Lotus Elan

Lotocone Mount Modification

PostPost by: Frank Howard » Mon Apr 07, 2008 2:14 am

I've got the rear suspension out and I'm considering a modification to the Lotucone mounts I have not seen discussed in the archives. I thought I'd run it by the group before I begin.

First, drill a couple of large access holes through the fiberglass directly above the two nuts that are welded on the chassis that hold the two bolts (the ones with the thin heads) that hold the Lotocone mounts on.

Screw a couple of new bolts through the two nuts through the new access holes.

Offer up the Lotocone mount to the two bolts which are protruding through the bottom of the chassis and secure with nuts.

Tack weld the two nuts to the Lotocone mounts.

Remove the two bolts and the Lotocone mount will drop out.

Finish welding the two nuts to the Lotocone mounts without burning the rubber.

Assemble the strut assembly on the bench including the Lotocone mounts using a spring compressor.

So why would one go through all of this? Now you can offer up the entire strut assembly to the car with the spring already compressed as in a modern car. Have an assistant reinstall the two new bolts from the top side while you hold the strut in position. This has got to be much easier (and safer) than trying to compress the spring at the same time you are trying to install the strut.

The only possible drawback I have read was that Roger pointed out that the reason the heads on the original bolts are so thin is for clearence between the heads and the top spring perch when the Lotocones are compressed under heavy load, but the nuts I plan to weld on to the bottom could be the same thickness and I'll make sure that bolts don't protrude past the nuts.

Am I crazy or does this make all kinds of sense?
Frank Howard
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PostPost by: triumphelan » Mon Apr 07, 2008 6:36 am

I makes sense AND we all know you are crazy
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PostPost by: oldelanman » Mon Apr 07, 2008 7:27 am

Sounds like a possibility but there's a couple of things you may not have considered. If you screw through the original captive nut and then weld on your new nut you will effectively have locked in the bolt which may make removal difficult. Also you will have to drill out or remove the original captive nut before final assembly or you may tighten up on that and leave your lotocone loose below.

Your solution wouldn't work on my Spyder rebuilt chassis as the top mounts are different. The seatbelt anchor plate is integral with the top of the suspension tower and the captive nuts are not accessible from the top.

On the question of bolt head clearance those thin headed bolts are a bugger to get out - particularly after 37 years ! Does anyone know if you can get away with standard hardware ? At full hang (droop) on my chassis there is around 18mm clearance between the spring top plate and a standard bolt plus lock washer. For there to be contact the mount would need to fully compress and the solid rubber bit crush by a further 5mm or so - seems unlikely under normal road going conditions. Any thoughts?
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PostPost by: rgh0 » Mon Apr 07, 2008 9:32 am

With the small diameter rear springs and top cap I can assemble the strut and fit the bolts from below as they are not covered by the cap. You can also use standard bolts as no potential for the spring cap to hit. i use head headed cap screws as easiest to holt on ball headed hex key and fit the inside one that way

I presume Lotus had aq reason to use the special thin headed bolts so a clash must be possuble in a heavily loaded rear suspension though you may never encounter the load required to do it in practice.

cheers
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PostPost by: oldelanman » Mon Apr 07, 2008 10:35 am

I've been thinking a bit more about the bolthead clearance issue and done a few checks with the bits concerned.

Looks to me as though the thin bolt heads are not really necessary - at least with the original set-up - as the spring top plate will contact with the vertical flanges of the seatbelt mounting plate before it gets to the bolt heads. This flange is around 13mm deep so even with a standard bolt head at around 7mm plus the lotocone baseplate at around 3mm thick the bolt head would not stand proud of the flange.
Attachments
Lotocone mount 015.jpg and
Seatbelt mount plate - standard bolt
Lotocone mount 017.jpg and
Clearance with standard bolt
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PostPost by: bcmc33 » Mon Apr 07, 2008 12:01 pm

Frank,

Perhaps I?m missing something here.

This past weekend I completed the reassembly of the rear suspension having built-up the struts and driveshafts on the bench. A very simple one man job.

When I took them apart however, I dropped the struts by undoing the top nut and then removing the Lotocones from underneath. Had I not converted to smaller springs, I would have simply reversed this process.

Despite Buckland, I don?t understand the comment regarding the thin head Lotocone fixing screws ? I can?t imagine the Lotocones flexing enough for a standard head to hit the spring abutment plate. My car has 3/8 UNC standard head screws and not UNF as stated by Buckland, and with smaller abutments, its no longer a potential problem and much easier to assemble from underneath.
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PostPost by: Frank Howard » Mon Apr 07, 2008 6:52 pm

oldelanman wrote:If you screw through the original captive nut and then weld on your new nut you will effectively have locked in the bolt which may make removal difficult.

Roger,

I don't believe so. Once I screw the new bolts through the captive nuts, I plan to tighten them completely. Then I plan on fitting the seatbelt mounting plate over the two protruding bolts along with the Lotocone mount from underneath. Once these two pieces are in place, I'll secure them by screwing nuts to the new bolts. Once this is accomplished, I'll tack weld the nuts to the Lotocone mounts to hold them in position. At this point, I should be able to back the new bolts out completely and the Lotocone mount will fall out.

Thank you for taking the trouble of posting two pictures illustrating why the spring perch will hit the seat belt mounting plate flange before it ever hits the bolt. That's one less detail I'll have to worry about.
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PostPost by: Frank Howard » Mon Apr 07, 2008 7:16 pm

bcmc33 wrote:Perhaps I?m missing something here...When I took them apart however, I dropped the struts by undoing the top nut and then removing the Lotocones from underneath. Had I not converted to smaller springs, I would have simply reversed this process.

Brian,

If you undid the top nut without supporting the bearing carrier, the whole assembly shot to the floor like mine did. Perhaps you had the lower control arm connected and that helped to control the strut as it pushed down from the chassis.

When you put yours back on, as you have upgraded to the smaller diameter springs and perches, you should have been able to compress your spring on the bench and install the Lotocone on the strut before you installed it in the car. Once you had your strut in position, because you have the narrow springs and perches, you should have been able to secure the two Lotocone bolts from the bottom.

Those of us who are using the original diameter springs will have to install the Lotocone mount on the chassis before we install the strut. Then we'll have to compress the spring as we install the strut which is more dangerous. My proposed solution addresses this problem.
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PostPost by: oldelanman » Mon Apr 07, 2008 7:44 pm

Hi Frank,
I do undrstand how you are planning to do it but I would suggest that you drill a clearance hole in the captive nut first, then assemble with new bolt and nut and tack weld the nut to the lotocone. That way there will be no issues with bolt removal or fully tightening on final assembly.

I've just rebuilt my rear suspension and since the body is not yet fitted I was able to fully assemble the struts, springs and lotocones on the bench and simply bolt the assembly to the chassis - easy! I have used standard bolts with lock washers.

Best regards,
Roger
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PostPost by: saildrive2001 » Mon Apr 07, 2008 9:56 pm

I just completed the rear suspension rebuild with original dia. springs & a new shock insert. The job is really simple to do, be safe & use a strut spring compressor, this is the one that has two threaded rods & clamps that go around the coils. When compressed place on the bottom spring mount & lift the complete assy up through the lotocone. If you have difficulty getting the damper rod through the lotocone use a fine piece of wire through the hole in the damper rod & feed it up through the lotocone. You can grab the wire with a pair of plyers & pull the rod up throughthe lotocone. If you use a thin enough piece of wire the nut will go over it. I found that I could push the rod through the lotocone using the bump stop.
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PostPost by: tdafforn » Tue Apr 08, 2008 5:57 pm

I used the exact same method and it worked perfectly !
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PostPost by: Jason1 » Tue Apr 08, 2008 7:31 pm

Hi

Can you guys post a pic of your spring compressor, I found mine was tight on the strut.

Jason
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PostPost by: saildrive2001 » Tue Apr 08, 2008 8:59 pm

I borrowed mine from the local Canadian Tire store here in Ontario but that doesn't help you. Basically it consists of two threaded rods, each rod has a piece that hooks over the coil of the spring. One end of the rod has an hex which you can get a socket or wrench on. I found you had to play with the location of the pieces that hook over the coils to have clearance to remove them after you have the compressed spring installed. It took a little bit of thought & playing with it but not much. Remember to place the two rods diametrically opposite each other. The one I borrowed had a keeper pin at each clamp to stop it from slipping off the coil.
Hope this helps in the abscence of a photo.
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PostPost by: bcmc33 » Tue Apr 08, 2008 10:44 pm

Jason,

I got mine from Screwfix - you have a store in Colchester.

http://www.screwfix.com/prods/45986/Aut ... ressor-Kit
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PostPost by: Quart Meg Miles » Sat Nov 03, 2012 10:37 pm

I have a simpler solution to the problem you're trying to solve, which is how to keep the strut rod and spring cap under control while fitting the strut into the Lotocone. Certainly works for me:

Without the spring, drop the spring cap over the strut rod down to the bottom of its flat and drill a hole through the rod, starting from the flat, to take a lusty split-pin, just above where the cap sits. Compress the spring, pull up the rod and then fit and align the spring and cap over it and insert the split pin, wrapping the ends of the legs around the rod out of the way. You now have a single item to install.

Thrust the assembly up into the Lotocone, sliding the bottom of the strut onto a jack to lift it up until you can screw the retaining nut on. There is plenty of room under the Lotocone for the split-pin head and legs and plenty of metal in the rod for a hole.

You can now remove and replace the strut assembly without it falling apart and, in theory, without compressing the spring first but my split pins bend a little under full load and you certainly shouldn't attempt it with the stronger Plus Two springs.
Meg

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