Amazon: New (to me) 1963 Volvo 122

[142 Guy]

Out of ignorance I need to ask what a 16x2 BSPT thread is? I thought BSPT was like NPT in North America, resolutely defined in terms of imperial measurements.

The OD interlock switch design was probably more a function of the transmission vendor rather than Laycock de Normanville. I believe that the Volvo M41 was Volvo supplied and the threads on the rest of the M41 are non metric as I recall so a metric threaded switch is odd.

[Othen]

Originally Posted by 142 Guy

Out of ignorance I need to ask what a 16x2 BSPT thread is? I thought BSPT was like NPT in North America, resolutely defined in terms of imperial measurements.

The OD interlock switch design was probably more a function of the transmission vendor rather than Laycock de Normanville. I believe that the Volvo M41 was Volvo supplied and the threads on the rest of the M41 are non metric as I recall so a metric threaded switch is odd.

BSP is British Standard Pipe - I don't know much about it, but it is still used on plumbing fittings (I suspect like NPT in the colonies). I'm also really surprised there is a M16x2 metric definition within BSP, in the 1950s and 60s Britain metric measurements were a novelty.

We seem to have uncovered a bizarre situation here. It sounds implausible but the evidence seems to this one item being metric on an otherwise imperial motor car. This needs a bit more investigation before I take the gearbox off just to find out.

Alan

PS. Does anyone know where the reversing light switch would fit on?

[Othen]

Originally Posted by Laird Scooby

A bit more information for you Alan :


... Four alternative options there, one of which confirms M16x2 which i admit i find strange too, considering Laycock de Normanville was a UK company and supplied many British car manufacturers of the 60s plus Volvo (who in the late 60s/early 70s often had more British parts than "real" British cars!) so i'd guess they did it for a marketing reason.

Useful for all Laycock overdrive owners to know theyre still produced for many newer cars and are easily and relatively cheaply available! Note the price difference between the first one at Rimmers and the second - same switch, different branding and packaging!

Not sure on the position for the reverse light switch on yours but if you do fit a manual switch, you will also need to add an easily visible warning light on the dash to comply with legalities.

This does seem bizarre Dave. It needs a bit more investigation before I take the gearbox off.

Re the reversing light switch: the green book (M40/41) talks about removing the connection to it, but does not show me where it fits on, which is not so helpful. I'd rather wire up the lights with a proper switch than one on the dashboard (with a tell tale of course). I hope some Amazon owner with reversing lights will take a photo of where the switch fits on.

:-)

Alan

PS. It seems even more bizarre that there might be Triumph Spitfires out there with just one metric component!

[john.wigley]

[QUOTE=Othen; ... I'm really surprised there is a 16x2 metric definition within BSP as well, in the 1950s and 60s Britain metric measurements were a novelty.

We seem to have uncovered a bizarre situation here. It sounds implausible but the evidence seems to this one item being metric on an otherwise imperial motor car. This needs a bit more investigation before I take the gearbox off just to find out.

Alan
[/QUOTE]

It happened more often than you might think, Alan, and caused more than a few 'problems'.

On completion of their first year, spent in the Training School, RR Apprentices received their basic tool box. Those qualifying in 1966, including yours truly, were the last to receive Imperial standard tools (e.g 0 - 1" mic) later years getting Metric (e.g 0 - 25 mm mic). It was also customary for engineering drawings of the period to be dimensioned in both units.

Regards, John.

[Laird Scooby]

Something seemed very wrong to me about a metric BSP - British Standard Pipe - thread. From what i remember, they were always Imperial threads, so i looked it up.



They're ALL Imperial measurements.

As such i checked the "G" threads - Gas (pipe) threads. Many of these are Metric but the nearest is M16 x 1.5 and also checked the normal Metric thread sizes :



Still no results! As such, i've come to the conclusion it's a deliberate oddball thread, used to prevent people using an "approximation" switch to overcome a faulty overdrive switch.

Maybe i'm right, maybe i'm wrong but either way it's not a standard thread for most use it seems.

[Othen]

Originally Posted by Laird Scooby

Something seemed very wrong to me about a metric BSP - British Standard Pipe - thread. From what i remember, they were always Imperial threads, so i looked it up.

They're ALL Imperial measurements.

As such i checked the "G" threads - Gas (pipe) threads. Many of these are Metric but the nearest is M16 x 1.5 and also checked the normal Metric thread sizes :



Still no results! As such, i've come to the conclusion it's a deliberate oddball thread, used to prevent people using an "approximation" switch to overcome a faulty overdrive switch.

Maybe i'm right, maybe i'm wrong but either way it's not a standard thread for most use it seems.

... maybe Dave, but it can't be that rare as Amazon sells a common user M16x2 tap;

https://www.amazon.co.uk/sourcing-ma...NrPXRydWU&th=1

I'm thinking that I will have to take the gearbox out (it looks really simple) and have this tap ready to have a go re-tapping the 5/8" hole. If there isn't enough metal left to do that I'll have to get the M16x2 helicoil kit I posted a link to above.

I can't help thinking there must be some common use for M16x2 to justify people making off-the-shelf taps and helicoil kits.

Curiouser...

Alan

[Laird Scooby]

Originally Posted by Othen

... maybe Dave, but it can't be that rare as Amazon sells a common user M16x2 tap;

https://www.amazon.co.uk/sourcing-ma...NrPXRydWU&th=1

I'm thinking that I will have to take the gearbox out (it looks really simple) and have this tap ready to have a go re-tapping the 5/8" hole. If there isn't enough metal left to do that I'll have to get the M16x2 helicoil kit I posted a link to above.

I can't help thinking there must be some common use for M16x2 to justify people making off-the-shelf taps and helicoil kits.

Curiouser...

Alan

That's probably true Alan but back in 1962 M16 x anything was definitely NOT common on UK shores!

As such, it would have been an oddball thread back then. It is commonly used on towball attachment bolts these days so in that respect, is fairly common. Back in the mists of time, they would have used 5/8"UNC or UNF instead for towbars etc. I wouldn't bother with the Sourcing Map tap from Amazon, instead i would go for :

https://www.ukdrills.com/hss-hand-taps-m16-2mm

Much better quality IME and the edge lasts longer too.

I strongly suspect you'll have to Helicoil it as the root of an M16 x 2 will be 14mm but you may just get away with it - perhaps a spot of Loctite 243 or similar on the threads to help lock it in place.

[Othen]

Originally Posted by Laird Scooby

That's probably true Alan but back in 1962 M16 x anything was definitely NOT common on UK shores!

As such, it would have been an oddball thread back then. It is commonly used on towball attachment bolts these days so in that respect, is fairly common. Back in the mists of time, they would have used 5/8"UNC or UNF instead for towbars etc. I wouldn't bother with the Sourcing Map tap from Amazon, instead i would go for :

https://www.ukdrills.com/hss-hand-taps-m16-2mm

Much better quality IME and the edge lasts longer too.

I strongly suspect you'll have to Helicoil it as the root of an M16 x 2 will be 14mm but you may just get away with it - perhaps a spot of Loctite 243 or similar on the threads to help lock it in place.

You are right, but it is worth trying the M16x2 tap to see if I can get a thread to hold, as you say a little bit of Loctite might be useful. It doesn't have to take much torque.

Alan

[Derek UK]

Note that the gearbox lid is very thin. That is why the use the tapered thread as it locks very quickly. I would think that is too thin to take a Helicoil. If the lid doesn't have a hole for the switch there is a ring cast into the underside where you need to drill the hole.

[packers1712]

Hi Alan,

I hope your inhibitor switch installation is progressing well, attached is a picture of where the reverse light switch is found on the M41 gearbox, strangely it is just a push in item and notoriously difficult to do with the gearbox installed but not impossible!

Doug.