450 Weird swashplate movements

[Mac Mckee]

I have a 450 class heli in an RC Aerodyne MD500D fuselage. No maiden yet. Thought it was ready. Have noticed what I think is a problem. My swash servos are HiTec 65MG super feather and i am running everything with an AR7200BX. At 40% throttle at run up I observed the pitch and aileron servos quickly pitch up and move the rotor disk. Not at the same time, they kinda took turns. No rhythm to it, just random. Is this normal? Compensatory? Also, looking into the fuselage I noticed the "floor" is not level and drops to the left slightly looking towards the tail. I figured this was compensating for something, but do you level the swash to the frame or the floor? When the frame is in the fuselage and sitting on the skids the swash is crooked. Im guessing its doing that because of the floor? Is that correct? Any thoughts would be greatly appreciated!!!

 

[Smoggie]

Hi, welcome to the forum.

The swash has to be aligned perpendicular to the main shaft, ignore the bottom of the fuselage, it's irrelevant.

Servos jumping isn't normal. If the servos start jumping and/or the swash tilts as the heli spools up that probably indicates high vibrations interfering with the gyro, which must be corrected before attempting flight.

 

[Admiral]

Any attempt to take off will probably end in tears, how is the AR7200BX mounted? Check that the tail boom or tail rotor housing is not vibrating against the fuselage .

PS. Welcome to the forum.

 

[Mac Mckee]

Thanks for the welcome!!! To answer smoggie the swash is perpendicular to the mainshaft until i mount it into the fuselage on the tilted floor. (I watched a video of a 500 size md500 build and his floor was tilted also and was a different manufacturer. Not sure about the tilted floors purpose. So youre saying with it in the fuselage on the tilted floor make the swash perpendicular to mainshaft? At the 40% throttle the vibrations are very minimal. Eveything inside clears the fuselage with plenty of room. Thanks for the feedback!!!!

 

[Mac Mckee]

Also ar7200 mounted horizontal on top of tail box. I cant see where it is touching the fuselage anywhere.

 

[Mac Mckee]

After further inspection the fuselage is touching the back corner of the bx. These fuselages look great but are anything but symmetrical on the inside. I mounted the bx perfectly on the frame yet I have half an inch clearance on one side and quarter on the other. Didn't notice before. Thanks to everyone!!!!

 

[Smoggie]

Sounds like you could have the answer on the unusual servo movement!

As for the swash, it must be perpendicular to the main shaft. Any 'floor' in the fuselage or any other part of the heli come to that is irrelevant, the main shaft is the only point of reference that matters. This is why swash levelling tools fit of the main shaft.

 

[mesapilotrjguy900]

do you have a swash leveling tool?

 

[Mac Mckee]

I do. That's the weird thing. With the frame out of the fuselage it was perfectly perpendicular to the main shaft. I put it in the fuselage and powered up and swash was tilted. Scratching my head on that one. I'm traveling now and won't be back to it for a few weeks. Stepping away from it brought about some great pondering as to the problem. Few things to try when I get home. Thanks!!!

 

[mesapilotrjguy900]

no prob hope you get it figured.

 

[Smoggie]

The swash may tilt once the gyros are active. The swash can only be checked for level when in setup mode.

 

[Geena]

What kind of double side tape did you use to stick it down? If they are still supplying that thick spongy foam tape with the unit, that could be your problem. That thick tape allows the unit to pick up even the smallest vibrations, and it confuses the sensors. So if you do have that foam tape under it, try a piece of the grey 3M or Scotch indoor/outdoor mounting tape. You can get them at any home depot.

 

[S_Dave]

Hello, I'm having a similar "weird swash movement" issue but it's happening during setup. I'm using Tony's excellent video and following along with the AR7200BX manual. Everything goes smoothly until i get to the part "Setting the Swashplate Servo Directions" which is Step I. The Pitch and Elevator servos move a large amount but the Aileron servo only moves a fraction of what the others do. Here's what I've checked:
--in DX7s swash menu, all 3 servos have same value (+60)
--servos are plugged into correct channel of AR7200BX receiver
--all 3 are the same servos (new, tested okay Savox SH-1250MG)
--swash servo frequency set to 200 Hz (Savox says these are good up to 250-333 Hz)
--power is a solid 5.1VDC from a separate BEC

Thanks for any help or suggestions anyone may have. I'm looking forward to learning a lot from this forum.
Best regards,

Dave
Mikado Logo 400
P.S. safe travels to/from IRCHA for any who are going

 

[Mac Mckee]

Hello, I'm having a similar "weird swash movement" issue but it's happening during setup. I'm using Tony's excellent video and following along with the AR7200BX manual. Everything goes smoothly until i get to the part "Setting the Swashplate Servo Directions" which is Step I. The Pitch and Elevator servos move a large amount but the Aileron servo only moves a fraction of what the others do. Here's what I've checked:
--in DX7s swash menu, all 3 servos have same value (+60)
--servos are plugged into correct channel of AR7200BX receiver
--all 3 are the same servos (new, tested okay Savox SH-1250MG)
--swash servo frequency set to 200 Hz (Savox says these are good up to 250-333 Hz)
--power is a solid 5.1VDC from a separate BEC

Thanks for any help or suggestions anyone may have. I'm looking forward to learning a lot from this forum.
Best regards,

Dave
Mikado Logo 400
P.S. safe travels to/from IRCHA for any who are going

You can't have any mixing in your transmitter. You need a blank profile for a helicopter, select swash style, and you may need to reverse some servos in transmitter menu--that's it. Everything else is done by receiver. My servo jumping is on run up and caused by some vibes being picked up by an unknown source. Good luck.

 

[Mac Mckee]

What kind of double side tape did you use to stick it down? If they are still supplying that thick spongy foam tape with the unit, that could be your problem. That thick tape allows the unit to pick up even the smallest vibrations, and it confuses the sensors. So if you do have that foam tape under it, try a piece of the grey 3M or Scotch indoor/outdoor mounting tape. You can get them at any home depot.

The double sided tape was supplied and is at least 1/4 in thick. Honestly I don't know what else to do. All blades are balanced, vibration is very minimal at 40-45% throttle where the servo "twitching" occurs. It's not just one servo, they all take turns doing it. There is not one place I can find where the frame is even close to contacting the fuselage and I've tried every tip to eliminate vibrations. Ill try the tape and see what happens.

 

[D.O.G.]

Have you check the main shaft to see if there is any nicks? You can tried erasing the AR and starting over? Sometimes it works. With that 3-M tape Geena mention is wonderful stuff to use. Shoot I think even Walmart carries it. Hope that can help.

 

[Mac Mckee]

What kind of double side tape did you use to stick it down? If they are still supplying that thick spongy foam tape with the unit, that could be your problem. That thick tape allows the unit to pick up even the smallest vibrations, and it confuses the sensors. So if you do have that foam tape under it, try a piece of the grey 3M or Scotch indoor/outdoor mounting tape. You can get them at any home depot.

After all the b.s. over the past couple of weeks putting up with "twitchy servo syndrome", it came down to the double sided tape that SPEKTRUM supplied with my BX receiver. I changed to an approx 2 mil thickness and have been running it on and off for half hour and no twitching to report. A few checks and it's finally ready to maiden. Thanks D.O.G.!!!!!!!!

 

[Mac Mckee]

What kind of double side tape did you use to stick it down? If they are still supplying that thick spongy foam tape with the unit, that could be your problem. That thick tape allows the unit to pick up even the smallest vibrations, and it confuses the sensors. So if you do have that foam tape under it, try a piece of the grey 3M or Scotch indoor/outdoor mounting tape. You can get them at any home depot.

Thanks Geena!!!!!! Switched to a 2 mil double sided tape and it works perfectly now!!!! I've been chasing this problem for 2 weeks. Thanks again so much!!!!

 

[Mac Mckee]

Hello, I'm having a similar "weird swash movement" issue but it's happening during setup. I'm using Tony's excellent video and following along with the AR7200BX manual. Everything goes smoothly until i get to the part "Setting the Swashplate Servo Directions" which is Step I. The Pitch and Elevator servos move a large amount but the Aileron servo only moves a fraction of what the others do. Here's what I've checked:
--in DX7s swash menu, all 3 servos have same value (+60)
--servos are plugged into correct channel of AR7200BX receiver
--all 3 are the same servos (new, tested okay Savox SH-1250MG)
--swash servo frequency set to 200 Hz (Savox says these are good up to 250-333 Hz)
--power is a solid 5.1VDC from a separate BEC

Thanks for any help or suggestions anyone may have. I'm looking forward to learning a lot from this forum.
Best regards,

Dave
Mikado Logo 400
P.S. safe travels to/from IRCHA for any who are going

Also I found it to be common that one servo may have a reduced throw while in that part of the setup menu, depending on which servo/direction is selected. Start with the first setting and reverse each servo in the transmitter, returning the servos to their original setting when no difference is made. Move through each selection using the rudder stick until a combo is found that works. Remember, this is only setting servo direction for collective, so incorrect cyclic response doesn't matter right now. The AR7200BX is a nice platform, but if things aren't right mechanically nothing else matters. I've been installing it in a scale fuselage so it's been a REAL treat to acquire proper fitment, vibration reduction, and performance. When there was a problem, I found it was usually solved pretty simply with a little thinking. There was always a solution. I was handling mine a good bit fitting it and most recently the tail somehow got put into heading lock mode and for some reason had a reduced throw on the tail rotor. It would try to spin with torque even with full rudder authority. Considering I had to assign the gear channel to the gyro to get it back to normal rate leaves me dumbfounded as to how it changed to begin with. My point is check and double check everything. Good luck asnd I'll try to answer any questions although it seems that there are some very knowledgeable folks on here so an answer shouldn't be hard to come by.

 

[S_Dave]

You can't have any mixing in your transmitter. You need a blank profile for a helicopter, select swash style, and you may need to reverse some servos in transmitter menu--that's it. Everything else is done by receiver. My servo jumping is on run up and caused by some vibes being picked up by an unknown source. Good luck.

Thanks for the reply. Your "no mixing " helped. I had wrongly selected a 120 deg swash in the first step. Instructions clearly said to use 1-servo Normal. Changed that and the setup is proceeding nicely.
"Tango Mike!" (Green speak for "thanks a million!"
V/r
Dave