250 expo for 300cfx

wtowns

New Member
Hi! Folks!
Can anyone tell me if it is ok to use expo on the 300cfx. I find it a bit touchy and the radio set up in the manual doesn't show any expo. Or will using expo cause problems with the ar7200bx. I know it says not to use sub trim when setting up but not sure about expo in the transmitter. comments from someone who has done it and how much they used would be appreciated.
cheers
Warren
 

Heliman450

Well-Known Member
Hi Warren, the Forum's a great place to come for help and advice or just to look in on what's being said about problems that others are dealing with.

When I found out how things work, I started by asking "what do I want the heli to do?". If you want wild 3D then you're probably well in advance of needing help with the basics like settings for pitch curves etc. If you want a much more controllable heli as a beginner, look to calm everything down until you're sure of your skill/knowledge level. If you've got a simulator then experiment with different settings until you begin to "feel" or anticipate what the heli is doing and how it's reacting to the weather changes etc. that you can programme in. It will never be exactly like the real model unless you can go through all the advanced settings and tweak what they've setup inside. It's not necessary anyway, but all knowledge is good stuff as far as I'm concerned!

In general, I find that starting with rather flat curves for everything is best for the first hovering etc. Increase the curves as your skill levels build. What you don't want is the heli zooming away when you move the sticks a bit too much in the beginning.

Try a throttle curve that comes in nice and gentle to give around 50-60% at the 50% stick point (0-25-40-50-50-50-50 for a seven point radio) then you have enough head speed to lift the heli when it gets enough pitch.
The pitch curve can be (46-48-50-55-60-62-65) so that the required pitch is coming together with the head speed in the region of 55-60% stick position. This way the heli won't go into orbit if you go a bit too far. Depending upon the model, you'll need to change the upper three points to achieve the optimum, but only use what's absolutely necessary. Maybe the highest will be up to about 75%.

My habit was snatching the stick down because the curve was just too steep with a 100% pitch as the final point, the landing gear and feather shaft took a real bashing even with training gear fitted. Aim to have the heli around waist height to start trying to stabilise the hover. If you use too much negative pitch and have a start point nearer to zero then it will just slam itself into the ground. Also not desirable.

D/R and Expo also need to be lower settings to start off with or the heli will tip on take off or tilt too much when you make corrections to a stable hover. I use 45% D/R and 35% Expo for the Aileron and 35% D/R and 35% Expo for the Elevator. This is enough for first steps towards achieving a stable hover. I've experimented with all kinds of combinations and it's possible to control with almost any (even negative Expo) figures. Try changing only in 5% steps at first and then 15% steps are a good optimum to give noticeable change to the heli reactions.

When you find the best settings for you and the model, stick with them and make sure that your practice is evenly distributed between simulator and actual field practice.

Finally, try to do the field practice during as near to perfect weather conditions as possible. You'll need more aggressive curves just to keep it hovering in stronger wind conditions. I use an application (Weather Pro) on my smart phone to help plan my field sessions. I always seek to be below a wind speed of 8km/sec and this happens to be early in the day rather than afternoon/evening where I live.

Good luck!
 

wtowns

New Member
Thanks Heaps Heliman450. That is really great info. I do appreciate all the help I can get.
I hope 2016 is a fantastic year for you and all the folk on this site.
Cheers
Warren
 

wtowns

New Member
Can anyone tell me what the servo Frequency is for the HS-5055MG, I have just swapped over to them on my 300cfx and have downloaded the chart from Hitec but I can't see anything about what the frequency is...I need to set it in my AR7200BX. It asks is it 50, 65,120 etc. Can anyone tell me or maybe how I can work it out.
Thanks in advance
Warren
 

Heliman450

Well-Known Member
Can anyone tell me what the servo Frequency is for the HS-5055MG, I have just swapped over to them on my 300cfx and have downloaded the chart from Hitec but I can't see anything about what the frequency is...I need to set it in my AR7200BX. It asks is it 50, 65,120 etc. Can anyone tell me or maybe how I can work it out.
Thanks in advance
Warren

Hi Warren, I visited Spektrumrc.com to check out their table of servo frequencies but it's not showing right now. I went there when programming my own AR7200BX. Make contact with them to find out why the pdf is missing and ask them for the exact frequency.

In the meantime, you won't damage the servo by using the default setting of 50Hz (cyclic and tail) and you can always return to update the setting at a future time or wait until you get their confirmation. My Blade 450X is using digital servos with 200Hz and 270Hz (cyclic/tail) so it's probably a similar frequency.
 
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