Help with the T45 64mm power set-up pls

[solentlife]

I've built the Hobby King T45 64mm EDF .... the $29.99 kit job ... which is the Lanyu model - known to fly well.... Youtube has many on there.

My DF unit is the stock 64mm unit.
Motor is the 2610 5000kv Turnigy EDF motor
ESC is Hobbywing 40A Pentium, needs higher rated ...
Model ready to go without battery 484 grams
With 3S 1800 LiPo AUW 618 grams
3S 1300 LiPo AUW 597 grams
4S 1500 LiPo AUW 630 grams

Factory recc'd is :
2810 4300kv EDF motor
30A ESC
3S 1300 20C Lipo giving AUW of 560grams ..... (I have never seen a model meet factory weight yet ! )

Test figures ............. using Trakker Wattmeter and Digital balance.

3S 1800 25C = 38 amps, 380 watt, 450 to 460 gram thrust ( 0.74 : 1 )
Theoretical run time max of 2,8 minutes at WOT

4S 1500 25C = 52 amps, 680 watt, 500 to 510 gram thrust ( 0.8 : 1 )
Theoretical run time max of 1.7 minutes at WOT

With these packs - she balances near spot on CoG marks. The 12 gram weight difference making only a change that can be accepted as a safe margin.

I'm jusing compact LiPo's now to get max capacity per weight / size but as you can see the run time is too short. Al;so the LiPo's are running at extreme and I expect to puff a few at that rate of demand. Higher C rating increases weight dramatically adding to the problem.
The ESC will need periods of slow running to cool of .... I shall change it for a 50A - max physical size you could squeeze into the special tunnel for it - unit later when I receive my next boxfull of goodies in post.

What to do ? How to cure this without weight addition at rear end to balance out bigger battery ?

Mid battery point back to CoG is 18cms, from CoG to suitable flat area at tail to add weight is 39cms. Any extra weight x at battery means correction of x * 18 / 39. Example increasing LiPo to a 3S 2100 of about 200 grams means an extra weight of about 55gr at front, needing 25gr at tail.
Thrust to weight ratio now being 455 / 684 = 0.67 : 1 on a 3S .... if I can get a light 4S ...

Ideas guys ?

Nigel

[pmullen503]

Doesn't seem to get much more thrust going to 4s. 3s looks like the more efficient choice.

Have you flown this yet? How much actual flying time do you get with 3s 1800? The 1800 pack may be adequate. How sensitive is it to CG? I assume there is no room to move the battery back a bit to accommodate a larger battery. Maybe the larger pack will need less tail weight than you think.

If you haven't flown yet, I'd try it out with the 1800 pack for even a short flight.

[solentlife]

Originally Posted by pmullen503

Doesn't seem to get much more thrust going to 4s. 3s looks like the more efficient choice.

I agree that the weight penalty may be greater than the thrust increase, but the 4S puts it at the 0.8 ~ thrust to weight ratio.

Have you flown this yet? How much actual flying time do you get with 3s 1800? The 1800 pack may be adequate.

I am surprised at the lack of run time considering I'm close to factory except on the higher kv motor, but that's only 4300 up to 5000kv ... Youtube shows it flying on 3S .... I usually fly to 3mins or so - so maybe it will be enough ... but would like a bit more margin and not driving LiPo to near zero !

How sensitive is it to CG?

If like my other T45 ... they are quite tolerant of CoG so the battery range should be possible.

I assume there is no room to move the battery back a bit to accommodate a larger battery. Maybe the larger pack will need less tail weight than you think.

I am looking at 3S 2200 higher C rate along with a heavier ESC. The ESC can be slid back a few cms to help balance out. Then maybe 10gr or so at tail .... but even with the 2200 - I'm still only looking at theoretical 4.3 mins.

If you haven't flown yet, I'd try it out with the 1800 pack for even a short flight.

That's my intention ... see how she is with the 3S 1800 .... if she flies well on 3S ... then I will go for higher capacity packs, I have some from my 450 Heli that I don't use ... but will need to sort balance out.

Cheers
Nigel

[solentlife]

Now fitted the 70A ESC but it's a real tight fit in that tunnel. It also pressed hard on the elevator cable tubes trapping the cables. I had to move it slightly forward so tubes were not pressed so hard.

Balance with a 2100 3S is not too bad .. let's call it SAFE ! She may need a bit more throttle on landing to keep nose up.

Nigel

[solentlife]

Well I bit the bullet and ordered a 4300kv 2810 motor to swap out the 5000kv .... that way I hope to get amps down and extend run-time.

I have 4S 1600 35C compact packs coming as well - so should be well powered.

The ESC will be swapped out as well back to a 50A smaller job easing the pressure on those elevator tubes.

Once she's flown and sorted out to a sweet baby - the wheels and U/C stuff will be removed .... lighten her up by about 50gr, about 30 of which is nose wheel and servo ... and that will help the CoG and power weight ratio.
A small hook under to use my catapult and bingo.

[solentlife]

As a follow on from my previous asking for help in getting the Lanyu T45 sorted for larger LiPo and better run-time ... the possibility of re-locating elevator servo from front compartment to rear ..
The fuselage has a tunnel for ESC above the ducting. The elevator control cables run there also.
I wonder about shortening cables, set the servo in tunnel behind EDF. That transfers 9gr from front to rear, a total iof 18gr change, with a double benefit that the location aft is 2x the distance from CoG ... so effectively 18gr added to tail and 9gr removed from front.
It may be an idea to have elevator servo split to 2 ?
The removal of the servo may allow the Rx to be set where the servo came from, the battery area enlarged .... giving me the increase desired .... a 4S 2100 ....
This comes from noting the SAPAC version has the elevator servo at rear ... and a larger battery area. The models are similar size and both foam ... with 64mm EDF's. But the SAPAC is rec'd for much larger LiPo ..
Nigel

[solentlife]

4 ultra mini 4.3gr servos on order now ..... reckon I could squeeze a couple in at back end.

Will upload photos etc. when i make the modifications ... show result.

Nigel