Advice please

[Edward Ward]

HI

Being new to the sport, I thought I would try my hand at electric flight. To this end I bought a Twinstar 2 RR.    The site where my club flies is always quite windy,and the standard twinstar struggled in these windy conditions. So with a budget in mind I have installed 2 standard brushed Graupner speed 480 motors with 2 APC 6 X 4 props.   

I also plan to perhaps use a 2s 4200 lipo ( reduced weight ), and I plan to insert cellshield unit with a temperature control probe to protect the Lipo and give throttle shutdown at a cell value of 3v, 6v in total.

Please give me advise on the above setup, and how would the existing speed controller handle the new motor amp pull.

Please help

Ted

[Tim Mackey]

Firstly, if your site is windy, then reducing the weight will possibly make things worse - heavier models will penetrate and generally handle the wind better. There is little real difference between the 480 and 400 speed motors - especiallly if only running on 8 cells ( 9.6V ) 2s Lipo will be only 8.4V.... so even worse.

Pity you did not spend a tad extra and go brushless - very cheap deals available these days and far more efficient.

The cell shield thing ( never heard of it ) should operate on cell voltage detection NOT temperature - as the battery may well never get past barely warm....yet the cell voltage could drop too low.

In flight ( under load ) 3V is too high for LV cutoff - 2.85 to 2.75 is more realistic.

I cant say about your ESC 'cause you dont stae it s spec, or indeed the actual current draw it will be required to handle.

Personally I never liked the easystar - friend bought one without my knowledge, and it only ever came to reallife when I stuck 3s Lipo in it - brushed 480s will take 3s, but prop down slightly. 

[David Ashby - Moderator]

Hi Edward, like Tim I've never heard of the cell shield.

I used to run my Twinstar 2 on a 3S LI-Po and throttled with care so your 2S will be fine. It;ll stay up all day on a pack as large as that - probably 30 minutes with careful throttle management so fly for 20 mins and you'll be fine. The motors will draw about 12-15 amps at full chat so budget for a brushed ESC of at least 35-40 amps. A Li-Po compatible ESC may be programmable and allow for cut-off to be adjusted but as I say you could just fly well within the battery capacity for say 20 mins and then land.

[Andy Harris]

My Twinstar doesn't like the wind. (its not the '2' version).  On a calm day its very docile and tracks well, very floaty in the landings.

Timbo is right.

[birdy]

This is the CellShield.

You can get very cheap B/L motors and controllers here as well as cheap lipos & ESCs.

[Edward Ward]

Hi

Thanks for the help and advise left todate,my thanks also go to birdy for the couple of links left  1 the link explaining the CellShield (saves me the job) and the other to the site that seems to have some very competitively priced gear.

I was hoping to get away with utilising my existing 32 amp Brushed ESC with the added battery protection of the CellShield. But it looks as though I may have to upgrade to a 40 amp one, as I guess the two 480s will pull in excess of 32 amps.

Would it be best powered by 2s or 3s throttled back during flight.

Ted 

[Mike Stevens]

I fly mine on stock motors but an 8 cell Nimh some maybe the ballast helps. It can be a bit balloony in the wind but equally and can be floated around with motors off. In warm weather I get about 15/16 mins on a charge and have sloped it on Exmoor. The only problem with a serious upgrade and speed is that the wings begin to flex quite a lot under G - great trainer and general fun aircraft though.

Mike

[Tim Mackey]

I reckon you would be OK with the 32A ESC if you try a 2s lipo - current draw unloads a fair bit in the air.

Several ESCs these days have a cellshield circuit built in. 

[Edward Ward]

Hi

The as bought setup with stock 400 motors was powered by a Tornado 7cell 3700 Nimh, this battery weighed very nearly  1 lb (450 gramme).

On hand launch and heading into a 10 mph breeze at full throttle it made no headway at all, it just hung there like a kite, untill it slipped into a wing tip stall and crunch. Surprisingly not a lot of damage, this Elapor foam is realy tough. Basically the same thing happened on the next flight, .It was then I decided to upgrade moters props and lipo to reduce weight and hopefully increase power.

Please leave me your thoughts on this?.

[Phil Claridge]

hi there you can use two cheapie bell outrunners with 20 amp esc  they sell now for 10 to 20 pounds each for motor plus esc they fit on to the multiplex mounts easily i ran mine using a 3s 2200 lipo and got good performance with 6by 4 props. ps liked it so much ive worn out 3 sets of motors so far

[Edward Ward]

Hi Phil

New to the Electric scene, is there any chance you could inform me of the code name of the outrunner you used and the wibsite you acquired them from.

How would you plumb them in, ie. would the ESCs be fixed directly onto the motors in the wing pods and would you somehow utilise the existing BEC or whatever, a rough wiring diagram would be helpful.

I realise now that I possibly should have gone the brushless rout, rather than brushed 480s

Ted  

[Adrian]

See http://www.4-max.co.uk/customermodels09.htm

George the proprietor has a Twinstar himself and I have often seen him fly it at our club.

[Phil Claridge]

hi edward follow adrians link that shows you how to do it better than i could. the esc,s go right behind the motors in the pods ihold them in with short bits of tea stirring sticks pressed gently in to the foam.

the motors i used came from planenutz idont know what make or model they were just cheapo 400 can replacements regards phil