Twinstar prop size?

[Steve_Wright]

Okay I am a numpty when it comes to electricery so be nice!

I have a twinstar running 460 ballraced motors, 30amp esc & 9.6v flight batteries. Currently have 5.5x4.5 asp electric props and performance is poor. It was much better on the last set of props but after binning them after a heavy landing ages ago I can't remember what they were size wise.

Anyone have suggestions as to what size to try??

[Mike Etheridge 1]

Steve,

Do you mean 'ball-raced' or 'brushed' motors?

Of course the original Twinstar 2 motors are 400 brushed with very tiny props, They are in fact 130 mm DIA =5.11 inches, but I am not sure of the pitch but it looks quite coarse. That said they don't seem much different to the ones you are currently using?

The brush-less version of the Twinstar must have much larger props?

Mike

[Steve_Wright]

They are carbon brushed twin ballraced 7.2v 460 can motors

[Allan Bennett]

I can't find 460 motors on the internet; can you give us a link?

My TwinStar used to use Speed 480 motors with gearboxes, and now I use AXI 2212/12s on direct drive. Either way it uses 10x5 props.  I'm not suggesting that's the right size for your motor, by the way.

Edited By Allan Bennett on 22/04/2013 08:20:06

[Steve_Wright]

sorry 480's not 460's

[pete taylor]

Hi Steve, have you got a Watt meter? If so, how many Watts are the motors drawing? That will give you a good idea of what's going on power-wise

As a rough idea, you need to be getting around 100 Watts/pound for a good spots model. If my memory serves me correctly this will be around 300 W for the twinstar.

That will be getting on for the limit fo your 30 Amp esc but should be ok.

As a metter of interest, have you tried the original white plasic Gunther style props? They might not look amazing but they perform very well...cheap too!

Pete

[Steve_Wright]

sorry no watt meter. Going to get some original props & some 6" props too, have a play later.

[Frank Skilbeck]

The twinstar goes very well with the original motors on a 3s lipo and 5 x 4 props, but not for many flights and one motor burnt out before the other giving a few seconds of interesting flight before I realised what had happened.

[Steve_Wright]

no 6x4 or 6x5 at the LMS

Now have a set of original props to fit, the actual blade it much wider than the asp props I have, pictures later...

[Allan Bennett]

You need a wattmeter ... it will repay its cost by preventing burnt motors and/or ESCs, and will probably enable you to home-in on the correct prop size quicker too

My 480 motors were running at 11.5A each, on seven NiMh cells. So with a wattmeter you could see which prop size gives you somewhere around that number of amps.

My conversion to brushless was prompted by a motor failure on take-off, which resulted in severe veer left into a bush.

[Steve_Wright]

Well did a bodged up test of the stock props v the asp 5.5x4.5. Had one of each type on either side, suspended the plane in the air and ran up the motors, the asp props produce a fair bit more thrust. So off hunting for some 6x5 and 7x5 props......

I take it a watt meter goes between the battery & esc?

[Steve_Wright]

[Allan Bennett]

That's an interesting way of testing But you still need a wattmeter, because the 7x5 may be getting extra power and thrust by overloading the motor.

Yes, a wattmeter goes between battery and ESC. You need to equip it with male and female plugs of the type you've got on your batteries, and then it simply plugs into both the wires between battery and ESC. You could use a regular ammeter instead, if you have one that can handle the amps we're talking about, but it would connect into only one wire, so you would have to make some kind of temporary connection. An alternative is a clamp-on ammeter, which is just clamped around one of the battery wires to get a reading, without disconnecting anything.

[Steve_Wright]

Just done a little playing again. Seems I have a 35amp esc, and with the asp props on both sides on I am still getting the noticable swing to the right, think my right motor is a bit worn out (the twink has been sat in a shed for 2-odd years and it may have got damp)

So first off is get to the LMS and get some new motors to fit & stick with the ASP 5.5x4.5s (for info the white stock props are listed as 5x4.5) May get a watt meter if they are cheap enough, also have got a pair of 7x4" props of ebay to try too.

[Steve_Wright]

twinstar "parked" heavily again. Was running the new motors and the smaller props, did 1 circuit and lost all control/power and bent/burst the nose badly & ripped out the wing mounts. Wasn't a brown out as it didn't go into failsafe (had left aileron on as it crashed not neutral). My own stupid fault, I have had doubts about the ESC after the last 2 flights resulted in a 2 motor issues but it always tested okay on the bench. Since first crash I have replaced the batteries, motors & Rx. Think the twink is glue-able but l am loosing faith in electrickery.

Edited By Steve_Wright on 24/04/2013 18:15:30

[Mike Etheridge 1]

Unlucky Steve,I have had my Twinstar 2 for seven years now and have had trouble with speed controllers and flight batteries only but have had to replace both the original motors when they wore out.

The worse thing that happened with the plane was when I was bench testing it on an outside table. With the throttle set to zero I connected the battery and the motors started immediately at full speed the plane then shifted and one of the props sliced off the nose supports on my new glasses which were laying on the table! The problem proved to be the speed controller and to date I have had to replace two. The most confusing issue I had was the failure of a speed controller and flight battery together. i could launch the plane with maximum throttle and after about 5 yards of flight the motors would just stop.

My plane is OK now and if you persevere with your plane it should function properly. I will let you know the make of my current speed controller which I bought in Avicraft. It has a heat sink which can be located at the front air-intake and it has functioned better than the original Multiplex speed controllers.

Best of Luck'

Mike

[Allan Bennett]

A receiver will only go to fail-safe on loss of signal, not loss of volts; if there's no volts it has no way of sending the controls to the fail-safe positions. So your crash may have been caused by the ESC overheating and taking down the built-in BEC with it -- or the BEC may simply have failed on its own. Have you been able to check if the BEC is still providing power to the receiver?

I've always used Jeti speed controllers in my TwinStar, so can't comment on the Multiplex ones. But 35A should be enough for two 480 motors. Mine was taking 11.5A per motor when it had 480s in it. Without a wattmeter you don't know how many amps your motors are drawing, but I've just seen some internet data which suggests that even a 6x3 may draw 18 amps with it on direct drive -- your 5.5x4.5 props will be similar to the 6x3, maybe even more amps -- so the potential is there for significantly overloading your ESC with two of them.

[Steve_Wright]

The problem first happened when running the Multiplex props, I put it down to battery issue so swapped them out & also fitted the 5.5x4.5 which aren't far off the multiplex prop size
Getting a new ESC tomorrow, hopefully LMS will have a watt meter I can borrow just to check the current draw

Just found this calculator **LINK**

So the JP 480's I have with a 5.5x4.5 asp prop pulls around 15amps ! (multiplex pull 10.5amps) But output is only 100watts each and input 140watts. Can't remember the ESC make I have but it seems the props are running it close to the limit, doesn't account for the early issues though.

[Steve_Wright]

Any suggestions for a 30A plus ESC? All I seem to find on the web are brushless

[Piers Bowlan]

Would these 30A GWS units do? Here. If your 480s are pulling 15A eash you really need a 40A to 50A ESC to be safe and not risk another 'parked' model. Personally I would go brushless and get a couple of cheap BL motors and 25A Turnigy 'Plush' ESCs from HobbyKing (I have had a lot of success with this brand). Your Wattmeter is a wise investment that will save you a lot of money and frustration for years to come.

[Allan Bennett]

If your motors are drawing 15A each I believe their life is going to be reduced. But I agree that you should be aiming for a 40A or bigger ESC to give plenty of headroom. Jeti still do the JES045 45A model, if you can find a supplier.

[Steve_Wright]

Looking at the calculator I have shot myself in the foot going to 9.6v batteries from the 8.4v, the motors draw an extra 2.2amps.

Thing I am going to source a new ESC and stick on the original props SHould only be pulling 11amps with that setup.

This is my only eletric plane thank god, its all too confusing, will stick to my OS 4 strokes I think

[Steve_Wright]

Just checked the specs of the NiMH packs I have too (I do like to do things back to front!) seems the max discharge rate is 30amps. So the asp props are going away & the Multiplex ones are going back on for sure while I investigate brushless/lipo power options

[Piers Bowlan]

I think most people reading this thread would be asking, why are you sticking with a brushed set up, apart from it is what you have. BL motors will be more powerful, much lighter and will not lose power due to the commutator becoming blackened and pitted due to the excessive current (coz they don't have one).

A BL set-up doesn't have to be expensive, This would be my suggestion although there are many suitable cheap bell type motors that would probably also do the job. This is the Turnigy Plush ESC I would use. So two ESCs plus two motors would cost about £29 plus postage. Not too bad?

Alternatively 4-Max in the UK do a suggested set up for the Twinstar.

You have already replaced the brushed motors, receiver and about to buy another ESC, Save yourself some money and go brush less is my 2p worth.

Edited By Piers Bowlan on 25/04/2013 11:04:34

Edited By Piers Bowlan on 25/04/2013 11:11:38

[Steve_Wright]

I really don't want to spend more on this twink (a bit late now LOL), a new 35amp esc is about £10 at the LMS once this one is reliable it is being used for basic training for my son (it is a bit battered now anyway, won't mind it getting bashed up some more) When he has it I will be getting myself a new twink which will be brushless.