String Potentiometers?

[Kirk Feldkamp]

Hey guys,

I'm working to put together the data system on my shifter kart, and I was hoping someone has a good lead on string potentiometers for use as a throttle position sensor. I've found a few online... AIM, Racepak, and McMaster sell some, they all appear to be the UniMeasure pots... but they're all about $200-$250. Anyone have a source for a more economical string pot sensor?

-Kirk

[Kirk Feldkamp]

Hey guys,

I'm working to put together the data system on my shifter kart, and I was hoping someone has a good lead on string potentiometers for use as a throttle position sensor. I've found a few online... AIM, Racepak, and McMaster sell some, they all appear to be the UniMeasure pots... but they're all about $200-$250. Anyone have a source for a more economical string pot sensor?

-Kirk

[murpia]

Why use a string pot? They are prone to vibration issues and aren't that precise.

A better and cheaper option is a rotary throttle position sensor off any road car built in the last 20 years.

Regards, Ian

[Kirk Feldkamp]

It's a linear slide carb (before the days where there was a TPS sensor on a motorcycle), and the pedal mounting doesn't lend itself to using a normal rotary pot. I actually have a new AIM rotary throttle pot sitting in a box, but I haven't been able to bring myself to use it yet. The sensor isn't being used as a load input in any way, it's just a DAQ input. In other words, the potential for a small amount of mechanically-induced signal noise isn't that big of a deal. I've seen a few "intermediate" rotary TPS sensor setups that sit in between the pedal and the carb, but haven't found any for sale. I would go down that path myself, but the time and effort to rig up such a setup seems like it could better be spent elsewhere... assuming I can do what I need to do with a string pot.

-Kirk

[Charlie]

Might seem a big wonky but you can always put a lever arm on a rotary pot, and calibrate accordingly, as a cheap solution.

[MalcolmG]

or put a cylinder or throttle bellcrank onto a rotary pot and run a string/cable off that

[Mike Cook]

I agree, and easy way to do this is just put a small lever arm on the rot. pot and have a drop link to your throttle pedal. I see this all the time in military trucks with active suspensions, they use a rotary pot to measure control arm movement.

[Kirk Feldkamp]

Hey guys, thanks for all the comments.

Charlie and Mike: Yeah, I've thought through those options of how to make a 'standard' rotary pot work, but was trying to avoid having to go down those paths.

Malcom: You just described a string pot, hence why I'm trying to find one. I'm just trying to find one that's not stupid expensive. http://fsae.com/groupee_common/emoticons/icon_smile.gif

-Kirk

[MalcolmG]

exactly, go to a junk yard, get a throttle body which still has a TPS on it, remove TPS and throttle bellcrank and attach the two together. Cheap string pot, done.

[Yellow Ranger]

http://www.pegasusautoracing.c...tails.asp?RecID=5121 (http://www.pegasusautoracing.com/productdetails.asp?RecID=5121)

that's a bit cheaper