Lotus Elan

Tubular Anti Roll Bar

PostPost by: 1owner69Elan » Fri Jul 27, 2018 8:51 pm

I am interested to find out the wall thickness (or ID) for the tubular anti roll bars on offer. I want to calculate the effective stiffness of the tubular ones (compared to a solid one). I contacted the UK supplier (Kelvedon) regarding their 22mm and 1" tubular ARB's but no response yet.

I think there is at least one forum member that has Kelvedon's 1" tubular ARB. I figure if one measures the thickness of the flat tab on the end (where it attaches to the shock unit), that would give a reasonable idea of the wall thickness. The tab appears to be formed by crushing the tube flat on itself which would then make the tab thickness ~2 x wall thickness.

If anyone has the occasion to measure this tab thickness on their tubular ARB it would be much appreciated.

tubular-1-22-arb.jpg and
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PostPost by: 1owner69Elan » Tue Jul 31, 2018 6:48 pm

I received the information from Kelvedon regarding tubular ARB's and thought I would share it for the record:

1. 22mm tubular ARB: wall thickness 2.2 or 2.5mm (probably 2.5)
2. 1 inch tubular ARB: wall thickness 3 mm (~1/8in)

What this yields is:

1. The 22mm tubular is effectively a little less stiff than a 13/16 solid bar, but also ~5 lbs lighter than the 13/16. (22mm tubular is ~1.6 x stiffer than the stock 11/16" Elan)
2. The 1" tubular is effectively a ~23mm solid bar, a little more than the 7/8" (22mm) solid, but ~5 lbs lighter than the 7/8" (1" tubular is ~3 x stiffer than stock 11/16 bar).

The other thing besides weight savings, is that the tubular ones have mounting blocks on the lower part of the drop links instead of just a metal collar (metal to metal contact, needing grease - seems a bit rudimentary - OK for racing but not as good for the street?).

Bushings are used for the top part of the drop link to chassis connection in all cases, solid or tubular. The stock bar of course uses bushings on both top and bottom of the drop links.
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PostPost by: 1owner69Elan » Fri Aug 10, 2018 6:07 am

Well I received the 1" tubular (hollow) ARB from Kelvedon.

As I unpacked it, it seemed rather light.

I found that the tube, weighs only a bit more than 3 lbs. Less than what I had expected which was ~4.8 lbs.

aeb3b3d5-df8e-4197-b060-bcaede6c68c2.jpeg and


I inspected the crimped end of the tube where I could see the wall thickness of the tube. To the naked eye obviously much less than the 3mm that kelvedon specified.

I have determined that the wall thickness is somewhere between .072 and .083 inch (gauge 15 or 14).

The net result is the bar is both lighter and less stiff than anticipated. Basically somewhere between an equivalent 13/16” (26r spec) and a 7/8” solid bar. So about 2+ times stiffer than the stock Elan 11/16 bar.

I was a bit worried that a 3+ stiffer bar, which the larger 3mm wall thickness represents, was going to be too much, so this may work out OK.

In any event, for the record, the 1” tubular bar is not as stiff as portrayed. But, also less weight.

We’ll see how it feels on the road.
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PostPost by: Davidb » Fri Aug 10, 2018 3:33 pm

Looking forward to hearing how it feels when driving. Do you feel like sharing the cos, including shipping?

I have an Addco 7/8 bar that I bought about 18 months ago but have not fitted because the mounts Addco provided are like regular sway bar mounts and fit the bar directly to the bottom flange of the chassis--does anyone have experience of using one of these Addco bars? They still have them available apparently.
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PostPost by: 1owner69Elan » Fri Aug 10, 2018 5:07 pm

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PostPost by: 1owner69Elan » Fri Aug 10, 2018 5:29 pm

Weight data:

1" tubular ARB w/o links: 3.4 lbs (Stock 11/16 bar ~6 lbs - but I will weigh when I swap out)
Drop links: 0.94 lbs

Again, I particularly like these drop links as opposed to the metal to metal collars on the larger ARB's.

img_0309.jpg and
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PostPost by: Davidb » Fri Aug 10, 2018 7:21 pm

Those links certainly look the business.

My Addco sway bar mounts look like this and require four holes in the bottom chassis flange:
img_0249.jpg and


Since we are talking ARB/Sway bars I thought I would add this: For the past 18 months I have been driving with a stock front bar and an original 26R rear bar--against all advice! I should add that this means driving in atrocious conditions at times, on narrow winding roads and, most recently, with the rear tires bald! I thought I would try it and have not had any adverse experiences.
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PostPost by: rgh0 » Sat Aug 11, 2018 2:35 am

Davidb wrote:Those links certainly look the business.

My Addco sway bar mounts look like this and require four holes in the bottom chassis flange:
The attachment IMG_0249.JPG is no longer available


...)


Unless you put a movable link on where the bar ends joins the suspension you cant mount the bar rigidly to the chassis. The drop links are needed so the bar can move back and forwards as the suspension moves up and down when the bar is connected to the bottom of the front shock using the standard stud on the bottom of the shock

I actually use a mount like you show but with a flat plate bolted to it and a modified section of a standard drop link with the bottom loop removed welded to the top of the semi circle

split-roll-bar-link-2.jpg and

split-roll-bar-link-1.jpg and


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PostPost by: Davidb » Sat Aug 11, 2018 2:48 am

Thanks Rohan. I did not install this bar because I didn't like the mounting method. I may modify my stock hangers as you have done.
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