Lotus Elan

Alex Black's Window cable clamp screw

PostPost by: gherlt » Sun Feb 28, 2021 2:03 pm

Hello,
as Alex at present cannot supply more of his much acclaimed clamp screws and he was encouraging me to source them by myself, so I tried to do.
I bought sets of different M6 screw types, different materials, some with even a hole (length wise) in them, and then tried for myself.
Alex advised to have professional equipment, I can now confirm that with "consumer level" tools it is quite difficult. Even buying professional drills and taps, all more or less broke.
I then came up with a different aproach, I think a smooth one.

So, I went to a professional with a lathe, he is willing to do the work.
He is currently working on a steel screw replicating the Alex Black screw and will come back with an cost estimate for doing 50. I will update here as soon as I get feedback.

Now to my approach to the clamp screw:
The original screw catches the cables by the force of the nut "against" the window glass (with some washers in-between).
Alex Black separates that and uses a grub screw to hold the cable and a nut to fix the assembly to the window glass (less force on the glass).

My approach is a mix between the Lotus and Alex' one. Instead of using a nut, I use a shortened version of Alex' screw (about 10mm long), but the grub screw has a wide head and his length is exactly that needed to hold the cable. And the space between the heads is exactly that needed for window glass and spacers.
I was advised to do this in brass, as it is much easier to manipulate then steel.
The prototype does work quite well, so I would like to ask the more experienced people here what the think about this approach, about doing it in brass. Same question applies to the replication of Alex Black's screw, would it be OK doing it in brass ??

Here some pictures:

These are M8 screws made of brass, threads taken off, interior M4 thread, cross drilled hole for the cable
20210228_104809_HDR.jpg and

20210228_104817_HDR.jpg and

Shortened to correct length and head flattened to half
20210228_104943_HDR.jpg and

with washer placed
20210228_105508_HDR.jpg and

pressed on glass from below, wit cable and washers
20210227_120317_HDR.jpg and

assembly completed but not screwed down.
20210227_120409_HDR.jpg and
Last edited by gherlt on Sun Feb 28, 2021 3:45 pm, edited 2 times in total.
1964 S1 (engine ready, awainting body paint)
1967 S3 DHC (trying to recreate Alex Black's window cable clamp bolt)
1969 S4 FHC (engine worn ... )

Brian Bucklands 2nd edition available ! Look here: https://theelanman.com
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PostPost by: h20hamelan » Sun Feb 28, 2021 3:21 pm

Is the force on the cable equil between all contact surfaces?
I am midway restoring an old pedal bike, I have used some newer hard plastic directional plates under the crank. Toyed with a few different options. Though, I know not what would work best here.
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PostPost by: billwill » Sun Feb 28, 2021 3:22 pm

It looks to me to be too long and will foul on the metal frame or pulley spaces.
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PostPost by: Craven » Sun Feb 28, 2021 4:50 pm

Grade of Stainless is everything when it comes to machining, some grades, 201, will work harden making life difficult. Grade 303 is your best chance in taping the central hole, have a clearance diameter hole other than length of grub screw.
Brass is a machinist dream material.
Personally I think the original arrangement with correct soft copper and fibre washers suitable, using a stainless nut & bolt.
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PostPost by: gherlt » Sun Feb 28, 2021 6:11 pm

billwill wrote:It looks to me to be too long and will foul on the metal frame or pulley spaces.

It does not. And this screw is not yet perfectly grinded, it is crooked.

This is at the lower plate
20210228_174929_HDR.jpg and


This is at the top plate, tight, but still passes with no touches.
20210228_174815_HDR.jpg and
1964 S1 (engine ready, awainting body paint)
1967 S3 DHC (trying to recreate Alex Black's window cable clamp bolt)
1969 S4 FHC (engine worn ... )

Brian Bucklands 2nd edition available ! Look here: https://theelanman.com
gherlt
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PostPost by: gherlt » Mon Mar 08, 2021 8:25 am

Has anybody one of Alex Black's screw at hand ?

I would like to know the height of the screw head.
1964 S1 (engine ready, awainting body paint)
1967 S3 DHC (trying to recreate Alex Black's window cable clamp bolt)
1969 S4 FHC (engine worn ... )

Brian Bucklands 2nd edition available ! Look here: https://theelanman.com
gherlt
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PostPost by: elanner » Tue Mar 09, 2021 2:42 am

gherlt wrote:Has anybody one of Alex Black's screw at hand ?

I would like to know the height of the screw head.


Is this what you're looking for? About 95 thou. I'm sure 1/10" would be fine.

Nick

Elan-Alex_Black_screwhead.jpg and
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PostPost by: gherlt » Tue Mar 09, 2021 6:25 am

Great, thank you very much Nick !
1964 S1 (engine ready, awainting body paint)
1967 S3 DHC (trying to recreate Alex Black's window cable clamp bolt)
1969 S4 FHC (engine worn ... )

Brian Bucklands 2nd edition available ! Look here: https://theelanman.com
gherlt
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