IMAC Dalton 300 ml build thread.

[orthobird]

Put in 5 more flights this past weekend, and with the change i made to the wing tube, there was no change in the symptoms. I also turned her on and idled her, and once the vibrations started, I did the palpation test, and could not stop the sound with pressing on all parts of the airplane.

Once I brought her home, I was finally able to get time to remove the cowl/baffles, and inspect. Could not find any problems with the motor mounts, but i went ahead and removed the SWB standoffs, and I installed the original plywood mount that i had constructed. The holes are re-inforced with a brass tube. I also sanded the block down to give it some increased right thrust. maybe about 1 degree or so.

Now, I have to test it.

When I was at Sherman for the judging school, i was fortunate to get help from Dan Baker, an Unlimited pilot.
I was told i need to increase the aileron throw for a cleaner and crisper snap.

Therefore, I went ahead and changed the servo hole from the innermost, to the 3rd hole out. Now my full aileron defection went from 2" to 3".

One last modification I made was for the plug ins to the wing. I am using the Taildragger RC 2 in 1 servo leads, where you can connect two wing servos and use a single MPX plug. Before, I would connect the wing servos to the adaptor, and velcro them in.
Now, these plug into the frame, and they have a clip to prevent them from backing out. They are quite firm inside there.

All I have to do now is paint the block they are installed on.

 

[orthobird]

Here are some pictures taken on my airplane flying!
Pretty darn good photographer who took the pictures, credits to Rich Whitlow from Baton Rouge.

 

[Capt.Roll]

Plane looks great Ortho.........Rich seems to have a very good perspective when using his camera. I'm not sure if I've seen any of this photos that weren't good.

 

[Dirt Doctor]

I have had planes that had a vibration sound in them and after much hair pulling and gnashing of teeth several of us determined that the sound was coming from the fuse covering. The covering was acting like a drum at certain speeds which apparently has certain frequencies hence the sound! That may be what is happening to your plane.

 

[orthobird]

I did not check that Bobby. Good idea. I will check the areas that are not sheeted to see if that is the source of the vibrations. it does sound like a drum!

 

[orthobird]

Here is a picture with the block painted....

 

[orthobird]

great news!! that vibration, which was at low rpm's, is now gone. This was fixed when i removed the standoffs and installed the plywood mount, which has a greater surface area for the motor mount of the engine onto the firewall.

 

[BalsaDust]

Good to hear.

 

[fencelake]

great news!! that vibration, which was at low rpm's, is now gone. This was fixed when i removed the standoffs and installed the plywood mount, which has a greater surface area for the motor mount of the engine onto the firewall.

That's good news!! I've seen that recommendation for my engine as well (DA-120). It's brand new, so there's going to be vibration... so I'm going to wait a little while, but it's really supposed to help.

 

[orthobird]

yep, even twins, in my opinion, should not use standoffs, no matter what the size.
for 50 cc and under, might be ok, but for anything bigger, standoffs are less able to dampen the vibrations of a 2 stroke.