The CH products throttle quadrant is a great input device. One of the best features is the swappable lever tops which let you configure as a quad, twin piston, and anywhere in between. Unfortunately, there is no good way to configure for a twin jet; the black lever tops are too thin. What you need is a lever top which spans two levers, so that you get a nice handful when you move both throttles together. Time for a mod. Below are two versions I tried.
Version 1: Sculpey tops
Sculpey tops in action (click for more sizes)
This is the easy form of the mod. It is made of Sculpey, a polymer clay which is non-toxic and can be shaped like plasticine when raw. When baked in a normal oven, becomes hard like porcelain. The finished product is not too brittle, can be carved/sanded as well as painted, and it shrinks only a little while baked. It’s a popular material among scale model builders for forming custom parts.
First, create a cylinder of Sculpey the diameter and twice the length of the desired tops. Cut the cylinder in half shape the ends to be completely flat. Now gently press each cylinder into the throttle levers. This creates the sockets which attach the top to the levers. Bake the Sculpey according to the instructions. Due to the slight shrinking of the Sculpey during baking, the fit on the levers should be quite snug. You can use a file or hobby knife to trim the sockets if the fit is too tight. Once you have completed these adjustments, you can paint or otherwise cover the tops (I used black electrical tape).
Completed Sculpey tops
The result is a little crude, but durable and works quite well. Like the CH products tops, you can easily swap them out as needed.
Version 2: PVC tops with TO/GA or A/T disengage button
PVC tops in action (click for more sizes)
This next version gives a much better, more professional effect, and optionally you can add a thumb operated button for auto-throttle disengage or TO/GA. The effect is a little like the DC-8 throttle levers:
Real DC-8 throttle tops
The basic materials here are PVC pipe and Meccano beams (in the USA they are called Erector, which is just a terrible, terrible name for a toy). PVC pipe is soft enough to be cut using woodworking tools, it can be sanded, can be glued with regular hot glue, and painted using regular spray paint. Meccano is pre-drilled and bendable, which allows you to bolt it into place, and is affordable. Meccano has changed since the 80s when I last played with it – these day the metal is thinner (which is good, as it makes it easier to bend), but also more brittle, which means when you bend it, it can fail and break (this happened to me twice in this project).
Bend them too aggressively, and they fail
The biggest improvement is in the nuts they provide – in the old days they were simple machine screws with hex nuts, but now they give you nyloc nuts, which resist loosening from vibration etc.
I knew this was going to be a mechanically complex mod, so first thing is to do some sketching of how it should all fit together. Sketching is a good way of thrashing out ideas, no matter how nutty, before you commit to buying materials. Here is a page showing a near-final design:
Preliminary sketches (Click for more sizes)
Finally, I settled on the basic design. Each top would consist of a straight PVC pipe joint, bolted to a 9-hole Meccano beam bent into a 90 degree U shape. The ends would be PVC pipe caps. One of the tops would have a push button for the TO/GA function. The final sketch is below. In the end, the final product differed only in the lack of glue between the Meccano bracket and the PVC joint (the bolt was enough), and the lack of cable ties holding the cable to the bracket.
The near final design
Here are some plans if you want to try this mod yourself:
Full plan of a top (click for more sizes)
Building the lever tops
Begin by making the brackets. Start with a nine-hole Meccano beam. Measure the dimensions as indicated in the plan (43mm – 32mm – 43mm), and carefully bend it into a 90 degree U-shape (I used my vise as a makeshift bending break). Bend gently, or the metal may fail. When you are done, check for cracks at the bends – if they have appeared, the part is on the verge of failing, so you should discard it and bend another.
Making the brackets
The next step is to cut the PVC parts to size. Using a tenon saw and a mitre box gives a good result – remember to sand the ends to even them out (sand them by laying the sandpaper flat on your workbench, then swirl the part on the paper). When cutting the junction, note that there is an thicker ring in inside center of the joint. You want to preserve this in the center of the piece, so make two cuts, one on either side.
Cut PVC with woodworking tools (watch out not to breathe in PVC dust)
At this point, you can drill a hole for the bolt that will hold the bracket to the joint (at the very center of the junction – it should go through the thicker inner ring). Bolt the bracket. You can now test fit this part to the throttle – the lever tops should rest on the PVC joint, and the bracket should fit snugly on the outside of each lever.
Now to cut the caps. You will notice that you need to cut a notch to allow them to slot into the junction due to the space taken up by the bracket. Measure and mark the area to cut (see the plan above, it is 15mm x 14mm). This cut can be done with a coping saw, but really it is easiest using a Dremel or similar rotary tool. The trick here is to ‘nibble’ away the plastic rather than trying one large cut (the friction of the spinning bit will cause the PVC to melt, so adjust your speed and stop as necessary). I cut a number of lines straight into the cap, and then ‘ate’ sideways to detach them from the cap:
To prevent PVC from melting while cutting, "nibble" away the unwanted material
Once the cuts are done and neat, you will have the three parts you will need for a top. The caps should fit very snugly into the joint (you won’t even need to glue the caps in).
The parts for one lever top
Fit the parts together and do a test fitting. Ensure that cracks have not appeared at the bend of the brackets.
test fitting the lever top
Check also that the caps fit deep enough into the joint that the two lever tops will not collide as you move them independently. Do this by placing both tops side by side.
Testing the width of the tops to ensure they do not collide
Also think about how you will drive the bolts thought the brackets and levers to attach the tops. Notice in the photos above that there are three holes available on the sides of the brackets. I drilled through the top and bottom holes on each lever so that a bolt can go straight through both levers and the top bracket holes, and the same on the bottom bracket holes (more on this below).
Adding a thumb button
At this point you have the option of adding a thumb operated button. Airliners typically have a TO/GA or autothrottle disarm button on the stick tops, so it’s a nice addition. To do this, you will be working on one of the endcaps (choose the cap based on where the thumb you want to operate the button with rests).
The button you should use is a SPST button (single pole/single throw). You can find suitable buttons at Jameco or Fry’s. These are buttons that close the circuit when pressed, and open the circuit while released. There are many choices of button – your primary concern in choosing is the dimensions. The diameter should be small enough to fit in the endcap, and the length short enough to fit inside the entire top. The button I used is the Valuepro R13-511A-05-BR.
Once you have your button, drill in the face of the endcap to screw the button in, and also make the notch you cut in the cap to accommodate the bracket a little deeper (the button cable will exit the lever top through this space – 1mm or 2mm should be enough). Solder a cable to the button, test the connections, and reassemble your lever top.
Tops reassembled with button installed (click for more sizes)
The challenge now is how to have your new button talk to Flight Sim. I decided to make use of one the throttle quadrant’s six switches (they are actually 12 switches – one for up, and one for down on each of the six grey switches). The idea is to attach the new button to one of these existing switches so that pressing it will be the same as pressing the original switch. However, we want to be able to easily remove these lever tops, so the whole thing has to be detachable.
To solve this problem, I used a simple power plug and socket (like those used to give power from a wall power supply into a small appliance) – these are also found at Jameco or Fry’s, and have two connections (which is what you need for a switch). The male will be soldered to the cable connected to your new button, and the female will be connected to the appropriate switch inside the throttle quadrant. I used this male and female.
When you open the quadrant, you will see the pc board with the six switches attached. Above each switch you will see two soldered connections – use a multimeter to verify that these two close when you press the switch, and open when you let go. I used the top connection on the very left, which translated to pressing the left switch upwards.
Soldering the new connection to a switch
Now drill a hole for the female connector at the front of the quadrant, and solder a cable between the two. You will notice that the quadrant case now refuses to close – there is a vertical wall inside the top of the case which presses down on the switches, and your new connection is bumping against it. Use your Dremel to grind away about 7mm depth (0.3″) in the wall in line with the left most hole in the case.
Making space for the new connection
With the case closed and the lever with the top held in place, measure out the length of cable you need – pull the levers all the way to the back to get the right length. Add 2.5cm (1″) extra cable, and solder on the male plug to the cable. Now you can plug your button to the throttle’s switch.
Testing the plug (click for more sizes)
To test your connection, plug the quadrant into your PC, bring up the windows game controllers dialog from the control panel, select the quadrant, and hit Properties. You should see all buttons off, and when you press your new button, button 1 will light up in the window
Testing the new button
If the button 1 light is always on, then your button is shorted – check all your connections to ensure they are not touching.
Painting and attaching the tops to the levers
Painting PVC is quite simple – use normal spray paint, and apply it in a few thin coats, allowing each coat to dry before you apply the next (applying too much paint at a time will lead to the tops being sticky to the touch). Be sure to mask out the button and cables before you spray, as the paint may clog the button’s mechanism.
Masked, and ready to spray
Once the parts are nicely dry, you can get ready to attach them for the first time. Place one of the tops on the lever, and with a 5/32″ drill bit, drill through the top and bottom holes (do this for both levers). Now repeat the process for the other stick top.
Drilling the levers
Now you can attach the top using a 1.5″ long #6 machine bolt with a corresponding butterfly nut. You will need two (one for top hole, one for bottom) per lever top. Notice that the butterfly nuts and button plug make it easy to remove the tops if we decide to go to a four engine configuration.
Here is the finished product. If you fly three-hole machines (like Thomas’ Ruth freeware 727), you can always build another lever top.
The finished tops (click for more sizes)
If you already own all the required tools, the total cost for this mod should be around $15, plus the cost of the Meccano beams (I got a middle sized set for $25, that has left me with lots of nice parts for future projects).
Read Full Post »