Mark Steitle and I were kicking around a couple of ideas
on how to cut the cost and weight of the slide throttle.
He had a double incentive as he is building a 3 rotor version.
Mark even considered making the slide out of aluminum honeycomb
for super light weight.

What we came up with is this:
Since solid 3/8 thick Teflon is over $100 dollars.  Much more for the
three rotor. I decided to
do way with the solid Teflon slide and bond two sheets of
0.032" thick Teflon to the front and back covers after the short
tubes are tig welded on. It can be cut with a box cutter or exacto
knife. Or sheared in a sheet metal shear. It can also act as
a gasket saving those parts. It also saves roughly $75 or much
more in the case of a 3 rotor slide throttle.
The slide itself is thinner and made from 1/4 inch thick
6061 T6 bar stock 2.5 inches wide. 10 inches long. That cuts
the cost, weight  and time machining the slide.

This does away with the 3/8 thick steel button spacer as the
the throttle cable can now be directly attached to the aluminum slide.
Another part gone. Also saves about 1.3 inches in overall length.

The main spacer is also thinner at 1/4 inch thick while it has a notch
in one end for the throttle cable. That notch can be used to cut
the spacer by the home builder with an ordinary metal cutting
band saw and filed smooth. A Saws All or saber saw could also be used.
The notch does away with one difficult set up and one hole.
The throttle cable is sealed with red RTV as it passes through
the notch.

For years I agonizes over making the slide out of aluminum.
The big hangup was the edge friction if the slide happened
to cock slightly in the housings. This was solved by
drilling four small holes in the top and bottom edge of the
slide near the ends and putting Teflon buttons in all four holes.
They can be replaced if they wear.

Paul Lamar


Paul, as an alternative to teflon or aluminum for the slide there are many
familys of UHMW (ultra high molecular weight) with differing compositions
and mechanical properties. The one we used in saw mill equipment was light
blue. it had very low thermal expansion, was very hard and would accept
threads. What we used was generally for a wear strip under  heavymovable
sections of equipment where the thompson linear bearings would be hugeand
expensive, People like AIN plastics or Haines in rocky mount NC were the
supplier back in the day.The cost is 20% of teflon which is really a bearing
material. the teflon in tube stock form used as a bushing for sliding motion
ran without lubrication where aluminum bronze would have needed wipers and
lubrication . The UHMW that  usually comes in white, green  and black is
softer doesnt take threads and expands 1/4 in 8' in the sun. The formulas
that come in light blue and light gray  woul work. Use the same stuff for
the side spacers with an aluminum house flashing shim for clearance. This
would eliminate the possibility of problems with differet thermal expansion
of the slide versus the spacer. The distributor can verify which plastics
are impervious to gasoline and motor oil and the best choice for 200 degree
heat soak after engine shut down. these materials are less expensive if rip
sawn to strips from 4X8 sheet stock  but make itclear you dont want a 1/2 X
3 strip sawed from 3" sheet rather than 1/2" sheet so that you have a glossy
rather than sawed finish on the faces.

george grimes

UHMW polyethylene.
According to McMaster Carr tensile strenth is "Poor".
The worst thing about it is max temperature is 180F.
Not a good idea mounted right over the exhaust manifold.

Paul Lamar