Balance bar pedal box

[gav]

Morning all
For those who are allowed to run a twin master cylinder pedal box, does it bolt directly onto the grp.
If so, do you reinforce the grp? I am thinking about adding some aluminium honeycomb between the pedal box and grp both horizontally and on the vertical bulkhead behind the pedals.
Is this the way to go?
Thanks
Gavin

[Elan45]

Gavin,

I've often wondered the same question. Compounding my concerns is that my S3/26R is LHD. The original owner of that car was a medical doctor and I believe his conversion to 26R that happened 45 years ago was done by another shop and not all parts were available, especially not a LHD pedal box for balance bar.

So, the adjoining brake MC clevises are simply bolted through the original brake pedal. I will probably have to fabricate a LHD pedal box myself and if so, will use the balance bar pieces from a Lotus 22-23. The doctor passed on in the early 70's and his son crashed it over the winter of 1974-75. I bought it 10 years later still broken, but with all the 26R potential. I can still remember driving up the street where it had been taken, seeing and recognizing the 26R wheels from a distance and trying to hide my excitement.

Unfortunately, it has sat again as purchased, since other Lotus projects and racing took precedence.

Roger

[bill308]

Both Kelvedon and TTR offer balance bar systems, that mount quite differently.

The Kelsport assembly appears to attach to both the upper horizontal surface of the pedal box and the front vertical surface. If this is true, some additional layers of glass/resin might be appropriate on these surfaces. Posted cost: 541.42 GBP. See

http://www.kelsport.net/parts/product_d ... ectionID=2

The TTR assembly appears to attach to the front vertical surface only. It is however, much wider and taller than the Kelsport assembly, so should attach near the intersection of the connecting walls, a relatively stiff area. Some localized reinforcement might be appropriate. Posted cost: 550.00 GBP. See

http://shop.tonythompsonracing.co.uk/tt ... -215-p.asp

Anybody have experience with either of these systems?

Bill

[toomspj]

For a lightweight shell I believe it is prudent to reinforce the bulkhead where the pedals attach - I used sheet aluminium for mine so that i could form it around the folds in the body. I don't believe that you need to reinforce the upper surface of the footwell as very little load is transmitted to it.

For a roadcar shell i think you need to make sure the condition of the fibreglass is good (or make it good). The fibreglass is really quite thick so in my opinion you don't need to add extra reinforcement.

The Pat Thomas (Kelvedon Lotus) one comes with a steel plate that fits the other side of the bulkhead from the pedals providing additional reinforcement.

Paul

[Panda]

I fitted the Kelsport version to my racing Elan about 2 years ago without any additional reinforcement. It is well made, and as Paul mentions, it comes with reinforcement on the engine side.
There is no problem with flexing of the bulkhead and it is, with care, easy to fit. I did look into the TTR pedal set and was sent fitting instructions. As the pedals hinged at the bottom, I felt it was going away from originality, and the fitment looked difficult.
cheers

Alan P

[gav]

Thanks all for the input and particularly Bill who has helped identify the pedal boxes.

Alan - although the TTR unit was originally a floor based unit, they do say that it can be hung as well but having researched it further, whilst it appears much lighter than the Kelvedon unit, it does look a little complicated to fit.

Having now removed my original pedals, I think I will reinforce the bulkhead with some honeycomb internally and ally sheet in the engine bay. The area does look rather tired and with the additional loads being placed in the area I'd rather be safe.

Cheers
Gavin

[gav]

What a saga - well it is fitted now and it certainly isn't coming out again - well not in a hurry anyway.
I reinforced the bulkhead as planned, cut out a small chunk of the wheel arch to cleat the extra master, glassed up a new shape and am now just finishing the reservoir plumbing.
The set is very adjustable but was very tricky to fit and I reckon I had around 25 dry runs before everything was finally installed.
The orientation of the pedal box doesn't seem to matter and I found an alternative supplier - Trident Racing Supplies who were really helpful with spares. Whilst the box weighs 2 1/2 kilos, the entire set up probably weighs a lot more with the extra glass and reinforcement I introduced. The final solution is very neat though. All this for an extra master cylinder.
I'll let you know how it feels once the system is bled and set up.
All good fun
Gavin

[bill308]

Hi Gavin.

I looked at the Trident Racing catalog and they show the same pedal box (575 GBP) as offered by TTR (550 GBP). Is this the one you installed?

What diameter master cylinders are you using for the brakes and clutch?

I'm about to purchase the Kelsport version with wing (fender) cavity reservoirs. This looks like a cleaner/easier installation. There should be no reason to reinforce the fiberglass foot well box because the Kelsport assembly appears to attach to both the upper horizontal panel and forward vertical panel of the foot box. The horizontal panel should react most of the pedal push (fore-aft) loads and the vertical panel should react all vertical (up-down) loads. Both panels will effectively react all left-right loads. The only load not efficiently dealt with by geometry is a moment that will want to rotate the assembly backward toward the top, or if viewed from the port (left) side of the car, the pedal box rotation will want to be clockwise.

Bill

Bill

[gav]

Hi Bill

The Trident box bolts both vertically and horizontally so in that respect I think they are similar in principle. The problem for me was that my bulkhead moulding isn't square so I ended up reinforcing and packing at the same time.
I was lucky and bought the pedal box from ebay at a fraction of the price so I decided to persevere with it.

I have seen the Kelsport kit - it looks good but is much heavier in comparison being based on steel rather than aluminium.

My brake set up is very unusual - I am using a Spyder RSC rear upright and I got them to fix brackets for a Sierra caliper so that I could have a handbrake that is reliable. What I hadn't realised is that it is much more powerful than the front caliper so it created a significant imbalance that caused me to spin.

The front brakes are Caterham four pots on vented discs (the Caterham set up bolted straight on).
I am runnning a 0.6 master for the front and a 0.75 for the rears. I also have a lever pressure regulator on the tunnel to fine tune the rears.

I use AP racing masters because they are really finely engineered and have no slop in the travel to take up. My AP man is very helpful and suggested that I should use the lever to adjust the pressure rather than the balance bar because it is hard to work out where the balance is and reading the words, it only has a 15% impact which is probably too subtle for me to notice (my view not his). I set the balance centrally and will lock the balance bar to stop it creeping.

In terms of bracketry, I also got hold of a long 7mm ally angle and linked it to the vertical bulkhead (behind the dash) and the top mountings of the pedal box to add strength to the front-rear plane. Probably overkill but that's me..

Hope this helps

Good luck Gavin

[bill308]

Hi Gavin.

Thanks for the info.

I've been struggling a bit on what diameter master cylinders (MC's) to choose. One way to control brake balance (front to rear) is by selecting particular diameter MC's. The three that Kelsport offer are 0.625, 0.70, and 0.75 inch diameters. Starting with the smallest, 0.625 inches, the 0.70 and 0.75 inch diameters result in effective area increases of 25% and 15% respectively, above their next smaller option. Any increase in area means a corresponding decrease in line pressure, all else being the same. What this means is if you need more adjustment than what the balance bar can provide (15% or +/-7.5%) when fitted with identical master cylinders (say 2-cylinders each with a 0.625 inch bore), one can change one or more of the master cylinders to adjust the range or balance. The other thing to look out for is that the volume displacement of the master cylinder is sufficient to take up the brake piston gap and provide sufficient grip range yet still provide an acceptable line pressure.

My S2 was fitted with a single brake master cylinder havening a diameter of 0.70 inches. S3/S4 and Sprint used a 0.70 inch tandem MC. When changing to a two master cylinder setup, the sum of the new areas ought to be equivalent to the single cylinder for the same pedal force, again, all else assumed the same. But is all else the same? The big unknown in my mind is the pedal lever geometry. Without knowing this geometry one can't select the appropriate MC's with confidence. Kelsport have recommended selecting MC's of the same size as originally fitted. I'm thinking the smallest 0.625 inch diameter MC's to start with for a little more line pressure along with +2 (16PB, 2.12 inch diameter pistons) front calipers and standard (1.34 inch diameter) rear calipers.

Bill

[gav]

Bill
Sorry - made a mistake, I am using a .625 on the fronts.

When the brakes were on one circuit I started using a .7 but the pedal was wooden in feel so I changed to a .625 with the pressure reducer on the rear.

I have just bled the new masters and the pedal is really firm so hopefully the pedal will feel ok - I don't fancy changing them again

I hope this helps.

All the best
Gavin