Shop our Airplanes Products Drone Products Sales
Thread Tools
Dec 07, 2012, 09:38 PM
Registered User

Gyro Tests (XM Hobbies 401B Gyro) Will add more as time permits

Ive had this in my spare parts box for some time , got it VIA Ebay and it was bundled with a 9257 servo ...

Pictures show the Gyro and my 9x settings for the Video ..

This gyro was insanely simple to set up [ some times they can be a real bear ] and

Hang on - for the Noobs out there [ thats me ] , lets go through the steps one by one .

First - install the gyro to the heli [ I use double sided foam tape from my local thrift store ]

Next - plug in the gyro lead and signal leads .. Gyro lead had 3 wires and goes to channel 4 and signal wire is single wire and goes to channel 5 ..

Now you can plug in your servo lead .. Now is important to check , the little switch to see if your DS [ digital servo ] switch is on or off , if your running an analog servo , make sure its off ..

Now your ready to test on the floor less main rotor blades [ see video ]

Now should your heli spin out of control , just look at the other little switch on the gyro , it reverses the direction of the tail servo , you want to use this to change the direction of the servo .

Back to the Gyro :

Now the connectors [ to the receiver ] on both the gyro and signal leads were a bit of a lose fit for my 9x receiver [ falling out lose ] and something needed to be done about this [ slight mod to expand the plugs for a more snug fit ] .

Last thing you want when flying is for the Gyro connections to fall out while flying .

Well , VIA transmitter I just backed off sensitivity until the tail wag went away , and the video is shot with the final Tx settings [ also pictured ]

401B Gyro test (1 min 34 sec)

Now , its currently blowing a Northerly gale outside + its HOT , too hot to stress electronics .. Hopefully tomorrow will be cooler and no gale force breeze , so I can actually flight test the gyro ..

But so far on the floor , it behaves very nice ...


Its still blowing a gale out there , but I took the heli out to see if the gyro behaves , and it did alright , the conditions were some what horrific as the wind is really blowing through , so could there be better conditions for testing ? At least I wasnt correcting the tail all the time , it actually held . But I was fighting the wind and there was little if any respite from trying to keep the heli from crashing .

I did have to back of the gyro gain a little more as there was a small amount of tail wag , so depending on rotor head speed , it may need to come down some more .. I started with 41 , and backed it off to 37 it may need to come down to 35 .. Bottom line is , the gyro works , which is always nice to see .. Next Im going to re-examine the HobbyKing 401B , which didnt work at all with another Tx .


Normal - or Rate Mode !

The wind was down this morning [ small window as we are expecting high winds this afternoon ] so after testing the HK401B , I put this one back for some calm weather testing .. It does hold the tail well , but much like the HK version there is some bounce back if implementing the rudder gently , not quite as much as the HK version [ of the 401 ] but enough to be annoying . So you need to be a little aggressive with the rudder input to get the gyro to hold , otherwise if your to gentle it drifts back towards where you started [ I call it bounce back ]

There you go .. AVCS next

Much the same as the HK gyro - Wags its brains out .. and just goes crazy ..
Wow - you better like Rate mode - cos its not doing it in Head Hold mode ..
Last edited by old4570; Dec 10, 2012 at 11:18 PM.
Sign up now
to remove ads between posts
Dec 08, 2012, 05:40 PM
Registered User

HobbyKing 401B Gyro

Another Gyro from my parts box , now I did try to use this gyro a few months ago with my FS-CT6B and all it did [ the gyro ] was wag the tail insanely , I just could not stop the tail waging .. I get the feeling the HK401B wants a more complicated or featured transmitter .

Since I have some time on my hands , I fitted the gyro to my Carbon Metal heli , servo is a 9650 , Tx @ Turnigy 9x , and using pretty much the exact same settings as with the previous 401B gyro , it worked ! No insane tail waging . Go figure hu ?

So obviously , this Gyro is some what dependent on what Tx you are using , as it works with one , and not with another . Kind of might explain why some people like this Gyro , and others hate it [ for tail waging ] .

Now with the little twisty pots , Delay is set to 0 and limit is set to 110 ..

If you increase delay , it will slow the tail servo down - so if its insanely fast [ tail reacts to Tx input to quickly for you ] just increase Delay to slow things down ..

This controls servo travel , so check to see if there is over travel at each extremity of stick movement , and if there is just back of Limit to a lower number to literally limit servo travel ..

Again the two small switches DS and DR [ DS digital servo - DR direction ] .. If your using an analog servo make sure DS is off and if your helicopter spins uncontrollably reverse the DR switch ..

HK401B (1 min 40 sec)

Now it is a really Gale force Breezy day out there , and I was hoping to get through more Gyros today , but its literally dangerously windy out there , and test flying the HK401B - I nearly lost it when a the wind suddenly picked up a lot of speed and picked up the heli and almost carried it away .. Even @ almost 0 throttle the heli kept rising , and even hovered for about 5 seconds @ almost 0 throttle .. I was able to salvage the situation , land the heli , and call it a day ! Its a good day when you dont bend it like Beckham !

The gyro held the tail rather well , unfortunately , no meaningful tests could be done as 100% of the time was spent trying to maintain control of the heli .. [ Damn its been a windy year this year - I dont ever remember it being this windy ]


Normal - or Rate Mode

Wind was down this morning :

Ok the gyro does hold the tail well , not much issue here , what I didnt like was if you turn the tail too slowly , the gyro has a tendency to bounce back about half way , does this whether you go left or right rudder ..
Too gently and it does the bounce back ..
If your more aggressive with the rudder then it holds position rather well ...
I did vary the rotor head speed a fair bit to see if its related to head speed - but no .

Next AVCS mode

Or head hold or Head lock mode :

Now I did mention this gyro is known for tail waging like a lost dog : yes
And thats what it did , aaah yes , There was no controlling it in AVCS , none what so ever ...
In fact it wagged so hard it tipped over the heli some 6 times , last one was the charm , stripped a cyclic servo .. Wonderful !
So if you get one , and it wags nuts on you , try normal mode [ rate ] , at least that way you get to fly .

Not a flash gyro at all in HH mode , do you really want to buy a gyro thats a pig !

I have to rate this one a pig in a poke .
Last edited by old4570; Dec 10, 2012 at 09:56 PM.
Dec 09, 2012, 07:51 AM
Registered User
Wow, great vids. This January when things slow down I'm going to sell my Esky CPX for parts and work on my 450 clone with the HK401 and get it to fly. Then I can build my Align 450. I'm hoping the servo reverse is my problem. I can't get mine to respond like in the video. This is mine:

HK401B gyro need help setting up (1 min 48 sec)
Dec 09, 2012, 04:19 PM
Registered User


Originally Posted by shahram72
Wow, great vids. This January when things slow down I'm going to sell my Esky CPX for parts and work on my 450 clone with the HK401 and get it to fly. Then I can build my Align 450. I'm hoping the servo reverse is my problem. I can't get mine to respond like in the video. This is mine:
Wow ! thats not so great ..
What Tx are you using ?

Could be Tx settings , could be the servo , could be the gyro ..

So we need to isolate the problem .. First make sure the servo works , so bye pass the gyro .. Just check to see if the servo works less gyro .

Gyro , make sure all the settings are good .. Trim pots are set to maximum ..

So delay to 0 fully anticlockwise , Limit fully to 120% [ clockwise ] and make sure the little dip switch for servo type is OFF for analog or you may fry the tail servo .
Dec 09, 2012, 07:56 PM
Got Helis
choppersrule's Avatar
+1 with what Old4570 said.. Plus I noticed that both of your tail servo rod guides are loose and moving back and forth, while you were testing.
Dec 09, 2012, 08:13 PM
Registered User
Originally Posted by choppersrule
+1 with what Old4570 said.. Plus I noticed that both of your tail servo rod guides are loose and moving back and forth, while you were testing.
Yeah, that's how they are. How do I tighten them? And, I am using a Turnigy 9x as well.
Dec 09, 2012, 08:51 PM
Got Helis
choppersrule's Avatar
If there's enough room, you can wedge a small piece of zip tie inbetween the boom and the guide, or even a tooth pick. Another option would be to use some CA glue / super glue.

On your problem, put the gyro into 'Rate' mode and move your rudder stick back and forth to full extent. Watch the servo and the tail slider to see if you have full deflection.
Dec 10, 2012, 04:03 PM
Registered User
Updated with some more flight [ calm conditions ] time observations
Dec 10, 2012, 09:58 PM
Registered User

Sorry Guys

I should wait to post : But such a backlog of things to do .

The Christmas rush !
Dec 11, 2012, 12:24 AM
Registered User

Detrum GY48V

Nor (0 min 47 sec)

Gyro in Norm Mode [ Rate ] Tx set to 70 [ Gyro sens ]

Not bad , a little bit of bounce back when you gently apply rudder [ comes back some what in the direction you started from ]
Other wise does the job better than the 401B gyros ..

Head lock (0 min 50 sec)

Gyro in AVCS [ Head Hold ] mode . Tx set to 50 [ Gyro sens ]

Well here we have a gyro that actually works in HH mode , and it works rather well , no bounce back [ does not return towards starting point when applying rudder input ]
Gyro does a decent job of holding direction .. Which ever mode your in .

I would rate this as a functioning Gyro - Not bad for the money !

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
For Sale Typhoon 2216,HOBBY KING HK 401B gyro,HK 10AMP Esc tech69x Aircraft - Electric - Helis (FS/W) 0 Oct 15, 2012 10:28 PM
Sold Hobby King 401B gyro(s) x3 Depron Dave Aircraft - Electric - Helis (FS/W) 2 Aug 25, 2012 10:02 PM
Sold Hobby King 401B gyro(s) x3 Depron Dave Aircraft - Electric - Multirotor (FS/W) 0 Aug 25, 2012 08:20 PM
Sold xm Hobbies 401b Gyro captainpitts Aircraft - Electric - Helis (FS/W) 1 Mar 31, 2011 09:40 PM
Wanted xm hobbies 401b gyro kremecheze Aircraft - Electric - Helis (FS/W) 3 Oct 26, 2009 09:25 AM