harristweed

I am building a 1":1' scale model of a George Buehler schooner. I'm done with the hull and the houses, but before I set the rigging I need to figure out the radio control part. The general scheme I am clear on and have working. Steering is by one small servo and the other sheets are serviced by continuous rotation winches. For servos I got some cheap ones (Exi B1226) that come with the drums. Works fine, except...

The radio I got is a Spektrum Dx5e. The left stick is a throttle, of course, which I don't need. Even modified to be self centering, I can't seem to get the servo adjusted right. If adjust it so that it isn't rotating with the stick centered, then when I turn the radio off it starts spinning like mad. If I adjust it to not spin when the radio's off, the stick has to be nearly at the bottom when it's on. Is there a way to address this? Is there a two stick radio with a non-throttle stick?

Other issue is that all the modified servos will sometimes just chatter away, very slowly spinning in one direction or the other. It seems as though the controls need more dead space in the center. I can't seem to adjust this out of them at the servo side.

If it's not clear, while I know a great deal about sailboats, I know very little about remote control. I have had astonishingly little luck finding expertise at local shops (Portland, OR).

Can anyone help? Thanks in advance.

Joe

*cross posted to scale models*

starinstripes

I use the throttle for the sheeting drum winch with a dx6i. used to do the same thing. I turn off the receiver first and that fixed it.

Don Z.

harristweed

Don Z,
Thanks for the reply. I'll try turning off the rx first. I hadn't been because unplugging the battery was a relative pain in the butt. Maybe I need to see if some kind of switch can be put in there. Using the dx6, do you have any problem with the non self centering throttle? In general I find the sticks on the dx5 to have very little dead zone. Good for a plane I'm sure, but kind of twitchy for a sailboat. Knowing nothing about RC, I had kind of assumed that I'd be able to set up a bunch of winches with controls to make them run one direction or the other. It's been more complicated than that...

mfr02

Turning off the transmitter first convinces your RX that it has lost signal. With older sets, this would just switch off control, but modern "smart" sets will tell the motor to throttle back. The fact that is a sailwinch does not matter to the receiver, so it winds in furiously. The winch you got sounds like what I used to get when I butchered a servo into being a sailwinch. They worked great back then as long as there was a good, solid power supply, otherwise they tended to creep.
I have started using these and similar - https://www.hobbyking.com/hobbyking/..._45g_0_70.html - which are proportional and have a nice shrouded double drum. They come in a few configurations of turn, with a 1" drum, you pick the length of travel you want and get one with that number of turns. In my Victoria (30" long, about 200 sq in of sail) they work very well for cruising. Mechanically they are great. Electrically, if pressed hard in a racing environment and heavy weather and an extra cell in the battery, the electronics become fragile. Probably down to the components needing to be squeezed into a very small space with the gearbox for the position sensor taking so much room.

starinstripes

Joe,
I removed the spring on my throttle as well and it is very precise with no dead spots. As for an on/off switch I used the dubro Kwik switch mount. It is mounted thru a hatch on the deck

harristweed

So what I needed were continuously rotating winches so as to be able to get the booms way out. I did some butchering of the servos, which was actually really simple. The harder part seems to be adjusting the little dial inside to get it where it's perfectly neutral. They seem to creep. I really like the idea of the captive drums. In fact, getting or making drums at all was a challenge. What I've got now are the servos mounted under a sheet of very smooth plastic with the drums on top so flush that the line can't sneak under to get fouled.

I'll use the switch to solve the runaway servo problem. Perhaps the creeping problem is just the price of using modified servos? I'm also trying to figure out a way to make the throttle stick spring centered. Speaking of butchery...

Thanks for all the help, it's great.

harristweed

Thanks everyone for the advice. Once I started turning off the receiver first that problem was solved.

My problem with the throttle stick is that while I made it spring centered by adding two springs inside (Spektrum won't sell me the the parts to do it), it's so incredibly sensitive that even a small bump to the transmitter starts the servo moving. I feel like I need all the sticks to have bigger dead zones in the center.

Mfr2, with the shrouded drum servos you linked to, if they operate by turning one way or the other with the stick, then turn back to a center position when the stick is released, does that mean you have to keep the stick in one position to keep a sheet at a particular angle? And related to that, with the steering servo, how do you keep the tiller adjusted to a particular angle when sailing? Unless you've achieved exactly neutral helm, won't you always be having to keep the stick over?

Thanks again for advice.

Joe

mfr02

The drums, being proportional, reflect the stick position and are best suited to a TX with an unsprung stick, a ratcheted one is best. Saves wear and tear on your left thumb. One of the winches that I managed to fry the electronics on I replaced the minute card with a cheap ESC - this works like you continuous rotation, but rathe better behaved as it has a bigger deadband. Displacement of the stich changes the speed at which the drum rotates. Back when I was butchering servos, I ran across some robotics websites where something similar was done, but they detailed ways of increasing the deadband. I never bothered, as I reckoned that it was beyond my eyesight and fingers abilities.
With any sail powered boat, steering a straight course without correction is unusual. Look back at the history of model yachts - for the past hundred years before radio, there was a stream of ideas for self correcting steering, weighted tillers, Braine gear, Vanes. And these just try to maintain a fixed heading to the wind by reacting to changes and restoring the status quo. They are in a constant state of self re-adjustment. With a radio you use a feedback loop which consists of looking at the boat with the Mk 1 eyeball and employing the standard right hand thumb to apply minor corrections. Unless you are in truly wide open spaces, wind speed and direction will change every few yards anyway.