Difference between FB and FBL bell cranks, 120* and 140* CCPM

[Bob O]

Thought I point out something that I discovered today while continuing my build. Using the factory FBL conversion (head assembly), I pulled the elevator arm out of the box and installed it in place of the stock arm. I then got my 140* CCPM kit out and proceeded to install the bell cranks. In comparing them to the 120* bell cranks that came with the FBL conversion, the ball spacing was significantly different.

Trying to make sense of this difference, I retrieved the stock plastic bell cranks from the kit and compared them to the 140* bell cranks as well as the 120* FBL bell cranks. I found that the stock plastic bell cranks, albeit for a 120* setup, had the same ball spacing as the 140* bell cranks.

I had previously compared the stock elevator arm to the FBL arm supplied in the FBL conversion, and knew that the ball spacing on the stock arm was shorter. So in order to make the 140* bell cranks work with the FBL conversion, I had to use the stock elevator arm. Do not use the elevator arm marked "FL" if setting up the swash plate for 140* CCPM.

In checking the instruction sheet that came with the FBL conversion, it mentioned nothing of the supplied elevator arm being for use with the 120* bell cranks ONLY. In checking the heli's manual, there was no mention of this there either. If someone finds that I overlooked it, please point it out to me.

Here are some pics that show the differences between the stock plastic bell cranks and the metal FBL bell cranks, both intended for a 120* CCPM setup. Being that the 140* bell cranks were installed on the heli at the time I took the pics, they aren't included here.

If setting up the swash plate for 120* CCPM FBL, these metal arms must be used together. These are the ones supplied in the Titan X50 FBL conversion.



These two pics show the difference in ball spacing between the stock plastic bell cranks and the metal ones included in the FBL conversion kit.





Here's a pic of both elevator arms. The FBL one is on the left, the stock one on the right. You can really see how much of a difference there is with the ball spacing. If using the stock plastic bell cranks or the 140* bell cranks, use the stock elevator arm, which has no markings on it.

[Bob O]

On the topic of the MICROBEAST with 140* bell cranks on this particular heli, I just attempted a setup this morning to see how things would shape up with the balls in the closest holes on the servo wheels. The holes are 10mm from the servo's output shaft.

On setup menu point "J", I didn't get blue until 7 degrees. With 13* collective on the Extreme preset, I get the blue light easily on setup menu point "L" however.

So the logical step to get blue on point "J" is to move the balls inward on the servo wheel. I'm going to have to drill custom holes as I'm already at the innermost holes. I'm going to go 1mm in on each side and call it a day. I'm using Torq HV servos.

[johnbs8]

so im going to assume that the FBL cranks are specificly for the TT FBL head. im using a Tracx FBL (compass head) on both my helis and use the normal bells and all is fine. i did pick up a set of the TT FBL cranks for a moc up but im going to return them.

[Bob O]

Originally Posted by johnbs8

so im going to assume that the FBL cranks are specificly for the TT FBL head. im using a Tracx FBL (compass head) on both my helis and use the normal bells and all is fine. i did pick up a set of the TT FBL cranks for a moc up but im going to return them.

Well, here's my take on the FBL cranks.

Being that making the switch to FBL usually requires more resolution from the servos (less travel on the control surface end), the bell cranks in the FBL conversion were made with a wider ball spacing to provide that resolution without modifying the ball spacing on the servo arms. However, that could be taking into account using the factory conversion head.

Being that you've used the TracX head and all is fine, that definitely shows variances between designs from one manufacturer to the other. That being said, depending upon which FBL control unit you go with, you still might end up making small modifications to tweak it to perfection, depending upon what you're after and how perfect you want the setup to be.

Right now with the MICROBEAST at 140* CCPM controls, my setup isn't ideal with the servo wheel ball spacing I'm using. My heli will still fly just fine (has yet to be seen) being that the setup is only one degree away from what's ideal, but I'm still going to strive for the perfect setup because that's just me. And it's still 20*F and snowing outside.

I'm going to order some different wheels with closer ball spacing before I drill custom holes.

[Bob O]

Every wheel I've looked at has holes no closer than 10mm. So if I want to go to 9mm, they will have to be custom drilled.

So I set up the MB completely today using the holes at 10mm. I got the red LED at 6 degrees in "J", which I'll settle with for now. Thanks to sutty, knowing that a heli will fly fine with a purple LED at 6 degrees, mine should be good. It's close enough to blue (6.9 degrees) that I will be happy with it unless flying it proves it to be bad.

At setup point "L", I was easily into the blue LED without a hint of binding. During this step, while looking at the servo-to-bell crank linkage rods, I found that they were very close to contacting the center ridge around the mounting screw. That made me wonder if I did try the balls at 9mm out, I might have some unwanted interaction there.

My best bet so far as I can tell is to fly it as it is and see how she performs. Having had the MB on two other helis, I realize the blue LED at "J" isn't required. I do have one other option, and that is to change it over to a 120* swash setup, which will allow usage of the other bell cranks. That will, without a doubt, afford some flexibility with ball placement, either resulting in the blue LED at 10mm ball spacing, or at least make it so the balls can be used in holes existing further out.

I'll update this thread in a month or so when spring gets here.

[adi1893]

Im goin FBL on the x50 in a while, wondering if I can use an align 600DFC FBL head......

Thanks

[Bob O]

Originally Posted by adi1893

Im goin FBL on the x50 in a while, wondering if I can use an align 600DFC FBL head......

Thanks

It would come down to swash height, jesus bolt holes, etc. I can take some measurements for you whenever you need. Just let me know.

[adi1893]

Originally Posted by Bob O

It would come down to swash height, jesus bolt holes, etc. I can take some measurements for you whenever you need. Just let me know.

I am using the 140degree ccpm control arms, reading the thread I guess I won't need any different control arms, like the ones that come with the TT FBL head. I would like a lower cg on the x50 with the 600DFC head that's why the idea sounds good to me. Is it overall a good idea and give me better performance than the TT head? Well I'll need some help with that. Will I get enough swash travel and will there be chances of a boom strike because of the lower height of the DFC head? It looks like I will have to cut the X50 shaft smaller for the DFC head but I'm afraid of the chances of a boom strike. Any other problems I might come across....and overall will it be better than the TT FBL head?

[Bob O]

Well, I don't have any experience with the DFC head so I can't say if there will be a performance increase or not. I also can't speak of clearance issues with the DFC head. Sorry.

[adi1893]

Originally Posted by Bob O

Well, I don't have any experience with the DFC head so I can't say if there will be a performance increase or not. I also can't speak of clearance issues with the DFC head. Sorry.

Thanks for the help, could you please suggest anyone from whom I can get further clarification?

Regards.

[Bob O]

I don't know anyone using the DFC head on the X50.......sorry.

[adi1893]

Originally Posted by Bob O

I don't know anyone using the DFC head on the X50.......sorry.

I meant someone having an X50 and another heli with a DFC head.....so he/she could compare in real time and all.....neway.....

[Bob O]

Originally Posted by Bob O

Every wheel I've looked at has holes no closer than 10mm. So if I want to go to 9mm, they will have to be custom drilled. SNIP

Found some!!

http://www.readyheli.com/H1080-R-Qui...d_p_36666.html

[johnbs8]

that quick UK wheel looks aluminum. not a good idea to use metal horns.

[Bob O]

Yes, they are metal. I haven't put them on yet. I'm going to check and see how far my servos travel in their current setup before I consider changing them out.

I understand the risk in running metal wheels.

[gwright]

The longer bellcranks are as you pointed out, to give more resolution. When I first put the fbl head on I had something like well over 20 pitch either way using the 140 bellcranks and servo wheels drilled to match the 23mm spacing (11.5 on each side). I installed the fbl bellcranks and still had way too much movement, so I realized the holes needed to go in on the servo wheel. I don't like binding even if it is a tiny bit, and with the straight bellcranks and straight servo arms you'd get a touch of it at extremes, so I drew up the servo to bellcrank geometries in CAD, then determined how much movement was needed by measuring the pitch change per a given amount of bellcrank movement. I checked servo movement with the GT5 and the pitch range maxed out, which is 127 on the GT5 (don't understand the strange numerical limit, but it's just a number, doesn't really matter). Working backwards with the above date I determined that to max out resolution and allow for 14 degrees of pitch each way I needed 8mm servo arms. Then, working in cad I drew lines between an 8mm radius circle on the servo wheel(tangent to it) and the 14mm radius balls on the bellcrank. I took the reciprocal of the angle at the bellcrank and applied it to the servo wheel at 8mm distance from center. To make a short story long (g) It showed I needed .81mm offset in the servo wheel ball locations to eliminate all binding. I printed out a pattern from cad, used the undrilled futaba wheels and drilled my own holes. Perfect movement and no binding at all at the extremes and maximum resolution. Different servos, radio's, and fbl units may require a tiny bit different geometry, as not all brands of equipment move the servos that exact same amount at full throw, but this will be closer and much quicker than trial and error. I'm attaching a pdf (i hope) that has three of these wheel drawings and a little scale so if your printer doesn't scale it correctly you can scale up and down till the printed scale matches a ruler. All push/pull arrangements that are symmetrical should have the pushrods identical in length, so I'd adjust the pushrods till the ball link centers are the distance from the center of the servo wheel to the center of the bellcrank, both the same, the snap them on. If you adjust push'pull rods other than being identical you will induce binding, so I would caution against it. I think it took 3 or 4 turns "out" on both pushrods in each location.
Hope this helps.

[KouDy]

140 degrees conversion is just the bellcranks and links? There is no 140 degree swashplate?

I mean to make it work as 140 you need "just" the longer arm on bellcranks and that's it?

[gwright]

140 conversion gives you new bellcranks for the front plus longer arms for the front of the swashplate to move the balls into that position. fbl conversion gives you 120 geometry bellcranks but with longer spacing on the push/pull to gain full resolution with fbl since there is more movement in the blade grips.

going 120 to 140 only needs changing the front ball geometry on the swash, hence only the two front bellcranks and swash balls are changed. 120 versus 140 nothing changes with collective inputs, nothing changes with aileron inputs. The resoning for 140 is that it equalizes the servo movements for elevator inputs, as with 120 you need less front servo movement compared to rear servo movement for elevator inputs. 140,..or more correctly 135, changes it so that all movements are equal. The radio software(for flybarred) and the fbl controller software, correct for the inequal movements in 120 setups, hence the reason you must select 120 or 140 in the software. If you use 120 software settings for a 140 setup, or vice-versa, you end up with small collective inputs when giving elevator inputs.

[Bob O]

Wow, excellent info gw! But I can't see the attachment.

I have the new wheels with 9mm spacing but am going to try it the way it is w/ 10mm spacing.

I didn't factor any type of offset like you did, but I'm not a CAD or geometry guy either.

Thank you!!

[gwright]

yeah,.. some problem attaching pdf,.. can't get it done. Tried a few times and it keeps telling me I allready attached it in another message. If you want to PM me with an email address I'll send it to you