Lotus Elan

Mounting Starter Solenoid To Firewall Securely

PostPost by: Stevie-Heathie » Thu Jun 08, 2017 6:24 pm

I now realise how "exciting" it can be when your solenoid is not secured properly to the firewall. I almost welded my new solenoid to the nearby carb when testing it out the other night, causing a brown trouser moment and much swearing in my garage.

I'd really like to avoid that drama again, and I'm not confident the wobbly self-tapping screws in their enlarged holes are a sustainable solution for keeping the solenoid on the firewall.

Surely these cars left the factory with a better solution than self tapping screws?

What do others do please?

Best
Steve
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PostPost by: mbell » Thu Jun 08, 2017 6:42 pm

On the +2 there are "Flat Speed Clip" on the inside that the self tapper screw through and provide a secure mount. They also provide the a way to secure the ground connection.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: Craven » Thu Jun 08, 2017 6:51 pm

I believe the original self-tappers had a backing plate on inside of the bulkhead, mine were rusty hidden under the felt.
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PostPost by: pharriso » Thu Jun 08, 2017 7:28 pm

Yes I recently went through this myself & fitted a Tinnerman (aka speed) nut to the outer most mounting. You can't really get to the back of the inner most screw as it also screws into the heater plenum chamber. I think I went up to #10 SS self tappers for both screws.
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PostPost by: prezoom » Fri Jun 09, 2017 3:03 am

If there is one thing I cannot abide, that's not having long enough arms to reach a nut/washer that goes on the end of a bolt anywhere there is a void or on the inside when I am working on the outside.

So, I decided to fix this problem once and for all. Think fixing solenoid, brake balance block, windshield wiper motor jacket, Plus2 hood prop, etc. I took a piece of 1/2" round stock, chucked up in the lathe, center drilled it with a drill appropriate to tap a 1/4-28 thread. Could be 6mm. Turned the outside to 3/8: back about 3/4 inches, and threaded it 3/8-24. Parted it off about .900" back from the thread, creating a Tee nut. Expanded the holes the body where the object to be bolted was originally fastened, to a hole just slightly smaller than the 3/8" outside threaded diameter. This allows the Tee nut to be threaded through the body. And the Tee nut is tight enough to make it possible to bolt the offending part onto the Tee nut. Then, at a later time, I get around to the back side and slip a fender washer over the exposed threaded section along with a lock washer or wavy washer and a 3/8" nut. If you have tightened the 1/4" bolt tight enough, the Tee nut will not turn when the 3/8" nut is tightened. From then on you can remove and replace the attached part with no fuss or bother. I also use small nutserts for things like relays and other small parts.

I counted up how many I would need, made them up, plus a coupe of extras and then bartered some other lathe work for having them zinc plated, so they would not rust. If anyone is interested, PM me an email and I will forward a picture.
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PostPost by: MarkDa » Fri Jun 09, 2017 7:47 am

I've got a short strip of copper busbar with a pair of spire clips behind the bulkhead.
This provides good security without having to fiddle too much amongst the wires etc behind the dash.
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PostPost by: mbell » Fri Jun 09, 2017 6:46 pm

Another solution would be a "rivnut", which is basically a rivet with thread down the middle. They also do rubber ones which would be less permanent version.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: bob_rich » Sat Jun 10, 2017 8:57 am

Hi Steve

I made up a small aluminium plate with two "hank nuts" riveted in. Then this plate was pop riveted into position so that the solenoid could be taken off and / or replaced without the need for long arms. There were a lot of holes in my car bulkhead including a second set of holes for what looked like fixing the solenoid higher up- not sure of the history of this but I filled these and other unwanted holes with pop rivets. You could also try a small copper of brass place and solder two steel or brass nuts in and this would do just as well.

Have attached a photo

Hope this helps

Best of Luck

Bob
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PostPost by: alan.barker » Sat Jun 10, 2017 9:30 am

Maybe a stainless plate with 2 stainless studs welded on to mount the Solenoid on.
Like you say revit plate to bulkhead.
It would be nice to have the Solenoid fitted solidly and with a good earth.
The original way they were fitted was very bad and causes problems with the earth connection.
Alan
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PostPost by: Chancer » Sat Jun 10, 2017 10:10 am

Most elegant and sure solution is the doubler plate with Hank nuts or Pemstuds but you may see the plate.

Most aesthetic are rivnuts but the ones that have the best fixing have a small flange that will space the solenoid or whatever away from the bulkhead and the component may wobble and flex/crack the fibreglass.

I use Avdel thin sheet nutserts which if fitted with care give a flush and very secure rivnut fixing but they are not quite as resistant to turning in the hole as flanged rivnuts are so some common sense is needed when tightening or releasing a fixing, as the name suggests they are made for sheet metal but work very well in fibreglass.

Yes there are rubber captive fixings (an insult to call them rivnuts) there are also things called cheville molly (forgot the name in English) made for plasterboard but IMO these sort of fixings have no place on a vehicle and just show to anyone that the owner or PO was a bodge artist, before anyone comments I have heard that Lotus used them :D but then they also used touch latches for the glovebox, I have just fitted the last 2 of 10 of these to wardrobe doors in my apartments where no-one can accuse me of bodging!!
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PostPost by: alan.barker » Sat Jun 10, 2017 11:51 am

"cheville molly" is a trade mark like "rawlplugs" not a part identification :)
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PostPost by: Elan45 » Sat Jun 10, 2017 3:53 pm

I was always concerned about a frontal accident causing the solenoid terminal to touch the back carb, we're talking about since the mid-70s. I also was unhappy w/ the starting circuit and slow starter speed, so I finally plopped for a pre-engaged oriental gear reduction starters modified by Keith Gustofson. Then I removed the old solenoid and bolted the two cables on the old solenoid together and insulated the connection. I then made up an extension wire from the existing trigger to the location on the new solenoid of the gear reduction starter. It works wonderfully. Cranks well on the same battery that would barely get one or two turns w/ the old Lucas Bendix drive and I have no bulky electric source just behind the back carburetor. A win-win situation!

Roger
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PostPost by: Davidb » Sat Jun 10, 2017 5:03 pm

Being low-tech I simply removed the grill over the heater plenum and epoxied a nut on the inside of the firewall--it seems to work but I don't intend taking the solenoid off too often...
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PostPost by: Stevie-Heathie » Fri Jun 16, 2017 5:41 pm

Flat speed clips and self tapping screws installed. Job done.

Thanks all. Love this forum.

Steve
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