Author Topic: Line length for 3 line systems (Read 597 times)

Jim Oliver · « **on:** August 30, 2009, 12:11:56 PM »

When making up lines for the Brodak 3 line system, how important is it to have all three line the exact same length----what is a reasonable tolerance?

Thanks,
Jim

skyshark58 · « **Reply #1 on:** August 30, 2009, 01:21:37 PM »

Very important! Also dedicate a set of lines and clips to each airplane you build. Once you have everything rigged you don't want to start the process over again on another model. Trying to save a buck and have one set of lines for many models only adds time and increases frustration in the long run.

Jim Oliver · « **Reply #2 on:** August 30, 2009, 02:14:52 PM »

I have line/handle sets for my aerobatic models, as you suggest, so I understand the concept.

Wondering about the degree of precision required for the Brodak 3 line system........any numbers you could provide?
I think I can get the line length the same within 1/8 inch, is that close enough?

Thanks,
Jim

Clancy Arnold · « **Reply #3 on:** August 30, 2009, 03:45:16 PM »

Jim
Read the instructions!!!
I only fly Electronic throttle, but as I look at the handles the lines appear that they are NOT the same length. Especially the throttle line.

Gentlemen am I wrong?

Clancy

Mike Anderson · « **Reply #4 on:** August 30, 2009, 04:03:30 PM »

I guess the ideal is to have the handle match the leadouts (ie - since the throttle lead on the handle is short, then the throttle LEADOUT should be long -). If the handle leads match the leadouts, your lines would need to be all the same length.

In the real world, however, that would require three precision lines. It is far easier to have a set of lines that stay with the plane they were made for, as detailed on other threads. Then you can use different length line connectors to fine tune them. I actually go to the trouble of setting up each plane for a particular handle, and then marking on the wing tip WHICH handle to use with each.

It really comes down to getting the two elevation lines about the same, so that you can fly with the elevator as neutral as possible (because the handle has no way to adjust any of the lines) and getting the throttle line to move the throttle through its complete range - if it is too long or too short, you will not be able to get all the way to full throttle or all the way to full idle (one or the other).

That is why the advice is give to not mix J Roberts handles with LR/Brodak bellcranks or vice-verse - the throttle movement available from the handle does not match the movement range of the bellcrank.

Bob Heywood · « **Reply #5 on:** August 30, 2009, 06:09:54 PM »

Jim,

I would peg the allowable tolerance @ +/- 1/32" for the lines. I know that's tight but if not the system does not work right. All three lines are intended to be load bearing. My technique is to make up one end on all three and put on a pin to hold even. Stretch all tight at the same time and make the first bend at the other end simultaneously.

If the power line is too long only the control lines will bear the flight load at high speed and the throttle will have a dead band until you have control. If the power line is too short the bellcrank will begin the travel along the slot and reduce available throttle movement. With all this in mind it is important to make all final throttle travel adjustments with the complete system; plane, lines, and handle.

Also, be very careful to offset the leadouts equal to the Brodak handle. In conventional High Speed position (trigger pulled back) the control leads are 2-1/16" longer than the power lead. The plane leadouts need to mirror this dimension, that is, the power leadout needs to be 2-1/16" longer than the control leadouts when in neutral. Note of Caution - the Brodak instructions for the handle list the wrong dimension. They use the old J. Roberts number.

I have been caught a couple of times and had to do the line clip shuffle to get things to work. Rather not have to do.

Hope this helps.

Bob Heywood
Dayton, OH

john e. holliday · « **Reply #6 on:** August 31, 2009, 08:07:07 AM »

As stated one set of lines for each airplane. You can get by with one handle. Make up your lines on the airplane with the handle. Now if you change handles things will be different.

Another thing a well known carrier flyer used the trigger forward for high speed. Claimed he get better results with it. Have fun, DOC Holliday

Author Topic: Line length for 3 line systems (Read 597 times)

Jim Oliver

Line length for 3 line systems

skyshark58

Re: Line length for 3 line systems

Jim Oliver

Re: Line length for 3 line systems

Clancy Arnold

Re: Line length for 3 line systems

Mike Anderson

Re: Line length for 3 line systems

Bob Heywood

Re: Line length for 3 line systems

john e. holliday

Re: Line length for 3 line systems