I am making some replacement brass screw caps for the brass tube that houses the oil level indicator wire.
My initial measurements seem to indicate the thread is a 3/8th 26 tpi british cycle thread. I therefore made a sample with those dimensions, but it only rotates about five turns before getting stiff. Can anyone confirm what the thread is? I have just ordered a 3/8 die to chase the tube to fit, but don't wish to go ahead if there is better information out there.
Oil level tube screw cap
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Dhbangham
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- Given Name: Daniel
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BarryCambs
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Re: Oil level tube screw cap
Hi Daniel
By chance, my Engineer's Black Book is on the desk this morning. It shows a British Standard Brass with 26tpi? I'm not going to pretend I've heard of BSB before!
Barry
By chance, my Engineer's Black Book is on the desk this morning. It shows a British Standard Brass with 26tpi? I'm not going to pretend I've heard of BSB before!
Barry
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ian Howell
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From 1966 to '67 Black deLuxe Javelin LDF 738 (Scrapped with broken chassis)
From 1967 to '87 Black de Luxe Javelin MKC 1 (later 6469TU). (Sold as non-runner with tons of spares, 1987)
From about 1980 to '87 ex WD Jowett stationary engine. (Sold on)
From 1966 to present, 1930 Long Four Fabric Saloon, Dark Blue / Black.
Taken in a part-repaired state to the 2010 Centenary Rally, returned to a roadworthy state by 2013. - Given Name: Ian
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Re: Oil level tube screw cap
Yep! BSB is till used on some applications.
Interestingly? the pitch is 26tpi for all diameters.
This becomes pretty 'fine' on the larger sizes.
You should be able to get a suitable tap without too much trouble.
Interestingly? the pitch is 26tpi for all diameters.
This becomes pretty 'fine' on the larger sizes.
You should be able to get a suitable tap without too much trouble.
The devil is in the detail!
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Dhbangham
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- Given Name: Daniel
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Re: Oil level tube screw cap
Very interesting. I also had not heard of BSB. After reading the specification I quote below, I would say that Jowett would almost certainly have used the 3/8 BSB thread, not the BSC as I originaly thought. In practice, my BSC threaded caps have worked on two of the three engines I have tested it on. But on my first engine it was stiff, the difference between the two thread forms it that BSC is 60 degree and BSB 57 degree. Othersise they are the same at 3/8 diameter.
"BRASS THREADS (British Standard Brass)
Because brass tubing has a uniform wall thickness, irrespective of the tube diameter, any thread cut on, (or in) it, would have to have the same depth, so 26 tpi is standard on all diameters. An example would be the thread cut on the brass trumpet horns of the 30s cars, although many were die-cast rather than brass. If it were 1" O/D, the thread would be 1" Brass, 26tpi.
BSB has a 26 TPI pitch through the whole range and is often confused with BS Cycle thread the difference being that brass thread has an angle of 55 degrees whereas Cycle is 60 degrees. Brass threads are usually confined to fittings and adjusters on cables. Brass thread taps and dies are sold and advertised as 26 tpi and are identified by the letters BSB." coutesy of British Fasteners. https://www.britishfasteners.com/threads/bsb.html
"BRASS THREADS (British Standard Brass)
Because brass tubing has a uniform wall thickness, irrespective of the tube diameter, any thread cut on, (or in) it, would have to have the same depth, so 26 tpi is standard on all diameters. An example would be the thread cut on the brass trumpet horns of the 30s cars, although many were die-cast rather than brass. If it were 1" O/D, the thread would be 1" Brass, 26tpi.
BSB has a 26 TPI pitch through the whole range and is often confused with BS Cycle thread the difference being that brass thread has an angle of 55 degrees whereas Cycle is 60 degrees. Brass threads are usually confined to fittings and adjusters on cables. Brass thread taps and dies are sold and advertised as 26 tpi and are identified by the letters BSB." coutesy of British Fasteners. https://www.britishfasteners.com/threads/bsb.html
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Dhbangham
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- Given Name: Daniel
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Re: Oil level tube screw cap
So I managed to get a 3/8 BSB tap and die set and indeed it works perfectly. So I can now supply replacement oil gauge caps.
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Tony Fearn
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Re: Oil level tube screw cap
Hello Daniel,
I've followed this thread with interest.
Baden-Powell, of Scouting fame, coined the word 'stickability' as you probably know.
You must have been a Boy Scout.
I've just been over to the garage to photograph the caps in my collection, and here they are below - mainly for the record.
A: Part of the tube that comes out of the crankcase and guides the level-wire, showing the fine thread you mention. (3/8" BSB as we now know thanks to this discussion.)
B: A simple brass screw-cap as on my 1934 saloon with a knurled exterior.
c: A much more intricate, and aesthetically-superior brass type, also knurled. (Perhaps there was a chain attached so it couldn't be lost?)
D: Similar to C but made in steel. (May be a cost-cutting exercise?)
E: No prize for realising this is home-made in steel.
All the caps have a little pad of felt inside them to help sealing.
Click on the photo to enlarge it.
Perhaps a short article in The Jowetteer mag will keep Alan B happy, and be a life-line for anyone that needs to carry a spare. They're easily lost. Drop me a pm if you need the photograph.
Tony.
P.S. Is the BSB thread the one that's on the tie-bar to allow toe-ing in/out? - anyone?
I've followed this thread with interest.
Baden-Powell, of Scouting fame, coined the word 'stickability' as you probably know.
You must have been a Boy Scout.
I've just been over to the garage to photograph the caps in my collection, and here they are below - mainly for the record.
A: Part of the tube that comes out of the crankcase and guides the level-wire, showing the fine thread you mention. (3/8" BSB as we now know thanks to this discussion.)
B: A simple brass screw-cap as on my 1934 saloon with a knurled exterior.
c: A much more intricate, and aesthetically-superior brass type, also knurled. (Perhaps there was a chain attached so it couldn't be lost?)
D: Similar to C but made in steel. (May be a cost-cutting exercise?)
E: No prize for realising this is home-made in steel.
All the caps have a little pad of felt inside them to help sealing.
Click on the photo to enlarge it.
Perhaps a short article in The Jowetteer mag will keep Alan B happy, and be a life-line for anyone that needs to carry a spare. They're easily lost. Drop me a pm if you need the photograph.
Tony.
P.S. Is the BSB thread the one that's on the tie-bar to allow toe-ing in/out? - anyone?
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BarryCambs
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Re: Oil level tube screw cap
Inevitably, every one in the picture is different to mine. I'm always worried when I check the oil, as I think I read somewhere that the float will catch the crank if it is started with the cap off.
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ian Howell
- Posts: 963
- Joined: Thu Feb 09, 2006 10:46 am
- Your interest in the forum: From 1962 to '63, CA Bradord LLG 125 (Repaired and used).
From 1966 to '67 Black deLuxe Javelin LDF 738 (Scrapped with broken chassis)
From 1967 to '87 Black de Luxe Javelin MKC 1 (later 6469TU). (Sold as non-runner with tons of spares, 1987)
From about 1980 to '87 ex WD Jowett stationary engine. (Sold on)
From 1966 to present, 1930 Long Four Fabric Saloon, Dark Blue / Black.
Taken in a part-repaired state to the 2010 Centenary Rally, returned to a roadworthy state by 2013. - Given Name: Ian
- Location: Eastbourne, East Sussex, England
- Contact:
Re: Oil level tube screw cap
Back home for a while, tryingto get my pictures small enough to send to Tony, Nick et al.
Just to add to the fun, the brass cap on the oil level tube on my car has a round-head brass screw in the top, to which I have fitted a short chain, with a split ring (like a key ring) on the other end that fits over the tube to prevent it getting lost / dropped.
My cap is again different to all those shown.
I'm not sure about the risk of float damage in the event of leaving the cap off, but it is probably a good idea not to risk it! I seem to recall SOMEONE (no idea who) having a cork from a bottle pushed onto the top of the tube on their car!
Ain't Jowetteering fun?!
Just to add to the fun, the brass cap on the oil level tube on my car has a round-head brass screw in the top, to which I have fitted a short chain, with a split ring (like a key ring) on the other end that fits over the tube to prevent it getting lost / dropped.
My cap is again different to all those shown.
I'm not sure about the risk of float damage in the event of leaving the cap off, but it is probably a good idea not to risk it! I seem to recall SOMEONE (no idea who) having a cork from a bottle pushed onto the top of the tube on their car!
Ain't Jowetteering fun?!
The devil is in the detail!
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Dhbangham
- Posts: 75
- Joined: Sat Sep 21, 2013 7:47 am
- Your interest in the forum: Jowett long four owner. Jowett club member. (Former Armstrong Siddeley 20hp 1932 owner and ASOC member and former Lancia Belna 1935 saloon) Lanica owners club member. Interested in driving my cars especially in europe and making and repairing parts for the cars. I consider myself an oily rag owner.
- Given Name: Daniel
- Contact:
Re: Oil level tube screw cap
Thanks everyone for keeping this thread alive, I have been off grid for a while. It was the Login reminder that prompted me to look at what is going on. Thanks Keith for implementing that feature. I am not sure however that my feature "email me when someone posts a reply" is working.
Back to the screw cap.
Regarding the shape.... It is fascinating to try and work out how a design is arrived at. Boring, tapping and knurling are quick and easy processes, so your earliest example is cheapest and does the primary job. Someone was bound to realise that the caps got lost and needed to solve the problem. The installation of a ring and chain is the best option. So why did they not simply use a parting tool to create a simple groove to accommodate the ring and chain retainer? That would be cheap and quick. My hunch is that the prototype indeed had just that, but in practice the ring would not slide round easily in use, so it needed to be a v shape not square sided. Maybe the guy charged with improving the cap, made a chamfered groove and also decided to put a chamfer on the top face. That did the job, but he found it difficult to slip the ring over the end, so it eventually evolved into a ball as that was functionally the best and fulfilled an innate aesthetic sensibility. Thank goodness an accountant was not looking over his shoulder.
Anyway I have a couple of spare caps on my sideboard ready for someone to make use of. I will try and come up with an article as Tony suggests.
Back to the screw cap.
Regarding the shape.... It is fascinating to try and work out how a design is arrived at. Boring, tapping and knurling are quick and easy processes, so your earliest example is cheapest and does the primary job. Someone was bound to realise that the caps got lost and needed to solve the problem. The installation of a ring and chain is the best option. So why did they not simply use a parting tool to create a simple groove to accommodate the ring and chain retainer? That would be cheap and quick. My hunch is that the prototype indeed had just that, but in practice the ring would not slide round easily in use, so it needed to be a v shape not square sided. Maybe the guy charged with improving the cap, made a chamfered groove and also decided to put a chamfer on the top face. That did the job, but he found it difficult to slip the ring over the end, so it eventually evolved into a ball as that was functionally the best and fulfilled an innate aesthetic sensibility. Thank goodness an accountant was not looking over his shoulder.
Anyway I have a couple of spare caps on my sideboard ready for someone to make use of. I will try and come up with an article as Tony suggests.
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David Morris
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Re: Oil level tube screw cap
Hi all,
Tony's picture is lovely and illustrates how Jowett's seemed to change things by the week! Bless them! My WW2 Jowett stationary engine and generator ( now in a new home! ) used Tony's type 'C'. Yes, there was a short length of chain fitted to the groove in the top and anchored to the crankcase to prevent it being lost!
Happy Days!
David
Tony's picture is lovely and illustrates how Jowett's seemed to change things by the week! Bless them! My WW2 Jowett stationary engine and generator ( now in a new home! ) used Tony's type 'C'. Yes, there was a short length of chain fitted to the groove in the top and anchored to the crankcase to prevent it being lost!
Happy Days!
David