HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 24, 2012, 05:44 PM
Registered User
DustBen's Avatar
United States, NE, Kearney
Joined Dec 2011
2,232 Posts
Discussion
Stopping prop for landing in proper position

I have a flying wing that I want to try out but know I have to be able to stop the prop in the horizontal position to protect the prop and shaft.

Using a Dynam 50amp esc/bec with the programming card, which brake setting do I want?
The soft brake, or hard brake?

Am I completely barking up the wrong tree?
DustBen is offline Find More Posts by DustBen
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 24, 2012, 05:59 PM
I used to like trees
rchank's Avatar
United States, WA, Spokane
Joined Jul 2011
288 Posts
Quote:
Originally Posted by DustBen View Post
I have a flying wing that I want to try out but know I have to be able to stop the prop in the horizontal position to protect the prop and shaft.

Using a Dynam 50amp esc/bec with the programming card, which brake setting do I want?
The soft brake, or hard brake?

Am I completely barking up the wrong tree?
I'm not aware of any way to get the prop to stop in the horizontal position. I use prop savers and haven't broken a prop on landing yet.
rchank is offline Find More Posts by rchank
Reply With Quote
Old Jan 24, 2012, 06:09 PM
Registered User
DustBen's Avatar
United States, NE, Kearney
Joined Dec 2011
2,232 Posts
Quote:
Originally Posted by rchank View Post
I'm not aware of any way to get the prop to stop in the horizontal position. I use prop savers and haven't broken a prop on landing yet.
Ok... that's something I didn't even consider but it's obvious.

The setup is about 200-250 watts.
I'll have to see what I can locate online for a propsaver in this power size on a 5mm shaft. I've seen them on smaller designs up to about 7" props.

Any suggestions are welcome!

I have no idea if this will fly, how to launch it... this'll be an interesting day, soon.
DustBen is offline Find More Posts by DustBen
Reply With Quote
Old Jan 24, 2012, 06:11 PM
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
12,372 Posts
You'll want the hardest brake setting for stopping the prop where you want it, but keep in mind that it's still more of an art than a science. Depending on the motor's design, there are usually no more than two or three positions where the prop wil be reasonably horizontal and then several more where you have a higher chance of breaking something.

That said, if the plane has a decent glide ratio you should be able to just give it small taps on the throttle during your final approach to get the prop positioned how you want it. That's where the super-hard brake comes in; it stops it from windmilling and gives you a little edge in precision.

I've got one particular belly-landing plane where this was a big problem. I kept shredding the whole nose apart because 1/8" balsa just ain't as strong as a beefy wood prop or a 4mm steel shaft. Ended up building a whole new fuse before I figured out how to time it, but I can do it pretty consistently now. I've broken two props total in maybe 100 flights. It's a matter of sort of learning how to finesse the power system as much as anything...
C₄H₁₀ is offline Find More Posts by C₄H₁₀
Reply With Quote
Old Jan 24, 2012, 06:32 PM
Registered User
DustBen's Avatar
United States, NE, Kearney
Joined Dec 2011
2,232 Posts
Quote:
Originally Posted by TP16 View Post
You'll want the hardest brake setting for stopping the prop where you want it, but keep in mind that it's still more of an art than a science. Depending on the motor's design, there are usually no more than two or three positions where the prop wil be reasonably horizontal and then several more where you have a higher chance of breaking something.

That said, if the plane has a decent glide ratio you should be able to just give it small taps on the throttle during your final approach to get the prop positioned how you want it. That's where the super-hard brake comes in; it stops it from windmilling and gives you a little edge in precision.

I've got one particular belly-landing plane where this was a big problem. I kept shredding the whole nose apart because 1/8" balsa just ain't as strong as a beefy wood prop or a 4mm steel shaft. Ended up building a whole new fuse before I figured out how to time it, but I can do it pretty consistently now. I've broken two props total in maybe 100 flights. It's a matter of sort of learning how to finesse the power system as much as anything...
I'm sure the wing ought to glide well. I forget the exact details, but I calculated the wing loading after everything was done (with battery) and the wing loading was like 10.89 ounces/sq foot.
I flew a couple of these on fuel 20 years ago and noticed that they would float forever at a fast trot.
I might just end up catching the dang thing.

I just don't know if I can fast trot anymore.

EDIT: I've got almost the same setup of motor, prop, and ESC on another plane. I might as well start trying the hard brake setting there.

What's the soft brake setting for?
DustBen is offline Find More Posts by DustBen
Reply With Quote
Old Jan 24, 2012, 06:53 PM
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
12,372 Posts
Some planes with bigger props can experience a pretty rough jerk when the prop stops suddenly, so the 'soft brake' is most likely aimed toward slowly ramping up the braking effect to avoid causing damage or maybe loosening the prop nut.

I have a couple Castle ESCs that have very customizable brake settings. The most instantaneous settings are downright scary, even on rather small motors. It's no secret that brushless motors are insanely strong when running, but they can just as easily turn that strength around and crank a propeller to a dead stop almost instantly.
C₄H₁₀ is offline Find More Posts by C₄H₁₀
Reply With Quote
Old Jan 24, 2012, 07:10 PM
Registered User
DustBen's Avatar
United States, NE, Kearney
Joined Dec 2011
2,232 Posts
Quote:
Originally Posted by TP16 View Post
Some planes with bigger props can experience a pretty rough jerk when the prop stops suddenly, so the 'soft brake' is most likely aimed toward slowly ramping up the braking effect to avoid causing damage or maybe loosening the prop nut.

I have a couple Castle ESCs that have very customizable brake settings. The most instantaneous settings are downright scary, even on rather small motors. It's no secret that brushless motors are insanely strong when running, but they can just as easily turn that strength around and crank a propeller to a dead stop almost instantly.
Thanks for your input.
So... beware the hard brake settings... be prepared to softly reduce throttle in the bottom range; got it!
It all makes sense and I "know" this...
But knowing something and understanding it as I apply it is different.

Finding a 5mm prop-saver looks like it'll be a matter of hogging out a 4mm... or maybe I'll get a 5mm prop adapter and spend some time in the shop modifying it.
DustBen is offline Find More Posts by DustBen
Reply With Quote
Old Jan 25, 2012, 09:25 PM
Registered User
Hopewell Jct. NY
Joined Jun 2004
78 Posts
Low tech solution

This is horribly old school and low tech, but it works and doesn't add a lot of weight or expense. On a tractor, I stick a piece of very thin music wire vertically behind the motor mount so it is longer than the prop. Angle it slightly and bend the end over, skid-like, so it doesn't dig into the ground. Makes for some odd landings, but the prop doesn't whack anything. For a pusher I have attached a piece of wire to the leading edge and bent it so it goes the entire width of the wing, out past the prop and back to the trailing edge making a monoskid. Some of the places I fly are somewhat undeveloped (translation: rock ledge, hard scrabble and brush), and the wire skid saves lots of wear and tear on the bottom.

Glenn
vicar is offline Find More Posts by vicar
Reply With Quote
Old Jan 26, 2012, 09:52 AM
Registered User
Joined Jun 2004
839 Posts
I've landed wings with up to 7 inch prop without problem for a long time.

Every 3-4 months I might break a prop. Sometimes you see a bit of dirt on the prop where it's hit the ground. If you can land properly I wouldn't bother trying to blip the throttle to make it horizontal.
Dogzilla is offline Find More Posts by Dogzilla
Reply With Quote
Old Jan 26, 2012, 09:54 AM
Registered User
Toysrme's Avatar
Birmingham, Alabama
Joined Jun 2002
2,969 Posts
unless the ESC & motor are equipped with a feedback sensor (optical or hall effect) there is no way to reliably get the prop to stop in any chosen orientation.

ive found it really doesn't matter what you do. if you're going to break it, you're going to break it. when its time is up, it's up. you gotta pay to play. suck it up, get over it.
the only thing you can really do is design for folding props & use less efficient, stronger props (like sport MAS's. which are virtually indestructible, even on the fuel engines & asphalt runways they smack on)

prop savers are fine on small, non performance motors. but they dont handle much power.
Toysrme is offline Find More Posts by Toysrme
Reply With Quote
Old Jan 26, 2012, 10:51 AM
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
12,372 Posts
The problem with using an indestructible prop is that the load has to be transferred and absorbed somewhere else. The next thing in line is the adapter, and then the motor shaft, and then the motor mount and eventually the rest of the plane.

Folding props are an option, but they tend to be more expensive up-front and they're often harder to find. A prop saver on such a powerful plane makes me squirm; 150W is about the most I'd feel comfortable using one with. I've thrown props off them in hard maneuvers even when using enough rubber bands to render the 'saver' ability useless (prop would break on landing before the bands gave).

I'd say that, short of adding landing gear, your only really decent options are to run a folder or just carry a quiver full of spare props Can't hurt to have extras, can it?
C₄H₁₀ is offline Find More Posts by C₄H₁₀
Reply With Quote
Old Jan 27, 2012, 07:45 PM
Registered User
Joined Nov 2011
114 Posts
you want caliper brakes.
RPTheLefty is offline Find More Posts by RPTheLefty
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question How to stop prop in horizontal position ttucker FPV Talk 14 Nov 22, 2011 01:54 AM
Question position off prop DAVE 1985 Electric Plane Talk 5 Oct 04, 2011 03:10 PM
Discussion Proper Prop for Rimfire 0.10 brianengler Power Systems 1 Jul 24, 2011 08:38 PM
Idea Stop prop in same position it was in when ESC was energized mdennis Castle Creations 1 Apr 17, 2006 11:12 AM
Servo position in take off/flight/landing paraplane_flyer Scale Kit/Scratch Built 0 Jan 26, 2004 09:12 PM