Gavin2407

Good day all

Raptor #2 - (3 months old)
Model - TT Raptor Titan 50 SE
Rx - JR RD921
Rx Pack - JR 4.8V 4500Mah extra NiMH 3/4A (Sanyo cells)
Switch - JR “Switch G” heavy duty
Collective - Align DS610
Cyclic - Align DS610
Throttle - Align DS610
Gyro - JR G770T (G770 3D)
Gyro servo - JR 8900G
Engine - TT 53 Redline
Muffler - TT Redline 3D Pipe

Tx - JR DSX9 (9303)

My new Raptor titan 50 se has finally been built, maidened and engine run in but was still having problems with tail kicking and letting go every now and then. First tried various gains, expo and rates with no success. I removed the canopy due to only to notice that the Rx lights would start flashing after about 30 seconds with no stick movements but almost immediately with any stick movements. I noticed that the canopy was rubbing against the lasting gear which could've caused static, which would've caused signal interference. Not sure but that’s the way I thought about it. I have tried my other Raptors 721 Rx in this heli with great success and no more tail issues. I guess I'm at a loss when it comes to the 921 Rx though. If anyone could have advice or suggestions to the following questions, it will be most appreciated.

#1 - Is the battery pack to "small" for this setup?
#2 - What is the internal resistance of these battery packs or how can I test it?
#3 - Can the 921 Rx work without the satellite Rx’s? (Noticed that it will bind but no movements on servos)
#4 - How can I test the Rx to determine if it is the Rx or my setup that’s causing problems? (It came with the Tx which I purchased abroad)
#5 - What do you guy's use to power your systems?
#6 - What is the average current draw of your setups? (I see mine pulls between 2 and 3 amps with quick stick movements and no binding)
#7 - What current does your battery take in after an 8 minute flights of "normal flying" no 3D?

Thanks in advance.
Gavin

BarracudaHockey

My Feedback: (11)

Blinking lights don't indicate interfence, they indicate power loss.

1. If the battery works with one reciever it will work with the other.
3. No, it must have atleast 1 satilite reciever, as does the 7000
4. Swap it with another receiver

Gavin2407

Thanks BH
Regarding the Rx battery pack, I though it should be ok with both Rx's but it seems that with the JR 921 is more susceptible to a "low" voltage power dip than the JR 721 Rx. I don't have another jr 921 rx to test with but Jr 721 seems to be working fine. I still not conviced this Rx battery pack is ok for my setup though, therefore asked also what evryone else is using. I'm thinking of getting the Hobbico 6.6v 2300mah LiFe battery. What's the pro's and con's with these Life packs?
Regards,
Gavin

BarracudaHockey

My Feedback: (11)

I haven't messed with LiFe yet so I'll leave that answer to someone that has.

It's been my experience that most of the JR/Spektrum stuff drops out at the same voltage.

That pack has plenty of capacity but i really recommend 5 cell packs for 2.4 stuff, if there's a problem with a cell you still have plenty of overhead to power the model.

john josey

Sounds to me that your battery pack may be a bit suspect. I`m using a 4 cell 2400 ni-cad in my sceadu and i can have seven flights with the voltage still at 4.7v with a 1amp load.

I did a little test just yesterday, just to see what it would take to get the RX lights to blink indicating a power interuption. The orange lights stayed solid right down past 3v, i gave up at 2.2v as the servos, although they would work kind of normally, but had no holding power.

My set-up is.....
Jr 921 rx
Cyclic 2x jr 8915
Collective jr 8411
Tail rotor jr 8700g
Throttle jr 8231
Jr 490t gyro

Can you pop off all the ball links to every servo and try moving the sticks around again and let us know if the result is the same ?

As BH said a 5 cell pack is a good idea if you have any doubts at all.

Cheers
john

Gavin2407

Thanks guys

Tested system again the weekend with a new 4.8v nimh 4600mah sub C cells Rx pack that I had spare. made no differance with the JR 921 Rx. Tested with links connected and removed, still get between 2 & 3 amp loads on my setup. Voltage drops to about 4.6v with heavy stick movements. Jr 721 Rx had no issues and was able to get in 4 flights yesterday before the battery monitor was indicating in the orange section. After a quick charge, it put 1900ma back into the pack which means I'm averaging 475ma per flight. I think this is heavy if you (John Josey) can get 7 flights from a 2400mah pack, which would mean you average about 250ma per flight. I'm not into the 3D stuff yet and only doing FFF with the odd loop and stall turns. Will get a 6V nicad Rx pack and test again. What should to "average" current draw per flight be?

Regards,
Gavin

BarracudaHockey

My Feedback: (11)

250 to maybe 350mah per flight depending on flying style and servos.

john josey

I have to agree with BH. My turbine powered f-16 only uses around 280 - 300 mah per 8 min and that has eight digital servos in it !

Theres definetly something strange going on with your set-up. Keep us posted and let us know how you get on.

                                                  cheers
                                                          john

john josey

Just a thought.......have you at any time had the cases off any ofthe servos, maybe to change a gear set or something ? if you tighten the four screws on the bottom too much, that can cause the servo to draw a lot more than it should.

BarracudaHockey

My Feedback: (11)

Hangar 9 makes an inline amp meter, I would obtain one and put it between the battery and receiver and move the sticks and see how many amps you're pulling, then between each servo and the reciever. You can use this to verify no binding at the end points and get an overall health of your system. It will cost a lot less than 1 crash

Gavin2407

Thanks guy's

I have a Hangar 9 digital Amp/volt meter that I use during setup of my heli's. I first thought that you have to add up each servo's current draw to get the total current draw but have since been educated by Andy in a previous post for the correct way to do it. Let me try to explain how I go about my setups and please correct me if I'm doing something wrong. This would be for a new setup. #1 - Setup machine mechanically centred, #2 - Install servos, #3 - Setup model on Tx (all travels 100%, no sub trim, trim tabs centred), #4 - Bind system (all servos centred), #5 - Install servo arms and links (ensuring 90deg link setup at centre), #6 - Amend Tx setup (travels, servo direction, expo, pitch and throttle curves linear), #7 - Ensure no binding at max stick throws (digitals will "buzz" if they bind), #8 - Install Amp/Volt meter between each servo and Rx, ensure same current draw with links attached as without links attached (thus confiming no binding is taking place), #9 - Setup pitch travel mechanically to ensure 0deg at centre and equal travel/pitch at top and bottom, #10 - Setup gyro and throttle last (ensureing equal travel, no binding, direction and limits). Ok..... this is in a nut shell what I do but I believe in a proper setup being done, it took me 2 nights to build new Raptor but about 5 nights to do the mechanical/electrical setup. I find that each servo measured on its own, will draw +/- 0.5 Amps with gentle stick movements but can pull +/- 1.1 Amps with quick stick movements. This stays the same with and without the links attached. If I measure directly between Rx and battery to get total current draw it will be +/- 1.5 Amps with gentle stick movements and +/- 2.5 Amps with quick stick movements, max I got was 3.2 Amps. I again test with and without links attached to check my setup. The servos I'm running are brand new and measure about the same as those on my old Raptor which servos are about a year old already.
Only things I can think off that causing my problems is either a faulty Rx or a low voltage drop causing the Rx to "reset' but I've never seen mine go down to below 3V like John's.
Maybe it's time to give everything a good once over and see if I've missed something but it's difficult to understand that I would've made to same "mistakes" on both heli's. Will keep you posted.
Regards,
Gavin

BarracudaHockey

My Feedback: (11)

Sounds very methodical to me.

Many people just slap these things together,

john josey

Again, i have to agree.

After reading your previous posts again. it all seems to be pointing to a 'suspect' 921rx although i`ve never heard of this before.

Gavin2407

Well. I finally recieved new 6V 3300mah Nimh Rx battery pack yesterday. Did a quick cycle and tested on heli with RD921 Rx, banged the sticks around for all they worth and no "brown outs". Minimum voltage dropped to was 5.6v, current draw was also higher at 3.5Amps max. Don't know if I'll trust this Rx in my heli's though, just doesn't make sense to slap a $1000 heli into the ground because of a $150 Rx. Thanks for all the advice guy's.

chadxp1

My Feedback: (2)

You can do a resistance check on the on/off switch. My 2 cents.