Commercial during WW2, but checking parts lists only in certain locations.

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8 hours ago, dgrev said:

On the US WW2 tanks with radial engines, the rubberless flexible piping is said to use a thread form called (I think for lack of any known name) "US Wartime thread"

Not to be confused with the similar German “Panzergewinde” 

https://en.m.wikipedia.org/wiki/Panzergewinde

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The Morris/Hotchkiss thing affected Morris engines in MG cars certainly up to the post WW2 TC, and no doubt others. Metric (non-ISO) threads but Whit/BSF bolt head sizes!

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If you google 5/16x 20tpi the answer is a Uns thread . unified special 

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The link in my last post did not work, this one does, it is another publication from around 1936, explaining the the American screwthreads were standardised in 1928 but a lot of info on alternative pitches in it.

www.vintagemachinery.org/pubs/1617/3537.pdf

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On ‎5‎/‎7‎/‎2019 at 7:01 PM, andypugh said:

5/16 UNF is 0.3035 OD at 24tpi once you take in to account thread truncation. (5/16 UNEF is rather larger) 

https://docs.google.com/spreadsheets/d/1m5zkO9-SbQaYWbTPlQXJ2VA73Ys8WgWDrPk_rEukHc0/

It would be 0.3038" @ 25 TPI, which would fit the stated thread gauge better. 

As others have said, the engine predates the standards that we have tables for, and there is no need for those parts to be _any_ standard as they are not intended to be interchangeable fasteners. So the degree of crest truncation (or even rounding) might make up the difference. 

You might be able to figure something out by the shape of the roots and crests (flats or rounded) but that would take a lot of work with a shadowgraph for dubious benefit. 

Hi Andy.

25 TPI is the same thread as used on all the fuel connections on my 2 1945 Standard Tilly's which also stumped us but when we checked a bit further its a thread that 'some' car manufacturer's used in the 20s & 30s

 

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Don't fall into the trap of using Moore & $hite thread gauges - just place two of same from a pair of bunches against each other - you will see what I mean.  PITA  , but I always double-check longhand using a Stanley knife blade.

Starrett gauges are much more reliable.

-------------

25 tpi  is very near to  26 tpi  ,  don't forget  CEI   - as opposed to BSC that is also  26 tpi

CEI (Cycle Engineers Institute)

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S.F.   (French thread)

8mm  nom.    =  1mm pitch  ,  60 degree

This may give a clash with modern metric.

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On 5/9/2019 at 3:49 PM, Minesweeper said:

It just occurred to me to check the threads on the studs in the Crank Case which hold the bronze castings down - described in the Parts Book as the "Valve Plunger Guide". Steve took the Bronze Guides off with the Cam Followers still in them - all complete -15 of the nuts came off easily and the last one came out bringing the stud with it.

The studs are 5/16" in diameter I would expect that the TPI on them to be either 18 or 22 - possibly 24 but I guess it will not surprise you now when I found that they are 20 TPI ! I have double checked this by trying 5/16" Whit/UNC/UNF, and BSF nuts on the studs but they do not fit. What am I missing?

What are we going to find when we get further into the engine, I wonder?

Tony

Hi tony

I have shown all this to Father, and he said where we could we used original , but he had to put a tap down through ours and used high tensile screws, 5/16 if this is any help,

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Hello there!

Father has been up for the weekend and has brought the cleaned-up followers with him.

DSCN7857.JPG.f96b70a7ba45600ed33a055d3a9c95d7.JPG

I have had a look and am quite happy that the tappets are 5/16" x 26 tpi. If a 55° angle then they would be a BSB thread for which we have taps and dies in stock.

DSCN8276.JPG.61fc9f2739ac071279445be24782d984.JPG

As you can see, I fitted both by hand and they are fine. Stiff but no rattle. The male thread is a bit truncated though, which brings the OD down. If they are Slough Lorries spare parts then I expect them to be 55°. If they are original manufacture, then I guess they would be 60°. Three of the tappets are rusted away completely and four are bent. The nuts are a mixed lot too so I have asked Father to make up a complete new set from 1/2" AF hex and will case harden the heads on completion.

Trying to identify old threads without causing more damage can be challenging!

Whilst looking at the threads, I could see that two of the rollers are beyond use so I will make up some replacements. The pin they run on is secured by a cross-pin with the ends riveted over. First job was to drill out the countersink.

DSCN8277.JPG.7c5e597b73f1ebe30ab79ff8d7520769.JPG

DSCN8278.JPG.7f105552259666ce0dc1ca06fae5e6a2.JPG

Both pins came out quite esily with a pin punch.

DSCN8280.JPG.aac5211c90672dc35ae7b278783d5fad.JPG

The pin, of another weird dimension (!), Has a very nice oil groove cut in its underside.

DSCN8282.JPG.8c00b49f30949ed5ac068f2f0d337aba.JPG

I am getting the impression that this engine is quite nicely engineered.

I'll do the second one shortly and make up some new rollers from silver steel so that I can harden them.

Many thanks for all of your thoughts regarding the thread. I have now learned that 25tpi is used on Springfield rifles! Always something new.

Steve  :)

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Well, I made a meal out of identifying this thread and thanks to all for their input - Ruxy, you were right all the time with the BSB identification and why didn't I think of that one? Emma (Cornish Made), thank your dad for his memory of it when he did the Cornish Peerless all those years ago!

So now, we plough on again!

Tony

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Great, and that means I guessed rightly that Peerless Trading had their sticky paws in this too, as they surely would not have been a British thread originally.  😁

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6 hours ago, Minesweeper said:

Well, I made a meal out of identifying this thread and thanks to all for their input - Ruxy, you were right all the time with the BSB identification and why didn't I think of that one? Emma (Cornish Made), thank your dad for his memory of it when he did the Cornish Peerless all those years ago!

So now, we plough on again!

Tony

My first thoughts were a  "Sellers"  thread ,  however after consulting Zeus and other sources ,,

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I walked past the Peerless Crankcase a day or two ago and of course, the 1/2" studs which hold the cylinders to it are still screwed in it, and they caught my eye. I assumed that  the thread on those would be either 1/2" Whit or 1/2" UNC - it would have been but unlikely, I thought, but maybe 1/2" BSF or 1/2" UNF. Following my earlier confusion with the BSB thread on the Cam Followers and Tappets, I thought that I would check those studs! And guess what - they are 18 tpi - so none of the aforementioned threads!

Any thoughts on that one, please?

Tony

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13 minutes ago, Minesweeper said:

I walked past the Peerless Crankcase a day or two ago and of course, the 1/2" studs which hold the cylinders to it are still screwed in it, and they caught my eye. I assumed that  the thread on those would be either 1/2" Whit or 1/2" UNC - it would have been but unlikely, I thought, but maybe 1/2" BSF or 1/2" UNF. Following my earlier confusion with the BSB thread on the Cam Followers and Tappets, I thought that I would check those studs! And guess what - they are 18 tpi - so none of the aforementioned threads!

Any thoughts on that one, please?

Tony

1/2" 18 UNS ??

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