just testing PDF on slideshare

1. Converting to Compression Pedal-Return Springs on
Act Labs Performance Pedals
...and never break a pedal spring again
Updated 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-lasting
compression springs in place of the poorly designed failure-prone springs in Act Labs
Performance 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 the
fabrication for the throttle spring. Unfortunately, I did not take the time to document the
process - this was originally a prototyping effort, and went through some changes from
concept to the final working stage. The final result isn't particularly well finished
aesthetically, but works very well for my purposes. In some photos below (without the
blue backgrounds), you can see the orignal prototype which only had a throttle pedal
modification. 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 neither
the hardest, easiest, quickest or best approach - it is merely the one which evolved as I
designed 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

2. Parts List
The Compression Spring
Assembly
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 quot;Old Stylequot; (2 springs per
pedal) Act Labs Performance Pedals (ALPP). This happened not long after I noticed many online references to
short the spring lives of the ALPP. Though replacement springs are available from Act Labs (for now) and the
replacement procedure isn't terrible (it's not a trivial process, however), my second spring breakage convinced
me to go through with fabricating this solution. The original Act Labs springs put all the pedal travel through
bending just two coils of wire - perhaps less than four inches of spring steel doing all the bending. My
converted 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, which
they refer to as quot;New Style.quot; They also have instructions for modifying the Old Style pedals for use with New
Style springs. However, my design still subjects the spring to far less fatigue over time, so I'm not inclined to
convert 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 with
less-than-perfect precision, partly due to limited tools, partly to lack of real training in the craft. However, I
typically 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 friend
who 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 list
at best.)
(2) compression springs, free length 7quot; long x 0.6875quot; (22/32quot; or 17.46mm) O.D. x 0.075quot; (1.9mm)
wire compression springs
Century Spring Corporation stock #2836 would probably be a good fit
Because I could only find springs at half this length, I used two 3.5quot; springs end-to-end for each
pedal, joined at the sliding collar half-way along the spring assembly. The spring rate from my

3. original prototype springs (0.041quot;/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 quot;Tquot; strap-tie (from an Orchard Supply Hardware
store) - used as a lower spring mount for both throttle and brake springs
(2) nylon bushings, 1quot; (25.4mm) long x 0.5quot; (12.7mm) O.D. x 0.33quot;+ (8.4mm) I.D. - serving to guide
the springs over the Bic™ pen tubes - also from OSH.
(2) Bic® Round Stic™ ball-point pens - for the outer guide tubes
(2) 6quot; (152.4mm) x 1/4quot; (6.35mm) bolts - used as sliding guide shafts for each pedal
these must have 5quot; or more of unthreaded shaft
(4) 1/4quot; nuts for the bolts above
be sure to match the thread pitch to the bolts
(2) 3/16quot; 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 3/16quot; pedal-end pivot bolt (next)
(1) 5/16quot; (7.94mm) x 7quot; (177.8mm) bolt - for lower pivot shaft
(5) 5/16quot; washers for bottom spring pivot (one on each side of spring eyes, one for nut)
(1) 5/16quot; nut - for lower spring pivot shaft
7quot; of tubing with at least 5/16quot; (8mm) I.D., used as spacer material between bottom spring bracket and
lower spring mounting eyes
(4-6) 1/4quot; (6.35mm) fender washers - used as spring seats
smallish - only have to have a greater diameter than the springs
5/16quot; I.D. tubing material to adjust spring preload (I used fuel hose)
1/2quot; (12.7mm) x 1/8quot; (3.175mm) mild steel bar stock - for the top yokes
(2) 2.5quot; (63.5mm) x 3/16quot; (4.76mm) bolt or rod stock (at least 2quot; of unthreaded shaft) - for pedal-end
pivot 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 springs
as throttle return springs in real cars, because if a tension spring breaks, a throttle stuck wide-open can be
very 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
quot;Round Sticquot; pen body tube as a guide tube for the 1/4quot; eye-bolt guide shaft. This is actually a pretty good
solution - 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, lower
underside of bottom spring bracket
mounts, and bracket

4. If you look at the photographs above, you can see the final assembly. It was tricky working out the appropriate
geometries and lengths for all the parts. The guide shaft has to travel the full stroke of the pedal without
quot;stackingquot; the spring, hitting the guide tube's end or the pedal base itself. The spring needs to have some quot;pre-
loadquot; at the full up position of the pedal, to provide some resistance and ensure that the throttle is completely
closed. The black cylinders visible between the washers at the bottom of the spring stacks are pieces of fuel
hose used to help preload the springs - without them, the throttle and brake pedals would sometimes fail to to
return to full top position.
The enormous holes cut in the black plastic base (below left) are cut as a relief for the spring/guide assembly
and the yoke. With more careful fabrication of the yoke, the holes could have been smaller.
detail of relief cut from base detail of quot;sliderquot;
In the middle of the spring (actually, where the two springs meet in the middle) is a 1quot; long nylon bushing. It's
inside diameter (I.D.) was originally 1/4quot;, but I drilled it out to a little over 5/16quot; to make a loose fit over the
the Bic pen tube. This slider (above and below) serves two purposes: it keeps the spring centered around the
guide tube, and prevents the end of the Bic pen tube from catching on the inside the spring coils as the throttle
pedal moves (inside the throttle spring, there's also an additional cardboard cylinder to accomodate the larger
throttle springs). If you compare the quot;compression spring assembliesquot; photo above (click it to see an larger
view) and the quot;full throttlequot; images below, you can see that this slider (anchored to the spring by nylon wire
ties) moves from the top end of the Bic tube at full-closed throttle to about half-way down at full open
throttle. At the top end of the spring, the 1/4quot; nut which jams the shaft to the top yoke also serves to keep the
spring centered.
assembly at full throttle (prototype) detail of top link at full throttle (prototype)

5. The top yoke was fabricated from some 1quot; x 1/8quot; steel bar stock I had around. The yoke must not physically
interfere with the pedal face, pedal arm or the case for its entire travel. The guide shaft is made from a 1/4quot;
bolt (it has 6quot; of unthreaded rod, I don't recall the stated length). At the yoke end, a 1/4quot; nut is first threaded
all the way to the end of the threads (and retained by a thread-locking compound), then the yoke is clamped
against this first nut by a second nut. The lower end of the guide shaft is where the bolt hex head was
originally - the bolt head has been cut off and the end rounded and smoothed to slide back and forth within
the pen tube with no resistance. When the pedal is at it's highest point, there needs to be adequate guide shaft
within the guide tube to serve as a suitable guide - I think I've got from 1quot; to 1.25quot;. The excess thread length at
the yoke end was cut off to prevent interference with the pedal. The shape of the yoke proved tricky, as I was
determined to keep its entire 1quot; width for strength. When I later crafted the brake pedal yoke (see quot;detail of
brake pedal yoke...quot; below), I made a much leaner yoke after realizing that the throttle yoke was unnecessarily
robust. 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 quot;detail of lower spring mounting eyequot;
below) to serve as a lower spring mounting eye. Because this joint is under compression, glue adhesion isn't
a significant issue, it's mostly to keep it wobble-free and hold the bits together during assembly. Small fender
washers 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 3/16quot; bolt is inserted through an existing molded lateral tube through the pedal arm
as a top pivot pin.
For the bottom spring bracket, I found a galvanized steel quot;strap-tiequot; (used to augment lumber joints in
construction) in the hardware store and decided to design around it. This virtually eliminated cutting (except
for 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). Two
holes drilled into the upturned quot;wingsquot; of the steel serve to locate an 8quot; long, 5/16quot; bolt, which serves as a
common lower pivot shaft for throttle and brake springs. Some plastic pipe I had around serves as spacer
material to precisely position the bottom pivots of both pedal springs. In the quot;lower pivot shaft detailquot; image
below right, you can see the shiny black plastic tubing is cut into four pieces: two very short pieces between
the lower spring mounting eyes and the quot;Tquot;-shaped steel bracket; a long piece between the two mounting
eyes; and another long piece to compensate for the fact that the bolt was too long.

6. 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, where
pressure against the driver's foot must substitute for real-world acceleration cues on the driver's body and inner
ear. 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 harnesses
so that I can substitute the Logitech pedals with Act Labs Performance Pedals (ALPP). This allows the
use of the superior ALPP with games and sims which do not support multiple game controllers, and
eliminates the redundant Logitech pedals under the desk.
I've posted a page with my fabrication of replacement steel shift paddles for the Logitech Wingman
Formula Force wheel. Along with a pair of microswitches, this modification should eliminate future
failure of the original switches and paddles themselves.
Jens Schumacher has designed and machined a clever kit to replace the Logitech Wingman Formula
Force'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 really
want to feel the hard work sim programmers have put into force-feedback, it's a must-have. You can
buy the kit (Jens has graciously made these available to serious enthusiasts at his cost) by contacting him
at his Logi-corner website.
Contact
If you have a question specific to this project, you can email me at (you'll have to
type 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