Some time ago there was some discussion on producing slide throttle
parts or complete units, I don't remember which, maybe both. Is that
going forward?

If not, there is a machine shop owner who is also a member of our EAA
chapter who might be persuaded to make the parts. He has a NC mill and
lathe. Looking at the parts, could they be more economically produced by
a NC punch press? Would punch press made parts be acceptable? I asked
him about transferring the design info to his NC machines. He said he
could use a dfx file. IGES would also be acceptable, but he prefers dfx.
Since Rhino could produce both, it looks like a match to me.

I don't want to step on anybodies toes, and at the same time I don't
want this effort to just languish. I have hopes that the slide throttle
would be more acceptable to builders if they could buy parts, or the
whole assembly. So, I might be willing to up-front the materials cost
and initial production run if it doesn't prove too expensive. Provided
nobody else wants to do it.

Doc Custer
Retired software engineer and sometime Audiologist
Building RV9-A. Fuselage

Feel free Doc. Do us all a favor and put it into production.
Yes our first ones were NC punch press. Front and back plates
were 3/16th 6061T6 about the limits of the punch press.
Very cheap to make. On the order of $15 each.

Here are some pictures.

3/16th thick square flanges could also be punch pressed.

The 3/8th inch thick  Teflon slide needs to be milled, laser cut
or water jet. Whatever works best with Teflon.

The 3/8th thick aluminum spacer between the plates also needs
to be milled or water jet cut. Too thick for the punch.


Paul Lamar ...No rotor no motor.


If made available this would be a big step in helping me and others with
future implementation.  I hate to be so proletariat, but, what kind of end
cost might we be looking at?

Love the idea, I am much more of an "off the shelf" type of guy (ask
Mistral, since we bought their intake).  This would be great for future
endeavors.  FWIW.

All the best,

Chris

Christopher Barber

Cost is a difficult question. My formula is to take the per unit cost
(materials, direct labor, i.e., machine shop cost, etc.) plus
amortization for the set-up plus overhead. Amortization and overhead
are the big questions. Overhead in this case means essentially storage
costs (see below) as it dominates whatever else is included. The
machine shop owner said for onsey-twosye NC doesn't make much sense as
the set-up is labor intensive and you can do as well with a manual
Bridgeport or equivalent. At the level of 10, NC begins to make sense;
at the level of 25 NC is a clear winner. If there is enough demand you
can schedule periodic (6 or 12 month) production runs ala Tracy's
redrives and there is no storage costs because everything is sold in
advance. If you have to make a production run and store the parts for
several years things get more difficult. The bean counters say storing
something for a year costs 25% to 40%. So if you have to make 25 sets
that won't sell out for four years, you have a considerable storage
cost in addition to the other costs. And the producer (me) might be
stuck with a lot of unsold inventory, a considerable risk which I will
have to evaluate at some point. Might be cheaper to not do NC which is
a shame because NC makes consistently good, nearly identical, parts.

So, to help me estimate costs, an expression of interest from the
potential buyers would be helpful. No commitment, just a statement
that if the price were right, I would buy one. Given this data I can
come up with a projected price, which I will share with the group.
This might generate more interest or conversely cause some to say no.
It might take several iterations to arrive at a firm price.

What should be included? I am assuming a slide throttle for a two
rotor 13B or equivalent with the egg shaped holes in the slide. If
memory serves, this would include the two aluminum side pieces, the
Teflon slide, some sort of attachment gadget to control the slide
(help needed here), the spacers, and the four(?) tube-to-sheet metal
turnings. Is this list correct? Anything that I left out or should not
be included, i.e., additions or deletions? The "kit" would also
include drawings, photos and directions. Some fit and finish work may
be needed ala Van's matched hole kits, especially if some of the parts
are made on a punch press. Where the installation is specific for a
given aircraft it will be for an RV 9 including the A version because
that is what is available to me; the RV 6 and 7 have the same firewall
and so the documents could be expected to apply to them also. If
someone wishes to contribute photos and directions for different
aircraft, I would be willing to duplicate the documents and distribute
them with the understanding that I would have complete editorial
freedom. At the present time I doubt that aircraft specifics will be
required, but one never knows what will turn up. I **hate** unpleasant
surprises! As you can see, I am approaching this as a group exercise.

My next step is to try to get a good **estimate** of the per unit and
set-up costs from the machine shop. With that in hand I will look at
the response and come up with a first price iteration.

My goal is not to make a bundle on this; "overhead" does not include
profit or a living for myself. I am retired which means I no longer
have to make a living.

Why would I do this? Like Paul, it is much better than staring at the
TV glop. Or gambling. Or ... well, you get the idea. Having said that
my resources are limited and this effort will have to pay its own way.

My major motivation is based on the conviction that the rotary is the
best engine for aircraft use and the best way to promote the rotary
engine for aircraft use is to make the process of installing the
engine in the aircraft as painless and as free of Fear, Uncertainty
and Doubt (FUD) as possible. The slide throttle effort is one piece of
the larger solution; here is an off-the-shelf solution to the throttle
problem.

Well, this got a lot longer than I intended. AND it is important for
everyone to know where I stand and what you can expect from me.

Doc Custer
Retired software engineer and sometime Audiologist
Building RV9-A. Fuselage



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