700 My New T-Rex 700X Build
- Thread starter Heliman450
- Start date
Heliman450
Well-Known Member
Hi Steve, yes I've got that clearly fixed in. It seems to be that the tail push rod is too short. What did you have as the centre to centre length. Knowing that will help me quickly zero in on a measurement and work from there.
Heliman450
Well-Known Member
At the moment, it's set for -26 to get zero degrees on the tail and the rod is 80.5 cm centre to centre. I think I'll be looking for another solution before trying to fly it.
Heliman450
Well-Known Member
Cheers Steve, good to see the photo before setting off for my workshop. I also experimented a bit with the servo arm position on the splines and then the sub trim. In both cases the position of the arm is almost identical. Looks like Align messed up on their measurements somewhere.
I'll let you know how I get on.
I'll let you know how I get on.
Heliman450
Well-Known Member
Hi all,
I decided to go for making a new tail control push rod so here are some photos.
#1
#2 
#3 
#4 
#5 
#6
#7 
#8 
So this is the almost finished article ready for gluing the ends to the shaft. It needed to be 80.7cm to give the blades in alignment without any sub trim to offset the servo arm.
Bye for now!
I decided to go for making a new tail control push rod so here are some photos.
#1
#2 #3 #4 #5 #6
#7 #8 So this is the almost finished article ready for gluing the ends to the shaft. It needed to be 80.7cm to give the blades in alignment without any sub trim to offset the servo arm.
Bye for now!
Last edited:
Smoggie
Well-Known Member
Phil,
You shamed me into doing the job on my pushrod right rather than relying on the workaround of the offset servo arm. The way I did it was heat up the threaded rod at the end of the pushrod with a soldering iron then once they get hot the glue holding them in softens and they pull out easily. clean up the glue residue and epoxy back in place but leave them sticking out a little further. I used your 807mm dimension as a target length, thanks!
You shamed me into doing the job on my pushrod right rather than relying on the workaround of the offset servo arm. The way I did it was heat up the threaded rod at the end of the pushrod with a soldering iron then once they get hot the glue holding them in softens and they pull out easily. clean up the glue residue and epoxy back in place but leave them sticking out a little further. I used your 807mm dimension as a target length, thanks!
Heliman450
Well-Known Member
Hi Steve, I'm impressed that you just got to it and my measurement worked OK for you, too.
We were off to a concert so I skimped a bit on the explanation. I bought the carbon tube and the ends from my local hobby shop. Gabelkopf Klebehülse ALU M3 / Stäbe 5mm 5St - Anlenkung-Teile - Scamora Webshop and I decided to add some more to my bits and pieces box. I got a 5 mm dia tube and a 6 mm. The ends are in packs of 5 and I got packs of M3 for 5 and 6 mm tube and a 2.5 mm option for 5 mm tube. The advantage was that the threaded ends are 13 mm and would work well in combination with your longer ball links. I had a total of 11 full turns to screw the standard links in fully. As the fit wasn't so great, I used some PTFE tape and worked on the basis of 5 full turns to establish the completed length. This gives me 6 more on each end to adjust for any right pitch I want to set.
The only thing that I'm missing out on at the moment is the aluminium sleeve but I don't think that's a great problem. If there's any sign of wear in future, I'm sure I can sort something out.
Heliman450
Well-Known Member
Hi all,
The push rod ends are now glued on and the adjustment checked out for being able to set a 10 degrees offset if needed. There are 5 full turns either end and it takes 3 more to get 10 mm tip to tip (10 degrees with a protractor ).
Tomorrow is Axon programming day and hopefully all that's needed in the DC-14, too. Maiden? I hear Steve asking............ probably not tomorrow but I'll do a video when I achieve it
The push rod ends are now glued on and the adjustment checked out for being able to set a 10 degrees offset if needed. There are 5 full turns either end and it takes 3 more to get 10 mm tip to tip (10 degrees with a protractor ).
Tomorrow is Axon programming day and hopefully all that's needed in the DC-14, too. Maiden? I hear Steve asking............ probably not tomorrow but I'll do a video when I achieve it
Smoggie
Well-Known Member
Good to hear it's all progressing nicely Phil. I got another couple of flights in with mine today. I cant say that the new pushrod made any noticable difference in flight but it's good to have the ball links screwed all the way onto the threads rather than only being engaged by a few turns, I'd hate for them to pull out.
Phil, on the subject of the metal tube that is missing from your new pushrod. On one of my helis heatshrink is used for the same purpose, it works fine and stops the pushrod rattling around in the guide.
Phil, on the subject of the metal tube that is missing from your new pushrod. On one of my helis heatshrink is used for the same purpose, it works fine and stops the pushrod rattling around in the guide.
Smoggie
Well-Known Member
Phil,
i've done some more digging into the short pushrod problem. The problem is that the pushrod should be 766mm long measured between the outer ends of the metal ferrules, this is stated on page 20 of the manual. The one supplied in the kit is only 760mm long. The one supplied appears to be the rod intended for the previous 700L model (part # H70073AT).
I found the total length that worked for me was 802mm centre of ball to centre of ball which is what's stated in the manual. Phil, if yours needed to be 807mm then best check that the tail boom is fully pushed into the housing. It needs to slide in far enough so that the hole in the side of the boom lines up with the locating screw hole in the right hand side of the boom mount.
i've done some more digging into the short pushrod problem. The problem is that the pushrod should be 766mm long measured between the outer ends of the metal ferrules, this is stated on page 20 of the manual. The one supplied in the kit is only 760mm long. The one supplied appears to be the rod intended for the previous 700L model (part # H70073AT).
I found the total length that worked for me was 802mm centre of ball to centre of ball which is what's stated in the manual. Phil, if yours needed to be 807mm then best check that the tail boom is fully pushed into the housing. It needs to slide in far enough so that the hole in the side of the boom lines up with the locating screw hole in the right hand side of the boom mount.
fran11784
Goblin 380 Supporter
Hi gents, just reading some of the thread. I think my kit was one of the first batch's. I didn't have any issue with tail push rod lengths. Interesting to hear. Been flying mine for a couple of months. Fly's great. I did have push rod length problems with other Align kits however.
Tony.
Tony.
Heliman450
Well-Known Member
Hi guys,
Just got home from a successful day in the workshop and from collecting my good lady from her Sunday out. I think all's ready to go but first I've got a couple of questions for Joachim at B.D. about the Axon setup process. I took loads of screen shots and photos but now I need to spend some time sorting them out. Regarding the tail push rod......
I had 807 mm to achieve a neutral pitch on the tail rotor blades and 802 mm when adjusting for the 10 mm tip-2-tip measurement they quote in the instructions. The Axon setup says to adjust it to zero, so I backed it off. Steve, I'm pretty sure that the tail boom is fully into its housing but I'll double check to be sure before I fit the locating screw. I didn't do any amount of researching where the possible error occurred but it's always possible that someone picked up the wrong one without realising that there's a slight difference. I can imagine them asking the apprentice to go get the next batch of push rods and some 'fork 'andles' at the same time
(probably not too many viewers will get that one, hey Steve??).
I put some heat shrink on the push rod as suggested and then ended up having to make some changes to the holding clip and put some tape around the tail boom to stop the rod sticking as I used 6 mm tube instead of 5 mm.
I'll do some work on the photos etc. and probably put something in a thread a bit later on. Off to eat now, I'm starving!
Just got home from a successful day in the workshop and from collecting my good lady from her Sunday out. I think all's ready to go but first I've got a couple of questions for Joachim at B.D. about the Axon setup process. I took loads of screen shots and photos but now I need to spend some time sorting them out. Regarding the tail push rod......
I had 807 mm to achieve a neutral pitch on the tail rotor blades and 802 mm when adjusting for the 10 mm tip-2-tip measurement they quote in the instructions. The Axon setup says to adjust it to zero, so I backed it off. Steve, I'm pretty sure that the tail boom is fully into its housing but I'll double check to be sure before I fit the locating screw. I didn't do any amount of researching where the possible error occurred but it's always possible that someone picked up the wrong one without realising that there's a slight difference. I can imagine them asking the apprentice to go get the next batch of push rods and some 'fork 'andles' at the same time
(probably not too many viewers will get that one, hey Steve??).I put some heat shrink on the push rod as suggested and then ended up having to make some changes to the holding clip and put some tape around the tail boom to stop the rod sticking as I used 6 mm tube instead of 5 mm.
I'll do some work on the photos etc. and probably put something in a thread a bit later on. Off to eat now, I'm starving!
Heliman450
Well-Known Member
Hi again, steaks are smelling great but the sides of veg. aren't ready yet, here are a few photos ............
#1
This photo shows the alignment markers coming together, left side completed. I hit a slight problem here after lining up the two blades, I stepped back to admire my handiwork only to notice that the washout arms weren't level. Oops (or words to that effect). I needed to increase the length of all three swash plate link rods to bring them level. All ended up exactly 51.37 mm. Of course, I needed to reset the pitch link rods to get them right again. Then came problem #2.......... The markers don't give exact alignment at zero and to my old eyes they looked identical. I needed to use the digital pitch gauge to eventually get it right and during this time made quite a change to the link rod lengths. They ended up reducing from 58.21 mm to 47.44 mm and I didn't really notice any significant change in the markers!
I also did some experimenting with the rotor blades at different positions to see how variable the measurements are at the four different right angles. Final solution was best to zero the digital pitch gauge with the tail (blade out to the left side). I took 4 sets of readings for each blade in each of the four positions but won't list them all here.
#2
#3 
#4 
The sequence above shows how I line up the blades to be correct for chord balance (usually at the field). #2 shows the link disconnected and the blade sitting balanced without any support. It only needs very slight movement for it to tip either way. #3/4 shows the blades with one balanced followed by two balanced. You can see how the far blade is off to the right compared to the shot in #4. I didn't take the photos using a tripod, but it's still possible to see the difference. I did this just to show how easy it is to be out. Previously, they looked straight without doing this step.
#1
This photo shows the alignment markers coming together, left side completed. I hit a slight problem here after lining up the two blades, I stepped back to admire my handiwork only to notice that the washout arms weren't level. Oops (or words to that effect). I needed to increase the length of all three swash plate link rods to bring them level. All ended up exactly 51.37 mm. Of course, I needed to reset the pitch link rods to get them right again. Then came problem #2.......... The markers don't give exact alignment at zero and to my old eyes they looked identical. I needed to use the digital pitch gauge to eventually get it right and during this time made quite a change to the link rod lengths. They ended up reducing from 58.21 mm to 47.44 mm and I didn't really notice any significant change in the markers!
I also did some experimenting with the rotor blades at different positions to see how variable the measurements are at the four different right angles. Final solution was best to zero the digital pitch gauge with the tail (blade out to the left side). I took 4 sets of readings for each blade in each of the four positions but won't list them all here.
#2
#3 #4 The sequence above shows how I line up the blades to be correct for chord balance (usually at the field). #2 shows the link disconnected and the blade sitting balanced without any support. It only needs very slight movement for it to tip either way. #3/4 shows the blades with one balanced followed by two balanced. You can see how the far blade is off to the right compared to the shot in #4. I didn't take the photos using a tripod, but it's still possible to see the difference. I did this just to show how easy it is to be out. Previously, they looked straight without doing this step.
Heliman450
Well-Known Member
Hi Tony, when I first noticed a discrepancy, I measured mine using a metal reel tape and hooked the end over the servo arm then deducted 3 mm to get the approximate centre to centre measurement. I didn't need to remove the rod.
Smoggie
Well-Known Member
The problem is that the thread is quite short. Mine were similar to yours maybe just slightly further out but when i checked how many turns of thread were actually engaged i found it was only three turns. I wasnt happy with that, hence why i first offset the arm then eventually pulled out the threaded rods.