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View Full Version : Question Thunderbird 18, 3s LiPo and Castle Link


FlyWheel
07-30-2011, 06:49 PM
:oops: Probably a silly question but here goes...

I'm programming my TB-18 ESC and want to change the cutoff voltage (I feel 3 volt's/cell is cutting it a bit too close). So I want to set the cutoff for the total voltage of all the cells right? IOW, if I want the cut-off to be at 3.2V/cell I would program the ESC (in "custom") for 9.6 volts, right?

Also, what is the difference between "soft brake" and "hard brake"?

rcers
07-30-2011, 07:26 PM
:oops: Probably a silly question but here goes...

I'm programming my TB-18 ESC and want to change the cutoff voltage (I feel 3 volt's/cell is cutting it a bit too close). So I want to set the cutoff for the total voltage of all the cells right? IOW, if I want the cut-off to be at 3.2V/cell I would program the ESC (in "custom") for 9.6 volts, right?

Also, what is the difference between "soft brake" and "hard brake"?

Yes you would select custom and then 9.6v. I might add unless they are high "C" packs that is pretty high. I don't use 3.2v/cell unless I am using 30C or greater packs.

Other lower C packs voltage drop is much less severe. With the High C packs when they are done you sometimes can't even get a 15 second motor run. This is actually why I never fly to LVC anyway.

Hard brake applies strong power to stop the prop quickly. Use soft brake.

JetPlaneFlyer
07-30-2011, 08:14 PM
Why would you use any brake? The only reason I know of to use brake is for folding props.. I always disable the brake on by models with non-folding props so the prop freewheels.

Is there something I'm unaware of?

Steve

rcers
07-30-2011, 08:27 PM
Why would you use any brake? The only reason I know of to use brake is for folding props.. I always disable the brake on by models with non-folding props so the prop freewheels.

Is there something I'm unaware of?

Steve

Steve folders is the only reason I use a brake. And soft brake usually gets it there so not even sure why you need more brake power except for large propellers.

FlyWheel
07-31-2011, 06:11 AM
Thanks guys. I was just using 3.2V as an example. And I do have a folder on my Skimmer. Also it's nice to know for future reference. :D

Oh, and Steve, is there a reason one would want the prop to freewheel on a non folding prop? I thought that added drag?

JetPlaneFlyer
07-31-2011, 08:11 AM
Oh, and Steve, is there a reason one would want the prop to freewheel on a non folding prop? I thought that added drag?

If a fixed prop or a freewheller adds more drag is the sunject of some debate. In the world of rubber power models a freewheeling clutch mechanism is built in in order to allow the prop to freewheel, so, the theory goes, to reduce prop drag.

I've seen a wind tunnel test tha suggested both approaches might be right, depending on prop pitch. Fine and medium pitched props (IIRC less than about a p/d ratio of around 0.7) gave less drag when fixed, course pitch props gave less drag when freewheeling.... Of course folding props give less drag than any either.

But to answer your question.....On my models I usually want drag when I close the throttle to give an airbrake effect to make landing easier. Anso it gives quicker pick up becaue the prop usually doesnt stop spinning.

Steve

Larry3215
07-31-2011, 08:24 AM
Some of the guys flying larger pattern models with big props will use soft brake at a low setting for extra aerobraking - particularly on the downlines.

The idea is to slow the prop down but not stop it. The theory being that that will create maximum drag.

I played with that some a couple of years ago and it did seem to work fairly well. That was with props in the 22x12 range.

Larry3215
07-31-2011, 08:29 AM
By the way - I do NOT recommend using Castle break set to HARD stop.

Its an absolute instant stop and can do severe damage to the motor, mount or model.

It can unscrew prop nuts, break shafts and rip motors from firewalls.

I ONLY use the soft break and start out at the lowest setting and increase breaking strength in small steps until you get it to where you want it.

FlyWheel
07-31-2011, 04:41 PM
The Thunderbird only has two brake settings: Soft and hard, no "steps". As for the planes that hcurrently use it I have a 'lectric sailplane with a 10x7 folder, AXi 2212/34 + 3s Lipo; and a sloflyer with same setup except a rigid prop. I don't really care about the slow flyer, but obviously I want the folder on the E-glider to stop, otherwise why have a folder?

rcers
07-31-2011, 04:58 PM
Use soft you will be fine stopping a 10" prop.

Larry3215
07-31-2011, 05:22 PM
I shouldn't answer posts when I haven't slept enough - didn't notice it was a Thunderbird. Ive never tried the break on the TBirds, but I agree with rcers, start soft :)