Twin Star II

[Richard Savage]

I have been flying my twinstar on 11.1v lipo's with 7.2v speed 400 motors. The performance is good.
As always, we demand more from our models and I was wondering if a switch to brushless motors would improve the performance even more and less destructive to the motors.
Would I need two becs?
Can I buy a replacement wing to avoid digging out the wing for the rewiring?
What motors would you suggest?

Thanks

[Alistair Taylor]

Richard

In short - yes, brushless motors (of the right size) will improve the performance as they are more efficient than brushed motors - so you could expect longer flights and better performance from the same battery packs.

You will need two speed controllers, unless you buy a bespoke twin-motor setup (e.g. Kontronik Fun, although these are not cheap at £250). see;

http://www.galaxymodels.co.uk/new/results.asp?subt=Drive%20Sets

I bought a Twinstar MKI with a view to equipping it with two of the cheapy bell brushless motors. They cost £15 or so for motor and controller, and if you bolt the motor on the front of the nacelle, there should be room for the ESC where the can motor was, and you can use the original wiring!

see;

http://robotbirds.com/catalog/product_reviews_info.php?products_id=417&reviews_id=57

and for current draw (approx);

http://robotbirds.com/catalog/product_reviews_info.php?products_id=417&reviews_id=21

You will need to route additional 3-core wires to the ESCs via a Y-lead to control the two motors.

Hope this helps

AlistairT

[Richard Savage]

Thanks for the prompt reply.
Are the bell type motors as powerful as a 7.2 speed 400 brushed motor?

[Alistair Taylor]

Sort of.

They both consume the same power from the battery (approx 10-12 amps) but they do different things with it.

The 7.2V speed 400 motor will spin a small (gunther) prop very quickly.

The bell type brushless motors are better at spinning a larger prop more slowly (8x4, 7x4, 7x5).

A small prop spinning very quickly is good for going very fast, but; larger props are generally more efficient than smaller props, and brushless motors are generally more efficient in electrical terms than brushed motors. So, if you don't need to fly very fast, the bell motor is "better" at turning the power from the battery into forward motion.

For the twinstar, which is a relatively slow-flying plane, the bell motors, turning large diameter props (8x4) would (IMHO) be ideal, as per the review on robotbirds.


AlistairT

[Mike Stevens]

Richard
Have a look at RCGroups forum and do a search on Twin Star II - there are masses of threads on that site from our US friends about upgrades. A simple and cheap variation on your theme is to install 480 motors instead of the 400's and IIRR 7x6 props.
Mike

[Richard Savage]

Thanks for the help. As with most things RC there is no definitive answer, but lots of good suggestions. As stated, it all depends on what sort of model I require as to what motor configuration I use.
Plenty to do and experiment with.
Once again, many thanks.

[Peter Simpson]

Hi Richard,

I have recently upgraded my Speed 400 powered models to Brushless. I have tried several different options from Axi 2208/20 and Castle creations 25A to the really cheap options such as Welgard. I will admit that there is a clear winner with regard to cost versus performance.

Motor - Typhoon Micro 6/20
ESC - Tornado 20 Amp brushless
Batt - Tornado Professional LiPo 1000mAh (or above) 11.1v 25C
Prop - 6x4 for comparible performance 7x4 for super power!

The whole setup inc prop adapter costs in the region of £65 and you won't be dissapointed with performance or duration.

All of the above can be purchased from those very helpful people at www.Overlander.co.uk

[Richard Savage]

Since my original post I have fitted a pair of 1050kv motors and individual 30 amp speed controllers. The two motors and two speed controllers cost £35 in total from ebay.
The motors are producing so much power that I have had to build ply boxes within the foam wings to contain them.
I think that I have now reached the maximum performance that the wings can cope with.
Maybe I need to look for a stronger model now!

[Alistair Taylor]

Excellent :)

Which motors did you get and what props were you using?

My twinstar (MK1) is still languishing in a big box, but it's useful to have info like this in advance of actually starting the assembly/installation.


AlistairT

[Richard Savage]

link
It is good that you have not built the wing yet because you can incorporate the extra esc wiring into the panel before joining.

Props 7X4

Good Luck

[Alistair Taylor]

Zoiks!

Two x 400Watt capable motors on a twin speed 400 model!!!!!!!!

Did it go vertical sir?

Did people land their jet turbines so they could watch you fly?

Tried pylon racing with it ;)

I'm using one motor of about this rating in my 45" Tucano - it goes vertical on 10 cells, spinning an 11 x 7 prop, and drawing 35+ amps.

Mind you, I would imagine yours were not pulling 35 amps each on 7 x 4 props...although between them...

AlistairT

[Richard Savage]

Yes, it is a very exciting ride !

Maybe I need to transfer the powertrain to a different plane.

Can you suggest a suitable model?

Thanks

[Alistair Taylor]

You could try to get hold of the Mosquito, or Moskito (German version) wooden kits from Westfield models;

http://www.westfieldmodels.co.uk/

ALternatively there's the Twin Speedy, although this is a bit dear;

http://www.gliders.uk.com/prodinfo.asp?number=AERO1319%2E01

GlidersUK has a stack of other twin-electric models - Tigercat, ME110, Normal Islander....

So many to choose from.

Alternatively make a Spitfire and an Me109 and find a fellow pilot to have dogfights with :)

AlistairT

[Richard Savage]

Thanks for the suggestions.

Looks like I will be spending a few more hours locked away in the shed!

[Alistair Taylor]

you too huh :)

Just finished sorting my shed out. It's now stacked to the gunwhales with boxes of.....useful modelling items....loosely referred to as gubbins..

Now to finish the models that had grown just a bit too big for the kitchen table....

AlistairT

[Colin Naylar]

Just noticed this thread. I have also got a Twinstar still in the box. What I want to know is how you wire up the motors? Is is 2 ESCs - if so, are they on a Y splitter to the Rx or plugged into separate channels and linked on the Tx computer. My first (simple?) solution was to wire the motors in parallel and connect them to a single 30A ESC - any probs with that? This aspect doesn't seem to arise on the forums that I've read - I'd be grateful for any tips

 Thanks

Colin

[David Ashby - Moderator]

Are you using the stock brushed motors Colin?

[Colin Naylar]

Yes, for starters, I thought I'd try the stock motors. I flew my Easystar for a year or so on stock motor before I fitted brushless.  Its just that I already have a 30A brushed ESC so I thought I could make use of it just to get the Twinstar airbourne - Thanks David

[David Ashby - Moderator]

No probs.

Well I flew my Twinstar on stock motors and it performs perfectly well, you just need one ESC for that too.

A standard speed 400 draws about 12-15 amps tops so a 30amp ESC is ok but a bigger one is preferable to give some margin. (I used a 35amp I think)  

I used a 3S Li-Po and everyone said I'd burn out the motors in 5-mins but they were fine with mixed throttle use. Fly her around full chat 100% of the time and yes, you kill the motors pretty soon.  

I wired up the motors as suggested in the instructions and using the little connector widget they include in the kit. Again it all works as it should. 

[Colin Naylar]

Thanks for the swift reply David. That's great news. I did wonder about a 3S Li-Po and had the same reservations but I don't do full chat all the time - far too harrowing for my old head - so I'll at least give the Li-Po a try. Thanks again.

[Frank Skilbeck]

I converted my twin star (mk1) to Lipo, I used a 3s 3300 mah battery and still had to add a bit of lead to the front. The other problem I had was that it kept throwing the original push on props so i had to buy some prop adaptors.

Flys well though now and I've added an undercarriage, tail dragger, take offs are interesting as there is no airflow over the rudder until it's upto speed so directional control isn't very good. But it takes off easy and flys very well.

If I was building one from new I'd fit brushless motors and separate ESC's so I could mix them with the rudder and get some better ground control

I've just pulled my old twin jet out and tried the 3s lipo in that, not flown it yet but the increase in thrust is quite dramatic, so I'll be giving that a go next. 

[Gaz Elliott]

Okay i have got the twin star and been flying it for about a year now on stock, but they have eventually given up. ( Not bad going ) lots of flying and learning has been had. Now I have clicked alot of the links to various sites and motors but due to the age of the theread and the turnover of products most are not available. Any ideas for a moderately priced motor esc prop set up ???

 

I have a 3 cell lipo 3000mah and some 6x 4 props ( props can be used else where.) I am looking for a marginal improvement in flight to 400 I would like more pull/thrust though. I have looked at the codster site but all the numbers don't mmean a great deal ...easily confused and i have in the past bought motors which have been of no use to the particular plane .

 

All help apprieciated

 

Appreciated

 

Gaz

[Marc Humphries]

Hi Gaz,

 

I used two of these from Hobby King in Hong Kong Tower Pro Combo.

 

DO NOT use the supplied prop though, will stress the 25 A ESC too much.

 

I mounted them in a modified standard TS motor mount by placing the plastic firewall behind the screw mounts so the motor is practically hidden (will post a photo).  The ESCs fit into the nacelle - so you can use the existing two wire power feeds.

 

You will need to route the ESC leads in the wings and use a Y lead to connect them to your Rx.  Remember to disable one of the ESC's red power lead - to ensure that only one ESC is providing BEC power.  I also recommend programming each ESC separately before connecting them together and trying out.

 

I use GWS 8 x 4 props with my existing 7 cell 3300 NiMh batteries and also 3s LiPos.

 

Power:

 

On 7 cell NiMh - 230W

On 3S LiPo - 330W

 

Both options transform the standard configuration in terms of power, flyability and duration.

 

Hope this helps - worth the effort to get better performance.

 

Marc

[Marc Humphries]

Here's how I mounted the motor:

Managed to peel away the plastic mounting from the nacelle, and then drilled new mounting holes in the plastic firewall...

 

Trick is then to screw the firewall BEHIND the mounting lugs, not in front.  This means you have to then glue the motor mount and motor into the nacelle.  Make sure the motor is mounted firmly with thread lock on all bolts - as getting at them will require the whole mount to be stripped from the nacelle.

 

I guess you could get longer self tapping screws and drive in from the front.

Edited By Marc Humphries on 26/07/2010 11:45:22

[Stephen Grigg]

I did this conversion on a Twinstar,used the wrong connectors so the motors started indivdually alternately.Changed the connectors to gold ones,never flew it gave it to a club members and it flies superbly