RPM in 2.4G or 35M ...?

[terry westrop]

Hi all, here I am again, with strange issues with R/C & power delivery.

I've been running a set up on 35m all last year; rpm 8600.

Same motor, esc & lipo on 2.4, rpm 7800.

Tried programming esc several times on 2.4, no change. Tried end points after programming, tried travel adjust, consistent 7800

Am I missing something?

TW

[J D 8]

What RC's are you using ?And is it the same size and make of prop?

[kc]

Assuming the rev counter is the same, I can only suggest it's something to do with the throttle trim setting. Of course that's on the tickover end but maybe it affects the amount of throttle movement the ESC 'sees' when you .progrmamme it

[Andy48]

Posted by kc on 21/01/2016 15:34:17:

Assuming the rev counter is the same, I can only suggest it's something to do with the throttle trim setting. Of course that's on the tickover end but maybe it affects the amount of throttle movement the ESC 'sees' when you .progrmamme it

Every tranny manufacturer has different spec for servo centre and servo travel. This will affect the ESC too.Could be something on changing the limits before setting the end points.

Other thought is that the battery is a year older and may be past its sell by date.

[Bob Cotsford]

Terry, probably a silly question but did you reprogram the esc itself, ie switch Tx on, set throttle to high, plug in the battery, wait for beep, move the throttle to low.

I got fooled on my HK DH110 with this one.

Just a thought, on my Taranis I had 'idle trim only' set on my Carbon Cub, somehow this restricted the max throttle value to a point where the esc wouldn't enter program mode to set the limits.  I set 'idle trim only' off and got the full throttle range at which point the esc recognised the full throttle setting.  Does the esc enter program mode with full throttle at switch on?

Edited By Bob Cotsford on 21/01/2016 16:12:59

[MattyB]

Posted by Andy48 on 21/01/2016 16:07:12:

Posted by kc on 21/01/2016 15:34:17:

Assuming the rev counter is the same, I can only suggest it's something to do with the throttle trim setting. Of course that's on the tickover end but maybe it affects the amount of throttle movement the ESC 'sees' when you .progrmamme it

Every tranny manufacturer has different spec for servo centre and servo travel. This will affect the ESC too.Could be something on changing the limits before setting the end points.

Agreed. If the OP tells us what TX he was using on 35MHz and what the new 2.4 set is (make and models) we should be able to work this out fairly easily via the power of t'interweb...

[gangster]

No need to think complex here. Just set up the esc as you already have have calibrating it to 100%. I assume it will read 7800 rpm. Then go into end point for throttle and increase travel a bit percentage until you get 8600 again.

Providing you calibrate to 100% initially you can then certainly reduce your throttle throw % to get less power it's just the same as not moving the stick so far. I don't see why it cannot work the other way a bit. No need to know the facts and figures about both makes of TX centre and throw cos it's adjustable on a 2.4 well most makes

Assuming that either the battery is up to scratch as it was

Just re read your post Terry seems you might have already tried that

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited By gangster on 21/01/2016 16:45:53

[Andy48]

Posted by gangster on 21/01/2016 16:38:21:No need to know the facts and figures about both makes of TX centre and throw cos it's adjustable on a 2.4 well most makes

Not true. Normal travel for a Spekky is just 80% of say a Taranis for example. With extended limits on a Spekky, you can adjust this to 100%, however extended limits on a Taranis goes up to 150%.

[terry westrop]

Thank you all for your comments, (& hi there Bob from classic aero's). Yes, tried the re-programming as per instructions for that esc, twice. Not sure about the 'idle trim only' but esc behaves per instructions, (throttle up).

Yes, I have tried setting esc at 100% then increasing, both EPA & Travel.

tried 2 lipos, both read 98 & 99%, so cannot questions those. However, I have tried both 2.4 & 35m set ups on the same day to confirm rpm variation. Otherwise I too, would have suspected lipo age.

I'll check where the throttle trim is before attempting another re-program, but I general set the idle trim so that 2.4 operates with lipo attached, ie no throttle.

Hi-tec Aurora 9 R/C 2.4G

JR PCM 10 35M (1990 era)

[PatMc]

Terry, it might be best whilst sorting this problem to compare throttle movement of both Rxs away from the model & ESC. I'd connect a battery to each Rx with similar spare servos plugged into the throttle channels in both Rx's & compare the total angular movements.

Having said that, I don't know what type of ESC you're using but I would have expected the calibration procedure to take care of any difference. Most of my ESCs are Hobbywing (or re-badged versions of HW) & calibration has always worked for me when swapping to a different brand of Tx &/or between 37 & 2.4.

[gangster]

Hi Andy. Interesting difference between Spectrum and Taranis. However it is surely only academic. If you set your esc on your Speccy at what it calls the tx calls 100% then you still have at least 20% to play with. Same would go for every other servo by using the old fashioned ways ( arm length hole choice etc. However this does not seem to help Terry.

I am out of ideas for him other than does it matter. Is there still enough in the power budget to achieve whatever he is looking for with a prop change etc. What do the watts look like. No pun intended

[graeme jones]

Terry - just a thought but could either Tx be affecting the tacho? Try both with the Tx at least 50 foot away.

Graeme

[gangster]

Interesting thought Graeme. Looking at this it is beginning to look unlikely to be anything to do with throw or end point. I have never tried more than 100% but from what Terry has told us there is no fooling an esc. It obviously says max is max don't try to get me to give more.

[Andy48]

Posted by gangster on 21/01/2016 17:56:53:

Hi Andy. Interesting difference between Spectrum and Taranis. However it is surely only academic. If you set your esc on your Speccy at what it calls the tx calls 100% then you still have at least 20% to play with. Same would go for every other servo by using the old fashioned ways ( arm length hole choice etc. However this does not seem to help Terry.

I am out of ideas for him other than does it matter. Is there still enough in the power budget to achieve whatever he is looking for with a prop change etc. What do the watts look like. No pun intended

Not really just academic. Once you start having a servo rotation greater than 60 degrees, the linear movement is less proportional to the rotation. Turning some modern servos too far ends up in them doing a complete 360 degree rotation. Also you could come up against stalling the servo as it binds near the end of travel. Futaba has a slightly different centre point to other makes!

However, you are right, it can be corrected at the servo end, and certainly anyone changing receiver make should thoroughly check all control surface movements carefully.

[Andy48]

Posted by gangster on 21/01/2016 18:23:01:

Interesting thought Graeme. Looking at this it is beginning to look unlikely to be anything to do with throw or end point. I have never tried more than 100% but from what Terry has told us there is no fooling an esc. It obviously says max is max don't try to get me to give more.

I have noticed a dead spot on some ESCs at either end of the joystick movement.This is either due to end points not setting correctly or maybe some deliberate part of the design of the ESC to ensure the ESC cannot accidentally start if the joystick is not quite at its minimum. They may have their own built in max and min, regardless of end point setting. 'Tis a complicated thing....

[terry westrop]

Interesting....never thought to put a servo on the Rx throttle output, will do next PatMc, thx.

I've not experienced this before, hence my initial comment; have I missed anything. I'm quite new to 2.4G so need to ask you guys who may be much more familiar.

I'm using cheap 'rebadged' esc as mentioned above, in general.

I guess I'm accustomed to a certain amount of performance & if I see some deficiency I like to find the reason.

Thx all, TW

[Andy48]

Its an interesting problem, and I for one will be interested to see what you find.

[Steve Hargreaves - Moderator]

Have you tried the ESC on a servo tester....that should give you "full travel" so to speak....

The servo is a good idea too...see where full throttle gets you on both modes

[terry westrop]

Servo is all I have at present....but I am seeking tester for future issues, both with esc & servos.

The tacho reading is very stable & consistent, so I would think Tx will not be causing the problem.

It's gotta be esc 'throw' surely. But why...........

[Owdlad]

Hi Terry,

I can advocate the use of a servo output tester as a useful workshop tool for setting up your servos on the bench as they can save plenty of head scratching, further more when in cycle mode [end to end travel slow or fast response time] it càn help identify potential servo faults........so defo worth the outlay of funds.

From memory I'm assuming your old 35mHz is a JR pcm10?

Do you set the Esc with the throttle trim in its forward position or in its central position.

I've discovered on my graupner/JR 35 meg radio this affects the esc end points

If I arm the esc with forward trim I find the throttling response is like a tap from above half throttle, it feels as if the throttle curve I've programmed in is raised on all points

If I arm the esc with the throttle trim in neutral everything is back to normal but when I move the trim to its forward point I also get an increase in power. Using my servo tester to investigate this anomaly I find that with forward trim my travel adjust is raised to 110% so naturally assumed this was affecting my esc.

To alleviate this on all my electric models I disable the trim function

Maybe that modern 2.4 sets are programmed slighty different to the old yet reliable luddite sets

Owdlad

[terry westrop]

Ok; plugged in a servo to throttle to check throw & yes, less throw on the 2.4 set. Not significant I would have thought however, around 5 degrees. Some of this 'missing' throw was gained by adjusting throttle trim, as advised above. For an IC motor 5 degrees would have little impact at top end.

I then tried to 'fool' the esc by reducing the EPA & travel by 10%. Re-programming & then re-adjusting travel back up.

I seem to have improved things by around 400 rpm, but still not the 800 I was looking for.

I'll keep trying, learning this strange thing called EP.....maybe 2.4 also....

[gangster]

This is most tantalising issue. Probably because I am not in a position to get in my shed and experiment. Whichever way we look at it though regardless of whether it's a 35mhz set using PPM or PCM. Or 2.4 which uses PFM the final outcome into the servo or esc is a good old square wave 1 -2 ms. The wider the pulse the further the servo goes and has been thus for nearly half a century. The finest bit of kit to test this is of course a servo and that 5 degrees has to be the difference. I don't suppose there is some odd exponential or curve set on that throttle channel. What happens if the esc is in the elevator channel.

[terry westrop]

Hmm, firstly thank you 'Owdlad', PCM10 it is indeed & still working fine! I have not thought setting throttle trim midway, but that'll be on the menu over the weekend, (on the 2.4). PCM10 needs no fussing around, just fit & run.

Disable throttle trim....?

Servo tester ordered.

No expo, don't use it. The Tx is new & most is still Inhibited, as factory set.

I will try another channel, just for curiosity. Thank you Gangster, you seem to know your PFM from PCM I see.

[PatMc]

Terry, this post in the RCMF forum might be a clue.
Enrico is a clubmate which is why I recalled the problem he'd had. The link mentions that he solved his problem thanks to help from RCG forum so it might be worthwhile doing an advance search there where his username is Enrico!