I'm about 1/4 the way into building a Jerry Bates bearcat, and am starting to scratch my head about how to sequence the gear doors. The bearcat has inner doors that stay down when the gear is down. I plan to use a retract servo for the tailwheel, a mini servo for the doors, and Lado for the mains. (I only ordered the Lados last Halloween, so I can't experiment yet).

From what I understand, with the Jomar sequencer you can't adjust the endpoints, so it would be a ton of work to adjust one servo to operate both doors well. So....

I'm thinking of trying a JR Channel Expander on a 3 position Tx switch.
Position 0: gear down/door down
Position 1: gear up/door down
Position 2: gear up/door up

This should make the setup a bunch easier, you can set the kickpoint of the retract servo/Lado at position 1, and the kickpoint of the door servo at switch position 2. Plus you can set the door servo endpoints to give exactly the throw you need instead of tinkering with two sets of door linkages. Plus you can run a separate battery for the whole retract side. Down side, there is the risk of hitting position 2 too fast on takeoff and crushing a door.

Of course, this is all in theory since I don't have the Lados in hand yet. And I won't order the sequencer until I hear back on why this might not work.

Any thoughts?

Hi,

Have you checked out the microGear sequencer from [link=http://www.oregonscaleaviation.com/]Oregon Scale Aviation[/link]? I'm using it in my TF Giant Corsair
[link=http://www.rcuvideos.com/video/Corsair-Electrics-Test]MicroGear, Thermacowl and Channel 3[/link]

Chris

From what I can remember, a freind quite some time back used micro switches to sequence gear doors and retracts on his giant corsair. My observation was it worked pretty good. I forget exactly how they were connected but a switch sensed full open on the gear doors, that switch then provided signal to the air valve and set a switch for full gear down. Then that switch would keep the gear door servo from actuating until the gear retracted switch was closed and provided signal to the gear doors, which would close after the gear is fully retracted. The idea was to not have the gear door servo or retract servo hot at the same time, only when one of them reached its limit. Your scenario sounds pretty standard.

Clear as mud?
Edwin

Yup,

MicroGear has a gear up switch arrangement that only will allow the doors to close when the gear is fully retracted.
On such an expensive model this device might also be helpful for your retract system. I also am using it.
[link=http://www.tamjets.com/gearfailsafe.php]Gear Failsafe[/link]

Chris

Chris, nice Corsair, it looks like you have the gear dialed in! Thanks for the lead, I hadn't heard about the microgear sequencer before. I know about the Jomar, but it looks like the microgear fixes some of the Jomar shortcomings. In my opinion, you've got to have end point adjustment otherwise you can spend hours trying to tweak the door linkages to work just right.

I think the JR channel expander concept will work, and I like the idea of using a separate battery for the gear, but it feels like I'd be using the wrong tool for the job. I'll probably go with the microgear, since you know how things usually work out when you try experimenting.

If it’s any help the way I have done it on my quarter scale Bates Sea Fury is; -

Like you I have servo operated inner doors I have a micro switch for each door closing as the gear finishes it’s up stroke. I interrupt the neutral wire to each servo and pass it through the micro switch. The gear door servos are then “y’ed� to the retract channel.

The switches must “make� slightly before the end of travel so that the doors have enough time to fully open before the power is switched off.

m

here's a system that works real good for smaller planes 100% mechanical

Hey rack

Welldone mate!!! Very nice approach in mechanical way!!
Can you send some more pics or post a video of how this system works?
Thanks in advance,
J.R.

Rack,

That is a first class set up. I believe I will use this design in my Mosquito. Boy, talk about one picture being worth a thousand words. You have saved me countless hours.

regards

Paul

thats all i have , i borrowed the pics from someone else

I have several models that have similar door sequences and have used a combination of mechanical and electronic solutions. There are several programmable gear door sequencers on the market - Jetronics and Jet Model Products are two I have used succesfully - that allow numerous combinations of inner/outer door sequencing to take place. They use a single channel input (your gear switch) and output two or three channels - one for the retract servo(s) and one or two for the door servos (these are for separate door circuits, i.e. inner/outer - if you are using multiple servos for each door circuit, you can use a Y harness or Matchbox to drive the individual door servos). Obviously you can also use these on air systems by hooking up the appropriate air valve(s) as needed.

Here is the Jetronics info - http://www.dreamworksrc.com/catalog/...2ba045b6263421
JMP info - http://www.jetmodelproducts.com/landing.htm

A good mechanical method if using pnuematic/air driven doors is to use a closed loop air system that keeps the door open whenever the wheels are down. A button air valve that is mounted within the wheel well is used to close the door only when the wheel is completely within the well. No servo or controller required, just mount the button so that is closes only when the wheel is fully within the well. BVM uses this setup for nose gear doors on most of his sport jets, and makes a ready to install button valve and mount assembly - see here: (towards bottom of page) http://www.bvmjets.com/Pages/Catalog/air.htm

FWIW, I am standardizing now on the JMP units and will be selling two NIB Jetronics sequencers here on RCU shortly, if interested.

Have fun -

Barry

In all of the above, I forgot to address your key question -

The Jetronics unit allows endpoint adjustment of the output channels - so that will allow you to tinker with the door servo channel throws and EPA's(s), but not individually if using multiple servos.

I had a similar issue with a tailwheel retract (servo driven, Y'ed with the main gear air valve servo), I solved it by using a Matchbox, which allows individual endpoint and throw adjustment for up to 4 servos per input channel.

Barry