Lotus Elan and Lotus Elan Plus 2 Forums

Hi all, Looking for the diff drain bolt size for an Elan S2.. It is not a 1/2'' and the 9/16'' is a little loose (don't want to strip the brass drain bolt) . So will a 17/32'' socket fit tight or is there another one that will.. I tried Metric and the same thing happened.. I can shave a wrench of 1/2' bigger but I wouuld rather use a socket.. Any ideas out in Lotus world..

Pic of area included

Cheers,
Lou

I believe it's bsp/whitworth. Which is why none of your metric or sae sockets fit.

You could but some whitworth told or make something....

It's probably a standard plumbers part.

Hi Lou,
Just checked my spare diff. and a 13mm socket fits perfectly. They are brass and easily rounded off so maybe that has happened to yours
cheers Alan P.

^^^+1 and make sure it's a six point socket.

I replace these with a hex socket BSP plug as easier to remove with an ball headed hex key in the restricted space

cheers
Rohan

The drain and filler plug on my car are 3/8ths Whitworth.

Lou,

My car is an S4 Elan. I have just checked my drain plug, confident it would be a Whitworth size. The best fit I have is 14mm across the flats!

As a Brit I feel I should apologise for the thread and spanner sizes we used to use here. Whitworth was an eminent engineer, and I believe he was the first person to standardise screw threads. For reasons that I don't understand he defined a spanner size by the thread diameter, so a 1/2" spanner would fit a 1/2" bolt, but the hex size was 0.920" across flats. Whitworth (BSW) threads are a corse series and are similar to UNC. BSW was followed by BSF (British Standard Fine) but the hex size for BSF is not the same as BSW and a 1/2" BSW spanner will not fit a 1/2" BSF bolt. To add to the confusion during the Second World War BSW and BSF hex sizes were standardised to the BSF hexagon. After the war we didn't return to the BSW hex but continued to use the BSF hex size. To this we added the final difficulty, we continued to double mark the spanner as both BSW and BSF so if you want a spanner for 1/2" BSW bolt you need to select a 7/16" BSW spanner.

Because our cars tend to have a mixture of fasteners I picked up a sheet from our Snap On salesman that is called "NUT SIZES and CORRESPONDING WRENCH OPENINGS". This sheet shows nut sizes from 5/32" to 3-3/8" across the flats with all the dimensions of metric Whitworth and BA nuts that fall within these two extremes. I have found this very useful, when I don't have the correct spanner, to see if I have an alternative that is close.

Sorry for this tangled British system,

Richard Hawkins

Well; Richard, that has really (not) clarified things. As a Chartered Mechanical Engineer, I'm willing to bet that you are not.
There was a time on this forum when only those folks who exactly what they were talking about commented.

Hi all.. As usual all your comments and knowledge about the subjects are very much appreciated and whatever systems used in the past were good then and now we progress.. I will look into the13 mm if I have one and the bolt is in perfect condition until I work on it..( hopefully not. )
Regards to all,
Lou

Hello again.. I just checked the 13mm socket and it is a little small though a 13.5mm would do Anyways can anyone give me the exact bsp/whitworth size socket and I will buy it .. Thats the best thing to do..

Regards,
Lou

In the best traditions of this forum RIchard sought to assist and did so with humour and courtesy which (along with plain English) appear not to be on the syllabus of Chartered Mechanical Engineers.
Gordon

Cool.. A little humor goes along way.. I have only respect for information and opinions on anything that relates to British engineering.. You guys are building Formula 1 race cars so it takes years of dedication and hard work to do that..

Lou

Now.. To the other important part.. I really need help on the actual size socket of the Diff drain plug please.. And if possible the Filler bolt though it is not as crucial..
Lou

Lou,
Speaking as an engineer, not an Engineer, I can say that the filler/level plug spanner size is 3/8 Whit (.710" A/F). For the drain plaug it's hard to be exact because I had to butcher it to get it out but I think it's 1/4 Whit (.525" A/F) . I would also add that replacement drain plug that I have (from a UK vintage car parts supplier) measures at approx .49" A/F. It was machined from solid so I was able to cross drill the head for locking wire.
Hope this helps a bit.
Cheers
John