View Full Version : Cowl Flap Control (Design) Completed

10-01-2010, 07:28 PM
This is my cowl flap control design.


Would be suitable for Cessna 172, 180, 185 (tunnel mount would be horizontal not vertical in the Skywagon). There is quite a bit of steel but only one axel for all rotation (accept for the pot).

- 4 to 1 (60t x 15t) gear ratio for 1/4 turn to full rotation on the pot.
- Single axle to keep everything solid
- Sprung control arm to simulate gravity in the flaps
- 5 index nodes for the 5 positions of the flaps (Open, 3/4, 1/2, 1/4, Closed)
- Nodes could be mounted to the control plate or to the other side (tunnel). For ease of repair perhaps keep all mounting to one side though.

A similar design could work for the Water Rudder control. If you minus 3 nodes. I'm thinking there is a node for up and down on the water rudders. That could use micro switches to activate the water rudder (AK - the CFC Mk1). A similar action could be used for tail wheel lock. If FSX has such a command?

I know it seems like a lot for cowl flaps. Bush flying has quite a few weather/pressure changes that make them pretty important. FSX's control is incremental so unlike the water rudders it's one click at a time (up or down). The design can be changed of course to suit. In the Cessna 185 all tunnel (floor console) all move on one axle (accept for the rudder trim). I can't do that for a number of reasons. Mostly for ease of building and repair should something need fixing...

The water rudders are next but are as I said about the same as this control. Then the Stabilizer Trim. Which is even easier.. It's the rudder trim I'm still working on.

More drawings with measurements coming shortly. If anyone has a way to improve the design hop on board...


AK Mongo
10-02-2010, 12:33 AM
Just looking at this, and had a thought. I am all about ease of construction, because I do not have tools or even a local cnc to play with. On the plate that the handle detents into, why not put a pin through the handle, that falls into holes in the plate. Then you can skip all of the scalloping, and save time building.

Your design and planning skills amaze me, I just look at things through the lens of "How easily can I build that".

10-02-2010, 03:09 AM
That was a thought I had too. Remember the clip from the Mk2. The one that was used for the magnet. I was thinking I could turn that into a notching device to fit into the notch (node) on the index. Your suggestion sounds pretty good though. I'm all for ease of construction too. The hardest part of the build is the metal bits. They need to be cut and drilled and bent to shape.

Just as an addendum the index isn't to hard to make. I had at one time thought of using steel plate for it and cutting and bending the index. Instead of the notches (holes in the index) I was going to cut and bend the protrusions. Much like the real one. However a Coping Saw (http://lh3.ggpht.com/_Nc05uTeFuS0/SMFRQ94CidI/AAAAAAAAAFA/FMqGrifijAg/Coping+saw.jpg) could easily handle the scalloped edges. Really quite low tech.. They are quite handy for such work and very very inexpensive (12 bucks at your local home depot (http://www.homedepot.ca/webapp/wcs/stores/servlet/CatalogSearchResultView?D=913330&Ntt=913330&catalogId=10051&langId=-15&storeId=10051&Dx=mode+matchallpartial&Ntx=mode+matchall&N=0&Ntk=P_PartNumber)). If you don't already have one. It is the must have tool for all this work. A jig saw will rip the wood but a coping saw has a thin blade and will make a clean cut (less mess and no sanding afterwards).

A few more words on coping saws. Get extra blades. When cutting thin hardboard in this instance I don't for see a problem but the blades because they are thin can brake on occasion. Remember don't force the blade through the wood to hard. Let the teeth do the work. Practice a few times before trying it on your project. Remember also that despite it's size it is very sharp so keep keep fingers a safe distance away at all times. That's pretty easy to do as you are in good control of the blade.

To make the index

- Drill a hole in each of the corner of the notch (diameter of the coping saw blade width) and then start from the edge follow the line and turn at the drilled out hole.. Piece of cake... (well pie in this case hehe). If you want to get super cool about it you can then file the notch to make it square but not important.

- You can do all the drilling first then cut out the notches with the saw.

If it were steel it would be a hole different ball game (hack saw and small hammer). I'm still trying to think of what to use as an anvil. I had an old piece of railroad track back at my home. It was a short piece. Made a great anvil though.

Just thinking a bit. We should maybe have a TOOLS OF THE TRADE forum here at Mycockpit. I know there is the CNC forum and that's cool for there are quite a number of people using it for all forms of panel making... But there is a need for the rest of us that could use a helping hand building stuff.

There are lots of times I want to know how someone did something. Not a tutorial forum directly but a more basic one.

- What paints to use (can be expanded to include formulas for manufactures paint)
- What drill bits to use
- What saws/saw blades to use

I'm not stubborn just trying to help. If the task seems a bit hard. I may have a way to speed that up :)

The index I've drawn can be a full semi circle and need not be open as I have it. When I started I didn't think of depth spacing but later modified it so the gears are beyond the index. I kept it that way though so you could see behind the index.

I will make another one with AK's idea as you will need to change the angle on the handle to accommodate the bolt. I would suggest a round headed bolt so it will work easily with round holes in the index.


AK Mongo
10-02-2010, 02:40 PM
Ahh...I made a classic mistake. I ASSUMEd (I would be happy to share what Grandpa always says about assuming if you need) that you were proposing metal for the indexer. It would indeed be very easy to build in hardboard, plexi, etc. although I wonder about the durability a little.

10-02-2010, 08:35 PM
Ah .. but then you get back into the ease of building again. Hardboard/Masonite is cheap and easy and even though you are you running a metal rod over it that could be mitigated by a little filing of the rod to knock off the sharp edge where the rod contacts the index. Then it's just a question of not spilling a drink down there. I don't know if you can get a metal cutting blade for a coping saw?? perhaps but cutting metal (complex shape) with a hack saw.. perhaps not to bad..

That means a third design option.. Well we are just talking about the index and rod so not bad.

A metal index is stronger then wood would be (not as flexible) so that solves a another possible difficulty. Not to get to over designee about it. Sheet metal is a bit pricey last time I checked at the home depot. Not that I'm trying to build on the cheep but trying cut costs where possible. Could use a lid from a metal can though. Tomato juice can or something? Recycling can be fun. You would have to use a lid removing can opener not the piercing one though.


If being really slick about it. You could open can transfer/drink contents wash out can then cut the bottom off with a hacksaw then measure out and cut index points into the bottom of the can. Drill out mounting holes and paint (you don't want it to look like a can anymore). Then mount..

This is what it would look like with a metal index.. Not necessarily a juice can hehe

More updates to follow.