Converting to Compression Pedal-Return Springs onAct Labs Performance Pedals

...and never break a pedal spring againUpdated 4/26/05 - Dual-Pedal Spring Modification!Now with accelerator and brake pedal springs

This page contains some images and notes of a modification I made to utilize long-lastingcompression springs in place of the poorly designed failure-prone springs in Act LabsPerformance Pedals. (As of some time in 2004, Act Labs no longer sells this product.)

This is not a set of instructions, but a loose photojournal of the final results of thefabrication for the throttle spring. Unfortunately, I did not take the time to document theprocess - this was originally a prototyping effort, and went through some changes fromconcept to the final working stage. The final result isn't particularly well finishedaesthetically, but works very well for my purposes. In some photos below (without theblue backgrounds), you can see the orignal prototype which only had a throttle pedalmodification. The final version features modified throttle and brake springs.

If you decide to undertake this task, it can be accomplished in many ways. This is neitherthe hardest, easiest, quickest or best approach - it is merely the one which evolved as Idesigned it. Hopefully, this will inspire you to engineer a similar mod to your own pedals.Best of luck. - Ellsworth

(click on any images on this page for larger image)

Contents

Why Replace the Springs?

Can You Do This?

Parts List

Parts List

The Compression SpringAssembly

Results

More Info/Contact

The Final Compression Spring Mod

Why replace the springs?

My original throttle spring broke after perhaps 6 months of intermittent use of my "Old Style" (2 springs perpedal) Act Labs Performance Pedals (ALPP). This happened not long after I noticed many online references toshort the spring lives of the ALPP. Though replacement springs are available from Act Labs (for now) and thereplacement procedure isn't terrible (it's not a trivial process, however), my second spring breakage convincedme to go through with fabricating this solution. The original Act Labs springs put all the pedal travel throughbending just two coils of wire - perhaps less than four inches of spring steel doing all the bending. Myconverted spring uses at least 14 coils - putting all those throttle cycles through over two feet of spring steel.Fatigue-based failure should be eliminated.

(6/1/04: I just discovered that Act Labs now makes the Performance Pedals with a single spring design, whichthey refer to as "New Style." They also have instructions for modifying the Old Style pedals for use with NewStyle springs. However, my design still subjects the spring to far less fatigue over time, so I'm not inclined toconvert back to their system at this point.)

Can you do this yourself?

This was accomplished primarily with common hand and power tools. I'm not a professional metal-worker,but have done quite a bit of fabrication for small personal projects. I don't have a proper metal-working shop,and lack many useful large tools (band saw, drill press). On many projects, including this one, I end up withless-than-perfect precision, partly due to limited tools, partly to lack of real training in the craft. However, Itypically allow for this in my long planning process.

If you're handy with working metal, you might be able to accomplish this. If not, perhaps you have a friendwho can help.

Parts List (not comprehensive)

(I'm documenting this some time after construction, and I did not take notes at the time, so this is a rough listat best.)

(2) compression springs, free length 7" long x 0.6875" (22/32" or 17.46mm) O.D. x 0.075" (1.9mm)wire compression springs

Century Spring Corporation stock #2836 would probably be a good fitBecause I could only find springs at half this length, I used two 3.5" springs end-to-end for eachpedal, joined at the sliding collar half-way along the spring assembly. The spring rate from my

original prototype springs (0.041"/1.04mm wire) is probably similar to the stock ALPP springing.My final design uses much heavier springs - even heavier for the throttle.

(1) Simpson Strong-Tie® #1212T galvanized steel "T" strap-tie (from an Orchard Supply Hardwarestore) - used as a lower spring mount for both throttle and brake springs(2) nylon bushings, 1" (25.4mm) long x 0.5" (12.7mm) O.D. x 0.33"+ (8.4mm) I.D. - serving to guidethe springs over the Bic™ pen tubes - also from OSH.(2) Bic® Round Stic™ ball-point pens - for the outer guide tubes(2) 6" (152.4mm) x 1/4" (6.35mm) bolts - used as sliding guide shafts for each pedal

these must have 5" or more of unthreaded shaft(4) 1/4" nuts for the bolts above

be sure to match the thread pitch to the bolts(2) 3/16" eye screws or eye bolts - these serve as lower spring mounting eyes

with an interior diameter of the eye which is an easy fit for the 3/16" pedal-end pivot bolt (next)(1) 5/16" (7.94mm) x 7" (177.8mm) bolt - for lower pivot shaft

(5) 5/16" washers for bottom spring pivot (one on each side of spring eyes, one for nut)(1) 5/16" nut - for lower spring pivot shaft

7" of tubing with at least 5/16" (8mm) I.D., used as spacer material between bottom spring bracket andlower spring mounting eyes(4-6) 1/4" (6.35mm) fender washers - used as spring seats

smallish - only have to have a greater diameter than the springs5/16" I.D. tubing material to adjust spring preload (I used fuel hose)1/2" (12.7mm) x 1/8" (3.175mm) mild steel bar stock - for the top yokes(2) 2.5" (63.5mm) x 3/16" (4.76mm) bolt or rod stock (at least 2" of unthreaded shaft) - for pedal-endpivot pins

nuts and washers for above

The Compression Spring Assembly (click on any image to enlarge)

Using a long compression spring requires some method for guiding the spring (I've used compression springsas throttle return springs in real cars, because if a tension spring breaks, a throttle stuck wide-open can bevery exciting). I chose to internally guide the spring (as opposed to encasing the spring in tubes, like a toilet-paper spindle). After much experimenting and measuring of available materials, I ended up using a Bic"Round Stic" pen body tube as a guide tube for the 1/4" eye-bolt guide shaft. This is actually a pretty goodsolution - just enough stiffness to keep the spring aligned, and a nice natural lubricity that keeps the steel eye-bolt shaft quietly sliding.

compression spring assemblies, lowermounts, and bracket

underside of bottom spring bracket

If you look at the photographs above, you can see the final assembly. It was tricky working out the appropriategeometries and lengths for all the parts. The guide shaft has to travel the full stroke of the pedal without"stacking" the spring, hitting the guide tube's end or the pedal base itself. The spring needs to have some "pre-load" at the full up position of the pedal, to provide some resistance and ensure that the throttle is completelyclosed. The black cylinders visible between the washers at the bottom of the spring stacks are pieces of fuelhose used to help preload the springs - without them, the throttle and brake pedals would sometimes fail to toreturn to full top position.

The enormous holes cut in the black plastic base (below left) are cut as a relief for the spring/guide assemblyand the yoke. With more careful fabrication of the yoke, the holes could have been smaller.

detail of relief cut from base detail of "slider"

In the middle of the spring (actually, where the two springs meet in the middle) is a 1" long nylon bushing. It'sinside diameter (I.D.) was originally 1/4", but I drilled it out to a little over 5/16" to make a loose fit over thethe Bic pen tube. This slider (above and below) serves two purposes: it keeps the spring centered around theguide tube, and prevents the end of the Bic pen tube from catching on the inside the spring coils as the throttlepedal moves (inside the throttle spring, there's also an additional cardboard cylinder to accomodate the largerthrottle springs). If you compare the "compression spring assemblies" photo above (click it to see an largerview) and the "full throttle" images below, you can see that this slider (anchored to the spring by nylon wireties) moves from the top end of the Bic tube at full-closed throttle to about half-way down at full openthrottle. At the top end of the spring, the 1/4" nut which jams the shaft to the top yoke also serves to keep thespring centered.

assembly at full throttle (prototype) detail of top link at full throttle (prototype)

The top yoke was fabricated from some 1" x 1/8" steel bar stock I had around. The yoke must not physicallyinterfere with the pedal face, pedal arm or the case for its entire travel. The guide shaft is made from a 1/4"bolt (it has 6" of unthreaded rod, I don't recall the stated length). At the yoke end, a 1/4" nut is first threadedall the way to the end of the threads (and retained by a thread-locking compound), then the yoke is clampedagainst this first nut by a second nut. The lower end of the guide shaft is where the bolt hex head wasoriginally - the bolt head has been cut off and the end rounded and smoothed to slide back and forth withinthe pen tube with no resistance. When the pedal is at it's highest point, there needs to be adequate guide shaftwithin the guide tube to serve as a suitable guide - I think I've got from 1" to 1.25". The excess thread length atthe yoke end was cut off to prevent interference with the pedal. The shape of the yoke proved tricky, as I wasdetermined to keep its entire 1" width for strength. When I later crafted the brake pedal yoke (see "detail ofbrake pedal yoke..." below), I made a much leaner yoke after realizing that the throttle yoke was unnecessarilyrobust. The throttle would have been fine with the lighter brake yoke design.

A screw eye is glued into the end of each guide tube using epoxy (see "detail of lower spring mounting eye"below) to serve as a lower spring mounting eye. Because this joint is under compression, glue adhesion isn'ta significant issue, it's mostly to keep it wobble-free and hold the bits together during assembly. Small fenderwashers serve as spring seats so the springs have a square surface to bear their loads.

detail of brake pedal yoke and pivot pin detail of lower spring mounting eye

In the image above left, a 3/16" bolt is inserted through an existing molded lateral tube through the pedal armas a top pivot pin.

For the bottom spring bracket, I found a galvanized steel "strap-tie" (used to augment lumber joints inconstruction) in the hardware store and decided to design around it. This virtually eliminated cutting (exceptfor a small notch cut as a relief for a service port in the bottom of the ALPP) and required only two right-angle bends. The spring mount is pop-riveted to the bottom of the pedal base (see photo, below left). Twoholes drilled into the upturned "wings" of the steel serve to locate an 8" long, 5/16" bolt, which serves as acommon lower pivot shaft for throttle and brake springs. Some plastic pipe I had around serves as spacermaterial to precisely position the bottom pivots of both pedal springs. In the "lower pivot shaft detail" imagebelow right, you can see the shiny black plastic tubing is cut into four pieces: two very short pieces betweenthe lower spring mounting eyes and the "T"-shaped steel bracket; a long piece between the two mountingeyes; and another long piece to compensate for the fact that the bolt was too long.

bottom spring bracket attachment detail lower pivot shaft detail

Results

The final result works perfectly. The increased spring stiffness is just what I want for sim driving, wherepressure against the driver's foot must substitute for real-world acceleration cues on the driver's body and innerear. Together with the Act Labs pedals' longer travel, this is exactly what I want in sim pedals.

I'm extremely pleased that I'll no longer have to concern myself with broken springs.

More Info

I've documented in great detail modifying one of my Logitech Wingman Formula Force pedal harnessesso that I can substitute the Logitech pedals with Act Labs Performance Pedals (ALPP). This allows theuse of the superior ALPP with games and sims which do not support multiple game controllers, andeliminates the redundant Logitech pedals under the desk.I've posted a page with my fabrication of replacement steel shift paddles for the Logitech WingmanFormula Force wheel. Along with a pair of microswitches, this modification should eliminate futurefailure of the original switches and paddles themselves.Jens Schumacher has designed and machined a clever kit to replace the Logitech Wingman FormulaForce's original nylon and plastic bearings and bushings with precision ball bearings and brass bushings.It's not an easy task to install the kit (easier than fabricating the paddles above, though), but if you reallywant to feel the hard work sim programmers have put into force-feedback, it's a must-have. You canbuy the kit (Jens has graciously made these available to serious enthusiasts at his cost) by contacting himat his Logi-corner website.

Contact

If you have a question specific to this project, you can email me at (you'll have totype in this email address by hand).If you discover or create a solution that might help others, please contribute it to others on the Web.That's what it's for.

All contents Copyright 2004 Ellsworth Chou