tannji Posted August 20, 2003 Share Posted August 20, 2003 This is probably from way out in left center... but has anyone done a mod to the accelerator cable mechanics such that low rpm acceleration is easier to manage? I am thinking about something that would incorporate a cam, so that when you first get on it, it takes more travel to hit say, 2000 rpm, while the rest of the travel is normal, or even shortened. It is not impossible to modulate your foot pressure obviously, but as you add horse the unintentional wheels spins are annoying, and it seems that if this was modified, it could make controlling aggressive acceleration from a full stop a little easier. Has anyone done this, or am I completely ignorant and there is a part for this on the shelf already, or .... "Idiot, it wont work because..." thanks, tannji Quote Link to comment Share on other sites More sharing options...
jmead Posted August 21, 2003 Share Posted August 21, 2003 Sorry that I can't help you with the specifics, but it sounds like a great idea. I've wished for this very thing many a time. It wouldn't be hard to do, but it would be hard to do simply and reliably. I'm interested to see what ideas hybridz comes up with. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted August 21, 2003 Share Posted August 21, 2003 I've seen linkages with a cam type 'wheel'. Don't remember where or when, but have a walk around a JY and look at some different vehicles. When you find one, pull it off and adapt it, or just take your one, cut it and weld it back together with an offset (so that the mount to the TB is no longer in the center). You will have to just tack it in place until you find just the right offset, breaking the welds if it isn't what you want. Tim Quote Link to comment Share on other sites More sharing options...
tannji Posted August 21, 2003 Author Share Posted August 21, 2003 I have some ideas that should work fine... just wondering why I havent seen this discussed or done before... is there a tech or performance reason that would prohibit it? I can even visualize several ways of doing it, one way that would allow "locking" the apparatus in the stock configuration, should that be necessary. building adjustibility for fine-tuning should raise no problems either.... I agree that the feedback here should be interesting.... tannji Quote Link to comment Share on other sites More sharing options...
tannji Posted August 21, 2003 Author Share Posted August 21, 2003 Tim, that is part of the mech I was visualizing... except I would want only the lower RPM's to have the cammed pull. The extended travel of it would probably need to be stock ratio or even slightly higher. I was considering part of it to actually be in the cabin, modifying the stock pedal design. tannji Quote Link to comment Share on other sites More sharing options...
Tim240z Posted August 21, 2003 Share Posted August 21, 2003 Well, that's easy then: Just find spring that is the right tension, and place it between the pedal and the cable (so that it compresses when you push the pedal). That way, with the spring slightly weaker than the spring on the TB side, when you push the pedal, some of the pedal movement will be compressing the spring, some will be pulling the cable. Depending on the length and stregth of the spring, will determine when the spring is totally collapsed and normal (to WOT) pedal travel will occur. Tim Quote Link to comment Share on other sites More sharing options...
tannji Posted August 21, 2003 Author Share Posted August 21, 2003 So, dont remove or modify the cable at all, just add a resisting tension to the pedal?? If that is what you meant, it seems that would make the pedal throw require more effort, which will lessen the finer motor control you have over your foots travel. an instance where that would be a problem is on takeoff, you hit a minor bump or pothole.... turning the normal throttle assisted lurch into a full fledged burnout..... If you meant it as the spring is between the cable and the pedal.... I think you need to explain it a little more to me... thanks, tannji Quote Link to comment Share on other sites More sharing options...
Tim240z Posted August 21, 2003 Share Posted August 21, 2003 I'll try to explain: The cable mount on the inside of the pedal right..hooks in from the front, opposite side of the pedal arm to the firewall. So take off the cable from the pedal, put a spring over the cable, then a washer (cut a slot in it) over the cable so that you could hold the bottom of the spring, and the 'top' of the spring (and washer) would be up against the end of the cable (where the mounting ball is) Now place similar washer on the 'bottom' of the spring, and replace the cable, with the spring on the driver's seat side of the pedal. Now the spring, remember, is weaker than the main spring at the TB. So when pressing on the pedal, both the spring compresses and the cable pulls, but the compression of the spring is 'using up' some of the pedal travel that would usually go directly to the cable. If the length of the spring is correct, then the spring would be fully compressed at 1/2 throttle, at which point it would be a 1:1 ratio again. This is purely theoretical, and will take some experimentation with different springs, but it is acheap enough effort that it may be worth while. Tim Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted August 21, 2003 Share Posted August 21, 2003 I think Mr. Tannji is on the right track. Springs and such would be very difficult to manage and create a predictible and smooth throttle action. I have wanted to do the same thing with my setup, because 4 throttle blades opening at the same time gets real touchy at low RPM. Here is an ideal that is just on paper. The nautilus shaped cam gives you a long lever at initial opening so response can be gentle, and as you rotate the cable off of the cam, the rate gets progressively faster. There might be some car that uses this already? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted August 21, 2003 Share Posted August 21, 2003 Yeah....I've seen those before...just can't remember where Tim Quote Link to comment Share on other sites More sharing options...
tannji Posted August 21, 2003 Author Share Posted August 21, 2003 Greimann has the essence of what I am thinking about.... but I thought about a dual approach, camming the pedal directly with various "pinouts" in the cam, then another adjustment near the carb (or in my case, throttle body). So, I would be able to adjust the curve (in both senses of the word = ) at the pedal, and have a cable tensioner/length adjuster at the TB, also cammed to allow control over the complete "throw" of the pedal, preventing the second portion of the throw from being too sensitive, also preventing the pedal from bottoming out before WOT. Any feedback now that it is a little more detailed? tannji Quote Link to comment Share on other sites More sharing options...
tannji Posted August 21, 2003 Author Share Posted August 21, 2003 Actually, both cams could be at the TB, on the same axis and axle.... this would be simpler, and easier to adjust. Slightly more design work... but hey, getting there is the fun part, right? tannji Quote Link to comment Share on other sites More sharing options...
jmead Posted August 21, 2003 Share Posted August 21, 2003 I see what you guys are saying, and it makes sense. There would be a few flaws: First, it lengthens the overall depression of the pedal. This may be desirable; I guess it depends on what you want. Personally I would prefer a system that only decreases the force necessary, thus allowing more accurate control. And second, it would be difficult to "tune". If you wanted to change any of the characteristics, you would have to design a new "cam". There may be a way around this, but not any simple ones that I can imagine. And thirdly, well, I dunno, I knew there was something else but I lost it. It looks good through. I'd like to see if anyone pulls this off. Pics are necessary, of course. Quote Link to comment Share on other sites More sharing options...
Guest Thurem Posted August 21, 2003 Share Posted August 21, 2003 These systems are more common than you might think. Some cars actually use the system for the opposite effect, to make them seem more punchy. I've seen this (like Greimans drawing) on a big BMW, and some dirtbikes will have a ramped cablepull built into the throttle grip. It would be cool, but stupid expensive, to use an Eddie current dyno and graph the power output at different throttle openings, then design the throtttle mechanism for linear power response. All in all somewhat useless, you know you're just gonna floor it anyways, sideways or not. Also some cars come with fly by wire these days, so you could change throttle response in software (ie in a "chip"). Thure Quote Link to comment Share on other sites More sharing options...
JoeinCA Posted August 21, 2003 Share Posted August 21, 2003 yeah... Get yourself a Radio controlled car servo. ( the nice strong competition servos. Or the big beefy ones that are used on R/C sailboats to turn the main sail). Some of the the radio systems have exponential control on them, i am sure you could design an electrical circuit that would sense the position of the pedal, and make the servo pull the throttle on the carb. or you could use linear actuators, but they are slow, and if you lose power when they are open... you are stuck WOT. with the servo , you can set up a safety spring just like on a cable setup, and it will pull the servo back to normal... hehe, i may have to set up my car to have remote control throttle... just for fun ... could you imagine seeing a guy with a R/C car transmitter at the dragstrip... oh the hilarity... maybe i could use the pedal from my PS2 steering wheel setup... ok.... if you want complete control of all aspects of the throttle... fly by wire is probably the best way to go. I wish i still had my M8 racing transmitter.. i could plug directly into the reciever to control it... too many ideas how to do it... i need to stop and get some paper. thanks for the inspiration, later, Joe Quote Link to comment Share on other sites More sharing options...
tannji Posted August 21, 2003 Author Share Posted August 21, 2003 you guys kinda missed where I stated that each of the cams would be adustable.... multiple pinout points on each cam.... so it isnt necessary to redisign cams, just have multiple connection points on each cam, with a tensioner and cable length aduster to take care of the cable's resulting movement. simple, one size fits all, and much more reliable and probably less expensive than trying to use actuators and variable potentiometers. tannji Quote Link to comment Share on other sites More sharing options...
JoeinCA Posted August 21, 2003 Share Posted August 21, 2003 yeah... that is a good idea.. but i like reinventing the wheel I found the specs of the servos that i have available: INCLUDES: One Standard Heavy Duty Servo w/ Z Connector SPECS: Dimensions: L:1.54" x W:0.79" x H:1.42" Transit Time: .22 seconds/60 degrees Motor: Standard 3 pole Weight: 1.59 oz Torque: 50 oz/in Deadband: 6.0 micro seconds I dont think that it has enough Umph to do throttle work. this one would probably do the trick: INCLUDES: One Microlite servo Servo mounting hardware, One X-shaped servo horn REQUIRES: Nothing SPECS: Dimensions: 1.06" x .49" x 1.284" (27mm x 12mm x 33mm) Weight: .71oz Torque: 43oz of torque @ 4.8v, 54oz of torque @ 6v Speed: 0.23 @ 4.8v, 0.18 @ 6.0v http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCHB6&P=0 now that i know that i dont have a good enough servo, and that it would cost more than just picking up a throttle cable... i dont think that i will do it tomorrow. maybe later. Joe Quote Link to comment Share on other sites More sharing options...
tannji Posted August 21, 2003 Author Share Posted August 21, 2003 If you ever do it using that type of servo.... be sure to let us all know! pretty trick, to be sure. It would make me a little nervous, personally... but I would love to see it done I am going to use servos and retention springs in the hatch and bonnet, as I want to convert to remote entry, and possibly shaved handles and lock cylinders..... not sure about that yet tho... If I do, the license plate will be hinged to cover terminals for a remote charge station for the battery, just in case . Anyone know off the top of their head where to get the kit that allows you to alter the length of a throttle cable, and put a new head on it? I have seen people talk about it, but dont remember the name of it to search for it. The more I think about this, the more I think it could be done easily and cheaply, and finely adustable, to boot. I wonder if Ross wants to add a new item to his inventory??? tannji Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted August 21, 2003 Share Posted August 21, 2003 Tannji, I think you are going to have to build your idea. I just can't picture the double cam and pinout description. As I was thinking about it, you don't actually need a nautilius shaped cam, a circular cam with an offset center pivot would work too. A good throttle cable is made by Lokar, which can be purchased from Jegs: http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4223&prmenbr=361 Electronics are fun to think about, but in practical terms, you just can't throw together something as vital as a throttle linkage with model airplane parts. The safety factor alone is enough to concern me, let alone the technical complications. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 21, 2003 Share Posted August 21, 2003 Check out an Lt-1 throttle body and linkage. It has the cam effect you are talking about. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.