View Full Version : Throttle quadrant -- creating a proper arc
12-30-2011, 05:10 PM
I'm trying to create a six-lever throttle quadrant, and as my first "build something" project I'm worried that I might have bitten off a bit more than I can chew as there are a few mechanical issues I can't think of a solution for.
I want to create a box that has your basic six levers sticking out, and the levers sweep on a 90-degree angle. Kind of like that Saitek quadrant, if you know what I'm referring to. Anyway -- I purchased six rotary potentiometers, but I immediately have a couple issues:
* If you stack them end-to-end, with the direction of rotation the same as the direction the levers will rotate, they are kind of long: about one inch per potentiometer! That's a fine distance for every two, but I'd like to have the two throttles, two mixtures, etc. closer to each other than that.
* The potentiometers rotate 270 degrees, and I'd only be exposing 90 degrees of rotation. I haven't worked with potentiometers before, so I'm wondering if that leaves enough fidelity in the controls (10-bit ADC if it matters).
For problem 1, I had two ideas. I could stack them so the bottoms actually face the bottom of the box, and this would move the plane of rotation to be parallel to the bottom -- I'd need to create gears to go on the pots and the levers, to transfer the angle of rotation. I suppose I could make a 2:1 gear ratio if I was to do this to solve problem 2 as well, but this is really my first mechanics project and I'm really worried that at that point I'd have bitten off way too much.
Has anyone tried to do anything like this before and, if so, how did you deal with it? The other thought I had was to stagger the potentiometers slightly -- for the two throttles, the left-hand throttle would be further back than the right-hand throttle, and then make two different-sized levers, then repeat that for the mixture and propeller speed. Would this be a workable solution?
Any advice on solving either of these problems would be greatly appreciated. I'd really like to get this done just so I can prove to myself that I'm capable. As far as complexities of building, I have access to a 3D printer and thus have pretty high resolution in terms of measurements I can use.
12-30-2011, 07:15 PM
Consider using slide potentiometers, you would have more options when connecting your throttle/mixture arms.
12-31-2011, 01:39 AM
Firstly, I will tell you upfront that even with a very good idea of what you are doing, it's going to take you months of planning and trial and error to get a working result that looks the part.
Regarding slide potentiometers, I could be wrong, but I have never liked the idea of using them, because I do not feel that they would follow a linear path for a lever that has a curve in the travel. I would prefer to use gears.
Regarding gears, I would use the Knex medium red gears and smaller gray or blue gears. They will work fine. If you have time and money, you could experiment with higher quality plastic or metal gears, but I assure you the KNex will work fine.
Regarding pot shafts, they are very easy to cut to length with a fine toothed hacksaw blade. I place the shaft in a clamp and cut. It's very easy. You do have to make sure you have enough shaft to support the gear.
When using FSUIPC, I think even with minimal exposure to the rotation of the pot, you would still get sufficient resolution, but the more exposure the better. You'll get it with the gears I mentioned. (Smaller gear on pot). Just make sure travel of the thrust lever does not make the pot meet its limits, as that can wear the pot out prematurely.
Regarding the stacking or placement of pots........I would have to take a photo of something to give you an idea.....it's not as hard as it seems, but it does take careful placement. You can basically mount the pot for one thrust lever forward of the thrust lever and mount a pot towards the rear for the other, etc, etc so that they are not in the way as far as spacing is concerned. I'll try to snap a photo or draw something up to give you an idea.
One of the most challenging aspects of doing multi thrust lever quadrants with any potentiometer is learning to calibrate them because not all pots are the same and they usually have dead areas towards the beginning and end that you have to compensate with by making sure those areas are not included in the full idle or max range of your physical levers.
What you're attempting is very difficult, but I encourage you, because the stuff that is out there doesn't cut it and the stuff that does cut it is very pricey.
Lastly, I don't believe a rotary potentiometer is the same a a linear taper 100k pot, which is what you need.
12-31-2011, 09:09 AM
Thanks for the advice ricardo.
I hadn't thought of using KNex gears -- I was thinking that I would have to design my own and print them out. I think I'll avoid cutting the shafts, since they have a really nice nut on them for easy attachment to whatever I'm mounting them on, and instead stagger them so that they'll fit well. I know what you're referring to with the stacking, I think that's the idea I was trying to communicate myself. It does seem a lot simpler for me than trying to place gears and get them to *not wiggle* (which seems the more challenging aspect).
The pots are linear taper, so no worries there. As far as calibrating goes, I figured that I would (if not using gears) use middle section of the rotation and calibrate them in software. Basically read in the results of ADC and send that back to the driver, which then (affine) transforms that into the desired 0-1024 number. That way they don't even need to be facing the same direction when I put them in!
Well, I have a pretty good idea now of what I want to do. Now it's just a matter of going and doing it!
01-01-2012, 02:29 AM
KNex gears is definitely the way to go, they work and are inexpensive on Ebay. Look around and you should be able to get all the gears you need for your unit for $12-18. I'm not sure how the center of a pot would be visually referenced..........the easiest way to calibrate a pot as far as what position it needs to be in is to place your lever in a full forward position, and with your pot in place, turn it in the direction that it would travel if you were moving your lever forward until it stops. Your lever is at it's max detent and so is your pot. What you now have to do is turn the pot opposite as though you were pulling the lever back until you get a reading......because as mentioned, pots usually have a null or dead zone in the start and ends of their range. You don't want those areas to be part of the rotation. Once you have turned the pot and get that reading, that is the start of it's range and at that point, you want to affix your smaller gray gear permanently to it. There are many ways to do this actually, the method I will show you is just one. FSUIPC is a good calibration tool. I'm going to whip up a short video for you so that I can show you exactly what I am talking about. Give me a day or two.
01-03-2012, 06:02 PM
If you have not already seen this...
You might find it gives you a few ideas.
I reciently finished making a six lever quadrant to replace my two Saitek quadrants. I did mine without gears and it works fine. (I would have preferred to use gears if I could have found some at a relistic price.)
The only problem I had was, without gears I hand no friction. Therefore the weight of the lever on the pot would just drag it down. I resolved this by gluing some foam, the stuff you get from the inside of you mother board box, to the inside of the lid and cut some slits for the levers to slide through, perfect. It also gave a nice finish to it.
Also think about adding some switches and LED's while you're at it.
01-24-2012, 04:56 AM
If you have not already seen this...
(I would have preferred to use gears if I could have found some at a relistic price.)
People sell Knex gears on ebay.........type in Knex and find yourself a small lot at a bargain. I'm always looking for a good lot to bid on. Here's an example of a fairly priced lot......
Knex gears work great and you do get some resistance from them being connected to the pot.......and since they are going to be in the "axle", you can also tension against them.
You will need a red gears to attach to your levers and the smaller gray gears to attach to the pots. The dimensions of the metal plates that the pots are attached to is 2 1/4" inch long by 3/4" inch wide. A 1/4" hole is drilled at one side about 1/8" inch from the end/tip. At the other end you should drill two holes to put screws through to attach to the center frame of the quadrant at your discretion.
Here's a couple of photos of the arrangement for a dual lever quadrant........it's just to give the OP and others an idea.
01-24-2012, 07:44 AM
Thanks for the info Ricardo. I'll keep searching but in Australia I don't seem to have too much luck. I'm in the UK at the moment, for a few weeks, I should try to see if I can get something while I'm here. Mind you, if I do find some it would mean that I will have to build another quadrant :-)
06-05-2012, 06:00 PM
Ah the wonderful trials of building your own Throttle Quadrant... Ive enclosed a couple of pictures of the gears I used for mine my friend. I sourced the pots from Maplins in the UK along with the gear sets. After some attempts at fine tuning the pots in FS I have found a happy medium between a full blown off the shelf unit for 3000 euros and my first Saitek quadrant that always gave my sim ghost keypresses. More than happy to help you along the way, there are some really good resources out there with all the correct dimensions for the throttles127956127957
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