Pre-war engine on an engine stand.

[Tony Fearn]

Hello all.

I'm just looking for a little engineering knowledge.

The family have 'clubbed together' to buy me a Clarke engine stand for Christmas, which I got last weekend as it was a 'VAT-FREE' day at Preston Machine Mart.

Now I knew that it would be rather difficult to mount the pre-war engine on it as there aren't many screwed bolt holes on the casing, so I am having to make a U-shaped angle-iron adaptor which will fit on the engine and the plate on the stand.

For two of the locating bolt holes I intend to use the oil-way brass plug holes just below the oil pressure valve at the rear of the sump below the gearbox attachment flange.

Now here's the rub.

I don't know what sort of bolt thread these oil-way plugs use. I've gently tried BSF, Whit and UNF bolts of similar diameter, but none of these threads will go into the holes. I can't use the actual oilway plug as it's far too short.

So I attach a photo of an oil-way plug, and having bought a thread gauge at a boot sale a few years ago, find that the gauge marked 1.25 fits perfectly into the grooves of the thread.

Can anyone suggest what bolts I should ask the local engineering supplies for please?



Thanks,

Tony.

P.S. Has anyone done this before? Am I re-inventing something??

[george garside]

Hi Tony

could it be BSP? Not sure of set up of clarke engine stand so can't comment on attachement point

george

[Keith Clements]

Threadsize 1/4
Threads per inch 19
Pitch 1.337

max size thread 0.518

So it is not BSP

http://en.wikipedia.org/wiki/Screw_thread
see Wiki

[Tony Fearn]

Thanks George,

I don't really know.

Thanks also to KC but the link spaced me out.

Threadsize 1/4
Threads per inch 19
Pitch 1.337

max size thread 0.518

So it is not BSP

I don't know where all these details came from, but I'm hoping someone will tell me simply what I should ask for.

Tony.

[Alastair Gregg]

Hello Tony, you could lose yourself for years in that site and still come out learning stuff. I'm a bit more simple, I suspect you already have one but I could e-mail a copy of the good old Zeus tables if it would help? Other than that I couldn't offer anything to help you out of this one>

[Tony Fearn]

Thanks Alastair,

I'd be very grateful if you could email the Zeus information. It might make some sense.

What does 1.25 mean on the thread gauge? I've seen other gauges at my Classic Car Maintenance nightschool, but these just show TPI. I know this because the male thread on my Flying Fox's radiator cap is 14 TPI.

Tony

[Mike Allfrey]

Dear Tony,

May I throw in my tuppence-three-farthing's worth?

Jowett Cars Limited were not entirely faithful to that fabulous thread -- BSF. I know for a fact that the so-called 5/8" Javelin PE oil feed banjo bolt is not BSF, nor is any known pipe thread. I know that New Zealand had a tap specially made for that one!

I wonder if JCL did the same trick with your oilway plugs? And, maybe, the Javelin 1/2" oil feed pipe banjo? I have only tried to match the 5/8" banjo thread for some oil cooler fittings.

The 1.25 you found on your thread gauge probably relates to a metric thread pitch. Is it a Moore & Wright thread gauge set? Some sets I have seen are dual imperial and metric sets and, if of not good quality, could be of very doubtful use. I have seen (and bought) feeler gauges and a thread gauge set at a swap meet that were of the dual measuring systems type. For example, upon checking the pitch on the gauge for a 3/8" BSF thread (20 TPI) the metric equivalent stamoed into the gauge, was a good 0.3 mm out! The gauge came from China and it has probably been back as scrap and come back again as something else just as dubious!

Try, if you can, a 1/2" Javelin Banjo bolt -- it may work. Unfortunately I have never had to research that size like I did the 5/8" thread. The tool maker who made my adaptors, handed them to me and said, "Never again."

He had great trouble getting the pitch right.

Hope this helps a bit.

Mike Allfrey.

[Mike Allfrey]

Dear Tony,

I forgot to mention in my comments above that the 1.25 thread pitch you mentioned is ISO metric fine thread for 10 mm and 12 mm bolts/studs.
Normal ISO standard pitch for those sizes is 1.5 (10 mm) and 1.75 mm (12 mm), so, there is quite a difference. Metric fine threaded bolts are not easy to find -- here in Oz, anyway.

I wonder if Jowett Cars Limited took Dr Fred Lanchester's advice on odd threads?

I have, along with John Blaze, some very fixed views on bolt threads. It makes me cringe to see an incorrect bolt or nut installed on a vehicle. My late father said that. the start of the decline of the British motor industry, was the adoption of the bastard American thread form.

I believe all that my father said, because he also said that politicians are a bunch of liars. I have found that out too, so my believing his comment on thread forms is reinforced!

Good luck with your quest for the correct bolts so that you can enjoy your Christmas present.

Best wishes,

Mike Allfrey.

[Drummond Black]

Tony, from the information that you have supplied, and I read that you have tried UNF , 1/2" - 20 UNF appears to be very close.

20 TPI has a thread pitch of .050". 1.25mm has a thread pitch of .0497"
!!

Was your 1/2 inch Dia measured with a rule or a micrometer ?

Worth some input .

[Forumadmin]

Dear Keith, From Mike Allfrey
I have been involved with Tony Fearn’s topic on Jowett Talk, Pre-War section, about the threads in the Jowett crankcase oil ways.
I wrote a lengthy reply just after Drummond’s last comment, but after submitting, it sort of disappeared.
The gist of my message was that I am now fairly certain that the thread form that Tony is looking for is British Standard Brass, ½â€

[Drummond Black]

I totally agree with Mikes statement regarding thread angle. I did not want to go into too much detail as was hoping for a bit more detail from Tony. Mike is probably more accurate in the fact that UNF was not available in Pre-war days. I was trying to find a bit of detail regarding " Cycle " threads as they have some strange forms. Still working on that.

Regarding Mike's request that someone should supply an alternator built into a dynamo. This is available, but the price, is around 500.00 pounds.
!!!!!!!!!!!

[Forumadmin]

Yes they came about when alternators were banned from Classic rallies so the clever boys made them inside the original dynamo cases. Othres like us just swapped them back on the last stage.......

Hence the detail in Jowettnet on the reversal method. This was needed in France on the Monte when the only replacement for the dynamo was a Mini alternator generously donated by a fellow competitor. It really strained my memory doing it at a stage end in the wet and cold. You received penalties for using an alternator, not that it made much difference to our position!

[Tony Fearn]

Hello again.

Thanks to all who replied to this post, - George, Keith, Alastair, Mike and Dummond, and please accept my apologies for not replying until now.

The reason is that tonight I attended my Classic Car Maintenance nightschool class again at Accrington and Rossendale College as I do once a week in term time.

I hoped that someone there would be able to study all your comments about the thread size and help me go forward as the class is taken within the motor vehicle and engineering department.

The upshot of these discussions is that the thread was identified and checked and it turned out to be a plain and simple 1/4" BSP.

We ran a tap through the holes in the engine casing, and the brass plug (picture in original post) fitted snugly into the die, so I feel there should be an apology on my part for saying the gauge showing 1.25 fitted 'perfectly' into the grooves of the brass plug. It must not have been so perfect.

Best wishes,

Tony.

[Drummond Black]

Tony, he whole objective of the discussions proves what the site was designed for. !! Discussion and problem solving. WELL DONE

[PAUL BEAUMONT]

Tony, just one further thought (from my Ibis hotel room somewhere in France!) Everyone has concentrated on your original question about the thread size without stopping to ask if the oil feed port is structurally sound enough to do what you intend. I an not 100% familiar with this area of a vintage engine, but I would be a little concerned about attaching an engine (that presumably you are going to do meaningful work on) to a stand using a tapping that was intended only for an oil pressure pipe or relief valve. Have you satisfied yourself that it is OK?