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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PostPost by: 1owner69Elan » Tue Aug 21, 2018 8:33 pm

I installed the (Kelvedon) 1" tubular anti roll bar (ARB) today. Relatively easy, especially with the adjustable drop links. I did have some work to get the poly bushes inserted into the upper part of the links but finally got them in. The ARB did come with standard rubber type bushings but I pressed those out and installed poly instead. (Thinking I'd like these to last for the duration).

The bar obviously looks substantially fatter, but remember it is tubular(hollow) so effectively less stiff than a solid bar of the same OD. It is about 2.3x the stiffness of the stock ARB (11/16" solid) while being 1.6 pounds lighter (including drop links). About 10% less stiff than a 7/8" (22mm) solid bar (but ~5 lbs lighter!).

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I only have taken a short test run with the new ARB. General impression is that there is certainly less body roll. In the limit, one starts to feel understeer. Is the car faster in the corners? Probably, but no objective way to know as I don't have scientific timings.

I can say that I can fling the car, at speed, into relatively sharp corners and fast transition S-curves, with some abandon, and without experiencing any loss of balance or control. In the limit, as I said, one can feel an understeer start as the front end starts to feel light. But, this is a street car, not a racer, so I won't (shouldn't) be at the limit very often.

Couple of things I can readily do to further fine tune:

1. Tire pressures. I was running 23/28 psi cold on the Toyo R888R 185/60r13's. The spec for a "very light" car (<800kgs) is given as 17 to 22 psi.

2. Increase (add) spacers to bring the rear "bump stops" into engagement earlier. These are not the original Aeon springs but rather harder (still progressive) material - currently cut down to original Aeon length. Rohan has indicated a 20mm spacer is appropriate. Right now I have only about a 3mm spacer. So, a lot of room to play with. I'm using stackable "strut packers" so no need to disassemble the spring/strut unit to fit. Bringing the "bump stops (progressive springs)" into play earlier would presumably provide some reduction in the perceived understeer.


BTW: My test track is a long private road to my house (~2 miles). Fortunate to have this. No issues with the authorities being offended by my behavior. Just need to avoid the vineyard management vehicles
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PostPost by: Davidb » Tue Aug 21, 2018 10:04 pm

We approve of your test track and wonder when the group test day will be? 8)
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PostPost by: SENC » Wed Aug 22, 2018 1:18 am

Davidb wrote:We approve of your test track and wonder when the group test day will be? 8)

Indeed!
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PostPost by: rgh0 » Wed Aug 22, 2018 11:24 am

I would try running around 27 PSI both front and rear to reduce front under-steer a little

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PostPost by: 1owner69Elan » Mon Sep 03, 2018 10:28 pm

I had to stop testing my new anti roll (sway) bar for a bit due to a front wheel bearing failure. I had just adjusted tire pressures as per Rohan's suggestion when I started to hear some noise from the front. Initial investigation, indicated that left front wheel bearing(s) had gone. Tearing it down, I discovered that the outer bearing race had shifted inward in the 26r alloy hub causing a loose condition on the bearing/hub. Apparently, this bearing movement was caused by my spirited ("racing type") test driving.

I have 26r alloy hubs and had simply pressed the bearings in, interference fit, with no bearing cement. As noted elsewhere on the Forum these alloy hubs can apparently be problematic.

Fortunately, there was no great damage, but the D washer (large one) was rubbing on the inside of the hub because of looseness and creating the noise. The D washer showed some distortion caused by rubbing on the inside of the hub. The new D washer that has been fitted is of a smaller diameter than my original (from standard k/o hubs) that I had fitted (after it had been ground down to be a bit smaller to fit inside the 26r hubs). A couple of my usual suppliers (TTR and Bean) don't bother to differentiate between k/o or bolt-on D washers and only now supply the smaller bolt-on one for all occasions. Anyway, that is perhaps another whole other line of discussion.

So with the bearing race now cemented in place, replacing the bearing and D washer, and the front suspension reassembled, I have now been able to resume testing of the effect of the new ARB. The modified tire pressures as per Rohan seem to have subtly improved the slight understeer. In fact, the car seems quite neutral and balanced throughout various turns at the speeds that my nerve will allow. I haven't been able to push the car past its limits, but I remind myself this is intended as a road car.

With the larger ARB there is substantially less body lean. The car is very controllable with no nasty behaviors. So, my conclusion is that going to the larger 1" tubular swaybar (almost equivalent stiffness to a 7/8" solid, per Rohan's recommendation) has been a nice improvement. The ARB modification coupled with the wide/sticky tires, stiffer fast road springs, adjustable spring perches, longer rear "bump" (rubber spring) stops, poly bushes throughout, solid steering mounts, heavy duty diff/trans mounts, Quaife ATB, CV conversion, etc..., provides an overall balanced equation of suspension/handling/power transmission commensurate with the uprated engine output. i may continue to fine tune matters but I think I have gotten close to where I want to be.
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PostPost by: Davidb » Mon Sep 03, 2018 11:57 pm

Interesting! I have the aluminium front 26R hubs and I have had no problem-this after off road use last year and this--I specifically checked the front wheel bearings for play before and after last weekends 1000 mile jaunt which included hours of off-road use that is hard on wheel bearings.

When I raced a 26R in the eighties-with the original aluminium/bronze hubs-I had a problem with the outer races coming loose in the hubs.
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