What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RV-3: Electric Flap Actuator

Ironflight

VAF Moderator / Line Boy
Mentor
Although the stock RV-3 design has simple and effective manual flaps, we wanted to do something different with the interior that wouldn?t really leave room for the flap handle. We weren?t exactly pioneering electric flaps on a -3?.that had already been done by a number of people, including Randy Lervold. Randy used a custom version of the ?standard? linear actuator that Van?s sells, but when we tried to go that route, the response we got back from the supplier was ?we won?t supply to aviation projects?. Hmmm?.ok, I guess we?ll just go to the internet and search for ?DC linear Actuators?.

Here we go ? only about 100,000 hits or so. And this model seems to be pretty standard in the 12 volt world with 120 lbs capacity and whatever stroke length you want (as long as it is even inches) . The unit has internal limit switches that turn off the motor at end of travel, which is very convenient. Unfortunately, for our project, we needed a stroke distance in between an even number of inches, so we had to rig an external ?up? stop micro switch ? something pretty standard in many RV?s. The actuator cost about $100 ? a bargain, and quite rugged.

IMG_6159.JPG


One other modification we had to make was how it attached. The ?fixed? end was pretty easy ? I simply built a bracket of sheet steel, bent and drilled to attach to the seat back bulkhead. The moving end, however, really needed to have a Heim bearing, and the stock actuator simply had a hole drilled cross-wise through the shaft. Fortunately, our airpark has another RV builder with a machine shop in his hangar, and rusty was able to turn an adapter that slipped over the shaft and provided a drilled ad tapped hole for the Heim bearing. For the RV-3 installation, the only other thing we needed was a flap actuator torque tube without a handle, and with a little bracket on one side to attach the motor. This was also easy to obtain ? all it took was a phone call to Russ McCutcheon, the man who builds the stock torque tubes for Vans. It was nothing for him to make up a special assembly for us.

IMG_6113.JPG


As with any new component, we?ll have to see how it does in service over the long haul, but I found that it was a compact and inexpensive alternative to the norm, and since we were essentially building from scratch, it was easy to incorporate. It also has the benefit of being about twice as quick as the normal RV actuator, so the flaps are quite snappy!

Paul
 
I used a very similar actuator for a conversion from manual to electric flaps on the Pazmany I once owned. Served the purpose very well. I think you'll be please with your choice.
 
Randy used a custom version of the “standard” linear actuator that Van’s sells, but when we tried to go that route, the response we got back from the supplier was “we won’t supply to aviation projects”. Paul
Paul, Paul, Paul. "Aviation", "airplane", or anything relating to these words are poison when working with parts vendors. I told them I needed a linear actuator for the trunk of my hot rod show car, worked like a charm. I see I even warned those following behind on my web site. Looks like you've adapted anyway though, nice job.

For reference here is the germane section from my "Airframe construction page"...

Electric flaps
Van's only offers the RV-3B with manual flaps activated by a "Johnson bar" located on the left side of the cockpit. This creates a problem if you want to install a throttle quadrant in a traditional location on the left cockpit wall because the flap handle hits the quadrant unless you mount the quadrant so high that it then becomes ergonomically awkward. Shortening the flap handle is not a good idea, builders who have done that report that the air load at 100 mph is considerable. I therefore pursued an electric flap solution so as to eliminate the flap handle. Being familiar with the RV-8 motorized flap mechanism I thought that the motorized "linear actuator" could be mounted just behind the seatback and connected directly to the flap arm. The electric actuator assembly Van's sells is the same for the RV-6/7/8/9, can be purchased for $280, and has been made by two different suppliers over the years.
I cut the flap handle off flush with the crossbar and had a little u-bracket (which can be obtained from Van's if you ask nicely) welded on the left flap arm near the aft end to accept the end of the actuator. As you can see in the pic I used a spare inboard aileron bracket to attach the top of the actuator to the seatback bulkhead. The standard actuator has 5" of travel which is too much for this application so the actuator needs to be modified. In my case I needed 2.6" of travel. Van's current supplier, Usher, was not interested in making a custom version for me however I found Motion Systems quite flexible and their web site allows you to custom configure an actuator for your application. DO NOT MENTION WORD "AIRPLANE" if you speak with them!
With the shorter travel of course the flaps deploy and stow more quickly, in my case it now takes 3 seconds to fully deploy or stow the flaps... nice! In all this conversion has worked out very well. If you're building an RV-3 I recommend you consider this mod. Quite a few builders have asked me what model I ordered, here are the particulars: model 85615 2.60" stroke, 15:1 reduction, 7400 rpm motor, support bushing, cover tube w/seal, rod end TM-4, type C gearbox housing, 1/4" dia 90 std.
 
I know Randy...and actually, I read and headed that quite closely, and asked for an actuator for the seat of my jet boat (I never ACTUALLY had a jet boat, but ahem....). I avoided any mention of airplane....and then put down my email address, the domain of which is "ironflight". The note I got back said they wouldn't sell for aviation uses....so they actually SURMISED that it was for an aviation use! Dang - I was hoping a computer would be reading the note, not a human! ;)

I probably need to get a no-name gmail account....

Paul
 
Why didn't you just get a stock flap motor from Van's and get a flap weldment with a longer arm so the ratio would match properly?
 
Why didn't you just get a stock flap motor from Van's and get a flap weldment with a longer arm so the ratio would match properly?

Stock Flap motor from Van's = $380
12 volt linear actuator with needed spec's = $112 :D

The way we implement the electric flaps in the -3 without impinging on cabin space is to attach the motor directly to the arm for the left flap - there isn't any real way to change the ratio and fit it into the tiny availabel space.
 
I avoided any mention of airplane....and then put down my email address, the domain of which is "ironflight". The note I got back said they wouldn't sell for aviation uses....so they actually SURMISED that it was for an aviation use! Dang - I was hoping a computer would be reading the note, not a human! ;)
I probably need to get a no-name gmail account....

Wow, that's pretty bad when they track down your e-mail domain! For all they know you have an airplane but ALSO have a jet boat you're working on. Sheesh.
 
Didn't realize the brand-V flap motors were that much now.

The stock F1 MK2 flaps are set up this way, and the ratio is adjusted with a longer arm on one side to get the ratio right. So with unequal length arms and an intermediate point on the side with the flap motor, one can get the proper ratio.

I wanted to completely hide the flap motor arm and linear actuator under the floor so I sketched up a mechanism with an intermediate lever (think RV-4 but with the mechanism entirely below the floor). Should be putting it in a week or so...
 
Back
Top