pedal design -- ideas for increasing resolution

Suggestions/input/ideas wanted: As a personal project I want to design a set of pedals that will give a high and fine degree of control (yeah... buy some high-end pedals -- but I like to build stuff, ok?). On examination of the pedal internals I have personally seen (not many) it seems to me that depressing the brake/throttle only results in the pot turning a small percentage of its potential, a basic 1:1 movement. I am thinking that a simple gear reduction box may translate a pedal throw of a few inches into a pot revolution somewhere between 180 and 270 degrees. I am not an engineer, but it seems to me that this would result in a finer degree of control, especially throttle control. In fact, if I recall correctly, wasnt the old T2 pedal unit based on this design? Do any of the current mass market and/or high-end pedals use a similar design? Anyway, any input from this group would be useful.

From our testing on our pedal design the pot movement isn't really that critical. The Momo pedals for example only move the pot about 15 degrees and yet it is as sensitive as ones moving 3-4 times that. In our design and a few others that are similar the movement is anywhere from 45-1120 degrees. I don't think you will gain anything with more pot travel. "Bruce Millar" <[email hidden]> wrote in message news:[email hidden]...

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> Suggestions/input/ideas wanted: As a personal project I want to > design a set of pedals that will give a high and fine degree of > control (yeah... buy some high-end pedals -- but I like to build > stuff, ok?). On examination of the pedal internals I have personally > seen (not many) it seems to me that depressing the brake/throttle only > results in the pot turning a small percentage of its potential, a > basic 1:1 movement. I am thinking that a simple gear reduction box > may translate a pedal throw of a few inches into a pot revolution > somewhere between 180 and 270 degrees. I am not an engineer, but it > seems to me that this would result in a finer degree of control, > especially throttle control. In fact, if I recall correctly, wasnt > the old T2 pedal unit based on this design? Do any of the current > mass market and/or high-end pedals use a similar design? Anyway, any > input from this group would be useful.

The BRD Pro pedals use this method, and from my experience you gain more precision and less jitter. Whether this translates into more effective pedal control is perhaps open to debate. When BRD bring out their driver to allow the pedal response to be tuned this extra precision may be well worth having. An additional advantage tho is that using a larger range of movement in the pot significantly increases its lifetime (according to BRD) whch makes a lot of sense to me. Paul "Schooner" <[email hidden]> wrote in message news:rikf9.66817$[email hidden]...

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> From our testing on our pedal design the pot movement isn't really that > critical. The Momo pedals for example only move the pot about 15 degrees > and yet it is as sensitive as ones moving 3-4 times that. > In our design and a few others that are similar the movement is anywhere > from 45-1120 degrees. > I don't think you will gain anything with more pot travel. > > "Bruce Millar" <[email hidden]> wrote in message > news:[email hidden]... > > Suggestions/input/ideas wanted: As a personal project I want to > > design a set of pedals that will give a high and fine degree of > > control (yeah... buy some high-end pedals -- but I like to build > > stuff, ok?). On examination of the pedal internals I have personally > > seen (not many) it seems to me that depressing the brake/throttle only > > results in the pot turning a small percentage of its potential, a > > basic 1:1 movement. I am thinking that a simple gear reduction box > > may translate a pedal throw of a few inches into a pot revolution > > somewhere between 180 and 270 degrees. I am not an engineer, but it > > seems to me that this would result in a finer degree of control, > > especially throttle control. In fact, if I recall correctly, wasnt > > the old T2 pedal unit based on this design? Do any of the current > > mass market and/or high-end pedals use a similar design? Anyway, any > > input from this group would be useful. > >

Yes, your wearing over a larger area of the pot so it should wear more evenly and last a bit longer. "Paul Harrington" <[email hidden]> wrote in message news:yclf9.808$aB3.36688@newsfep2-gui... > The BRD Pro pedals use this method, and from my experience you gain more > precision and less jitter. Whether this translates into more effectivepedal > control is perhaps open to debate. When BRD bring out their driver toallow > the pedal response to be tuned this extra precision may be well worth > having. > > An additional advantage tho is that using a larger range of movement inthe > pot significantly increases its lifetime (according to BRD) whch makes alot

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> of sense to me. > > Paul > > "Schooner" <[email hidden]> wrote in message > news:rikf9.66817$[email hidden]... > > From our testing on our pedal design the pot movement isn't really that > > critical. The Momo pedals for example only move the pot about 15

degrees

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> > and yet it is as sensitive as ones moving 3-4 times that. > > In our design and a few others that are similar the movement is anywhere > > from 45-1120 degrees. > > I don't think you will gain anything with more pot travel. > > > > "Bruce Millar" <[email hidden]> wrote in message > > news:[email hidden]... > > > Suggestions/input/ideas wanted: As a personal project I want to > > > design a set of pedals that will give a high and fine degree of > > > control (yeah... buy some high-end pedals -- but I like to build > > > stuff, ok?). On examination of the pedal internals I have personally > > > seen (not many) it seems to me that depressing the brake/throttle only > > > results in the pot turning a small percentage of its potential, a > > > basic 1:1 movement. I am thinking that a simple gear reduction box > > > may translate a pedal throw of a few inches into a pot revolution > > > somewhere between 180 and 270 degrees. I am not an engineer, but it > > > seems to me that this would result in a finer degree of control, > > > especially throttle control. In fact, if I recall correctly, wasnt > > > the old T2 pedal unit based on this design? Do any of the current > > > mass market and/or high-end pedals use a similar design? Anyway, any > > > input from this group would be useful. > > > > > >

Bruce Millar <[email hidden]> wrote in message news:[email hidden]...

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> basic 1:1 movement. I am thinking that a simple gear reduction box > may translate a pedal throw of a few inches into a pot revolution > somewhere between 180 and 270 degrees. I am not an engineer, but it > seems to me that this would result in a finer degree of control, > especially throttle control. In fact, if I recall correctly, wasnt > the old T2 pedal unit based on this design? Do any of the current > mass market and/or high-end pedals use a similar design? Anyway, any > input from this group would be useful.

Interact V3 pedals use a rack (or possibly a small arc of a very big gear ;-) on the pedals to drive a small gear on the pot spindle. Works nicely, although my original throttle pot still wore out around my usual 'feathering point' in GPL! Jonny

The pots turn very few degrees, but they are not normal pots, and they rotate near their full range. If you wan't to build something high end, use a digital encoder of some kind. If you have to build something that adapts to an existing wheel or to a game port, connect it to a digital pot. If you place the digital pot near the wheel/gameport, you will make it more imune to noise. No more worn pots! Jone.

I would disassemble a hi-resolution mice (like those gaming-mices) and use the optical reader of those in the wheel. That should be pretty good ok (atleast for no wornout pots :) "Bruce Millar" <[email hidden]> wrote in message news:[email hidden]...

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> Suggestions/input/ideas wanted: As a personal project I want to > design a set of pedals that will give a high and fine degree of > control (yeah... buy some high-end pedals -- but I like to build > stuff, ok?). On examination of the pedal internals I have personally > seen (not many) it seems to me that depressing the brake/throttle only > results in the pot turning a small percentage of its potential, a > basic 1:1 movement. I am thinking that a simple gear reduction box > may translate a pedal throw of a few inches into a pot revolution > somewhere between 180 and 270 degrees. I am not an engineer, but it > seems to me that this would result in a finer degree of control, > especially throttle control. In fact, if I recall correctly, wasnt > the old T2 pedal unit based on this design? Do any of the current > mass market and/or high-end pedals use a similar design? Anyway, any > input from this group would be useful.

Here are some pictures of some pedals I built. They use a rack and get close to full pot potation. The pedals are actually a bit more refined now than when I took the pictures but they may give you some ideas. Someday I will get around to updating this site. http://home.maine.rr.com/spark/ped_main.htm Spark

Gears could work, but if you are not careful to use very low lash gears you will actually be adding some imprecision. Gears don't really drive at a constant ratio unless there is zero lash, it's more like start - stop - catch up - start again with each tooth. But with zero lash they tend to bind up easily and not live very long. A small cogged belt would probably give you better results. I have seen those used in instrument control systems, so I believe they can be very precise. "Bruce Millar" <[email hidden]> wrote in message news:[email hidden]...

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> Suggestions/input/ideas wanted: As a personal project I want to > design a set of pedals that will give a high and fine degree of > control (yeah... buy some high-end pedals -- but I like to build > stuff, ok?). On examination of the pedal internals I have personally > seen (not many) it seems to me that depressing the brake/throttle only > results in the pot turning a small percentage of its potential, a > basic 1:1 movement. I am thinking that a simple gear reduction box > may translate a pedal throw of a few inches into a pot revolution > somewhere between 180 and 270 degrees. I am not an engineer, but it > seems to me that this would result in a finer degree of control, > especially throttle control. In fact, if I recall correctly, wasnt > the old T2 pedal unit based on this design? Do any of the current > mass market and/or high-end pedals use a similar design? Anyway, any > input from this group would be useful.

I found that I get about 150 degrees of rotation, very smooth. I have built 4 complete sets of the controllers in the link below. http://kbrl.com/controllers_kbr.htm Jeff "Haqsau" <[email hidden]> wrote in message news:allqit$1r5dqm$[email hidden]...

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> Gears could work, but if you are not careful to use very low lash gears > you will actually be adding some imprecision. Gears don't really drive > at a constant ratio unless there is zero lash, it's more like start - > stop - catch up - start again with each tooth. But with zero lash they > tend to bind up easily and not live very long. A small cogged belt > would probably give you better results. I have seen those used in > instrument control systems, so I believe they can be very precise. >

I agree with the other posters about using digital over analog, but if analog, then consider carefully the electrical component choice, namely the range of resistance of the pot. Some values can result in better precision. There was some discussion of this in connection with the PDP4 card, try doing some google searches or look on joystick websites. rms [email hidden]

Spark, very nice. I am wondering what the purpose of the cam under your brake pedal, in front of the shock absorber is? Did you put that there to change the direction of movement so the shock could be placed under the platform to save space, or is there another reason? Also, is the shock an auto part (hood/trunk shock) -- I was under the impression that those hood shocks were too stiff to be used for this application, but you are obviously using one.

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> Here are some pictures of some pedals I built. They use a rack and get close > to full pot potation. The pedals are actually a bit more refined now than > when I took the pictures but they may give you some ideas. Someday I will > get around to updating this site. > > http://home.maine.rr.com/spark/ped_main.htm > > Spark

The cam is there for 2 reasons. 1st - space and design considerations. My pedals mount close to the front of my simulated cockpit. Also I felt that it would be a plus if I could mount everything on a single platform. 2nd - (and maybe more important) the cam allows the shock to be adjustable by choosing the pivot point and mounting points of the shock and pedal arm (I had a test cam with lots of holes). These adjustments can result in a huge change in how the shock feels. The initial inspiration for the cam came from F1/CART front shocks. At 1st I tried the shock from a Jetta trunk (which happened to be sitting in my driveway) but this was way too stiff. I went to NAPA and they were kind enough to bring out a box of trunk shocks and I bought the softest one. I really like the hydraulic feel the shock adds (like a brake). Going back to springs just doesn't feel right. Spark "Bruce Millar" <[email hidden]> wrote in message news:[email hidden]...

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> Spark, very nice. I am wondering what the purpose of the cam under > your brake pedal, in front of the shock absorber is? Did you put that > there to change the direction of movement so the shock could be placed > under the platform to save space, or is there another reason? Also, > is the shock an auto part (hood/trunk shock) -- I was under the > impression that those hood shocks were too stiff to be used for this > application, but you are obviously using one. > >

If you using a gameport you can increase the resoloution by using a larger value pot. For example if you use a 100K pot over half its rotation you'd get say 0-50k. Stick a 400K pot in the same arrangement and you get 0-200k. Or use a quarter of the 400K pot's rotation and get 0-100k. The resolution of most pots are fairly good, so as long as the mechanism for rotating the pot is fairly solid, without much play, then the amount of pot rotation isn't that important as long as the resistance range is reasonable. You would probably "feel" more resolution by making sure that the pedals have a reasonably good throw. The biggest limitation is the analogue gamport. It basicly measures the time to charge a capacitor. Put more resistance across, lowering the current, and it takes longer for the capacitor to charge giving a higher count. If you use a small resistance range then you get limited number of counts and poorer resolution. Use to large a pot and it takes too long to perform the measurement (charge the capacitor) giving lags in controller input. Also higher resistance will result in lower current passing through the cables making noise more noticeable (ie the jitters). So in the end, selecting the pot size (resistance range) is a trade off between resolution and controller lag (jitters). There are a few things you can do to reduce the jitters (use the lower resistance end of the pot, short cable runs, good shielding) but there is a limit. If you check the output of most analogue controllers, you'd probably find the resistance peaks at around 50k to 100k. If you can use a digital device, as other have suggested, that may be more what you are looking for. Maybe try one of the gameport to USB converters. There was a good description of the gameport and how digital gamecards tried to overcome some of these limitation at http://www.gplonline.com/tech-talk/hardware-tech.htm but the site appears to be gone. But look at it this way, if you get stable counts of say around 0 to 300 for 3 inches of pedal travel then every 0.01 inch of pedal movement will be detected. :-) HTH Ken Bruce Millar wrote:

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>Suggestions/input/ideas wanted: As a personal project I want to >design a set of pedals that will give a high and fine degree of >control (yeah... buy some high-end pedals -- but I like to build >stuff, ok?). On examination of the pedal internals I have personally >seen (not many) it seems to me that depressing the brake/throttle only >results in the pot turning a small percentage of its potential, a >basic 1:1 movement. I am thinking that a simple gear reduction box >may translate a pedal throw of a few inches into a pot revolution >somewhere between 180 and 270 degrees. I am not an engineer, but it >seems to me that this would result in a finer degree of control, >especially throttle control. In fact, if I recall correctly, wasnt >the old T2 pedal unit based on this design? Do any of the current >mass market and/or high-end pedals use a similar design? Anyway, any >input from this group would be useful. > >