Custom throttle question

[Krusty]

I broke out the Legos (TM) and made an inventory of my meager selection. I've got well over a thousand, but poor variety in that number. I only have 5 cogs, 2 sets of 2 and 1 large (using it as a control handle at the moment). I can only come up with so many combinations to use them with.

So I'm thinking of a 3-axis unit, because my pedals are only using 1 and I can piggy-back them onto that without needing to buy a USB convertor.

So far I've got 1 moving throttle arm and 2 knobs/dials that turn on the front of the unit. That's the optimal design with the parts I have.

What I'd *like* is to have a dual-throttle with side-by-side arms. I'm still mulling over that, but at least I've got my fall back design.

I don't have any pots or wires yet, I've just broken the Legos out of their deep storage and started working on the design.

I'll snap a photo or two tomorrow and show you the "fall back" design. I'd really like to get side-by-side though, for bombers, P-38s, 110s, and even the occasional Mossie ride!

I'm thinking throttle, RPM, Elev trim for the 1 throt/2 knobs setup. I'd like throttle/throttle/RPM for my "ideal" setup.


[Okay, well my "ideal" is the 4-throttle quadrant unit from CH, but I ain't rich. I'll settle]

EDIT: D'OH! FORGOT TO ASK THE QUESTION!!!!

Is there any drawback to mounting the throttle arm or knob directly to the pot? Almost every design I see has at least 1 gear exchange between the control and the pot. Is this just design similarity, or is there a reason? It might be easier for me to glue the throttle arms directly to the pots but I don't know if that'll harm them in the long run.

[Ghosth]

I think krusty the reason for that is that pots are not designed to take the stresses of the actual throttle lever.

If its mounted on a solid pivot point, it can't twist etc and break something in the pot. If you mount it right to the pot, any little knock or twist could conceivably destroy the pot.

If the gears are too big a hassle consider the old tried & true string or direct mechanical connection.

Where an extension of the handle beyond the pivot gives you a lever, tie string to the end of that. make a similar lever on a wheel at the end of the pot, and a spring to hold the tension. Pull throttle lever up pulls the string one way, pulling the pot wheel. Moving the throttle lever the other way pulls it back, or lets the spring pull it back. You get movement, with no side torque or twist on the pot itself.

[Krusty]

Okay, good point. I'll see what I can think up then.

[HomeBoy]

Krusty,
If you have an old inkjet printer (those are notorious for stopping to work in a year or two) , those things are loaded with gears.  That is my primary source for gears.  If you take one apart you'll see what I mean.

[Krusty]

Brilliant idea! Sadly, all the inkjets in the house are 1) functional and 2) the property of my family members.

Anyways here's the pics I promised. It's not refined, as I wanted to get the basic mechanism down first. The hose reels are excellent for using as mounts, as they have a larger area and hold the rod for a longer span, and in a tighter grip. They also add a bit of friction to the mostion, so that the throttle doesn't slip too much. It does slip, though, as it's heavy. I was thinking of putting in rubber stripes on the side of the white cross-bars, to add friction to the throttle motion arm.



And with the arms removed for better visibility:



I'm not totally happy with the way I got the throttle arm attached to the shaft. I might just end up taking that out and super-gluing it directly to the shaft, and avoiding all the unnecessary parts on either side of it.

[llama]

Krusty,

I don't suppose you've seen this:



The full write-up, with lots of photos, is at:
http://www.simpits.org/articles/lego_thr/lego%20quadrant.htm

-Llama

[Krusty]

I have, and it was part of my inspiration to use legos.

Unfortunately, despite being a Lego kid, I didn't ever get many creative kits. I'm stuck with what I've got at the moment.

EDIT: I don't like the idea of a sliding throttle, either. It irks me. I realize a lot of private planes (Cessnas and whatnot) have throttles like this, but I'd rather have a rocker-motion than a pushing-motion.

[Krusty]

Sorry for not getting a picture sooner.



The black arms wobbled by themsleves. So I added small braces across the top of the "hose reel" pieces. This took out most of the wobble. The pots would go on the outside (I would cut the black shafts to fit properly) and the wheel would have one behind the rest.

The wheel has a small gear turning a large wheel. I figured I'd want this for trim or RPM or whatever. More precise. I had to stick a grey arm on the end of the shaft (shown in photo) to see how how much the gear turned the wheel. The hand crank turns just under 2 full revolutions to go about 200 or 220 degrees on the pot shaft. I might leave the grey arm on there, just to add a "stop" and prevent stress on the pot itself.

I like the twin throttle idea. If I want to set up 2 throttles (for twins or 4-engines) I can. If I don't, I can use 1 for RPM. Or, I can just stick a Lego piece across them and lock them together as one. I designed it with that last bit in mind.

[Blagard]

One other point in the favour of gears is that you can use a larger travel on a rotary pot spindle. Nothing to stop you using a linear pot either using simple levers.

Mind you, in my household whatever you build one evening would become a transformer robot or similar by the time you get back from work the next day!

Best use some super glue when you get around to the rudder pedals