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More DIY/kit potbox musings

995 Views 0 Replies 1 Participant Last post by  EVDL List
G'day All

Having spent the morning considering the mechanics of potbox requirements,
I come up with the following:

3-wire applications:

130 degree rotation throttle-body sensor (3-wire potentiometer) really
requires the body pulley off the vehicles' throttle in order to get that
rotation, the angles that an arm go to become somewhat extreme. It would be
possible to use an intermediate arm to double the arc travel to make it
reasonable, but is more work (cost). A spring on the sensor arm would keep
backlash out of the mechanism. The shaft for the throttle body sensor looks
like it needs to be supported in a bush each side of the sensor.

All up I've ended up with if a 3-wire pot is needed, and DIY is the "way to
go", then it is probably the simplest to modify the throttle body from the
donor vehicle.

Alternatively would be to use a wire-wound potentiometer with a removeable
cover, and "hack" the pot to get a tap-out point after 5k-ohms worth of
travel and set it up as below:

2-wire or hacked wire-wound 3-wire applications:

there are any number of suitable high-quality potentiometers that would
lend themselves to be used in 2-wire applications, they vary from 250 to
300 degrees of rotation (typically around 270 degrees), in 20k, 22k and
25k-ohm values. By using the first 60 degrees or so of arc it is simple to
get the 5k-ohm 2-wire potentiometer (technically a rheostat, with 2 wires)
controllers need. In addition there are 10k, 130-degree throttle body
sensors that could be used with a lever across 65 degrees of arc. Bushes
(plain bearings) are readily available to support the outer end of the pot
shaft, or both ends of a shaft for a throttle body sensor.

So now to the kit parts:

So the theory goes: it would be simple to come up with a kit of three body
plates that have enough holes to be able to be assembled as:
3/8" hole to mount a 'pot' with a 5/16" hole in line with it to take a bush
with a 1/4" hole in it, or
15.1mm throttle-body sensor (middle plate) with 8mm bushes in the front and
rear plates and
enough holes to mount one or more limit switches for zero throttle and/or
full throttle.
In addition a lever arm that is able to be formed up with the 1/4" or 8mm
shaft clamp, long enough to get the cable travel length across many vehicles.
If a throttle body sensor is used, an 8mm shaft with a flat on it would
also be needed, along with two bushes.
To complete the kit, cable sheath clamp, spring/s, 4mm or similar threaded
spacers and a cover plate.

The kit could be assembled left or right hand, with the control lever
between the plates or on the end of the shaft beyond the face plate. Limit
switches where required. Cable sheath attachment and return springs holes
built in. For the little extra cost to get it, done in stainless steel.

All comments welcome


[Technik] James