Author Topic: J-Roberts Handle with Brodak Belcrank (Read 795 times)

Bob Reeves · « **on:** July 22, 2010, 01:54:45 AM »

OK I know the two shouldn't be mixed because the control throws are different... BUT... Someone gave me a like new J-Roberts handle and figure the odds of finding a J-Roberts bellcrank are pretty slim. I would like to use the handle on a .15 size FJ4 (still in the planning stage) with a short span Brodak bellcrank.

Doesn't the Brodak system have a longer throw than the J-Roberts? If this is the case I wouldn't think one would have a big problem other than not being able to get the full range of the bellcrank. Thinking the range issue can be compensated for (if even necessary) in my crossover linkage between the bellcrank and throttle.

So tell me what's wrong with my logic?

Paul Smith · « **Reply #1 on:** July 22, 2010, 05:59:02 AM »

I agree. I mix the handles and bellcranks and think nothing of it.

I some cases I use a reversing/reducing bellcrank to make it right.

The really critical thing is matching the throttle rod throw to the throttle arm on the carb, otherwise, you might be transmitting the entire line pull to the carb. In addition to the reducing bellcrank, a longer throttle arm can get this done.

This issue is similar to two line control line systems that are rigged to "bottom out" the throw at the elevator horn, then the builder blames the clevis when it fails while being loaded with the full line pull.

At this point I will save Clancy a shameless plugging post by mentioning that you could solve this issue by buying an electronic system from him.

john e. holliday · « **Reply #2 on:** July 22, 2010, 08:33:19 AM »

I too still use my J-Roberts handle no matter what ever bellcrank system is in the plane. Just make sure that the load is equal on high speed. The Brodak handles I have I had to do a lot of work to get them to work smoothly. And yes Clancy's electronic system is viable, but, you need larger lines.

Bob Reeves · « **Reply #3 on:** July 22, 2010, 11:31:17 AM »

Thanks for confirming my thoughts..

Spent my whole working life messing with electronic gigits and now only play with electrons when I have to. Only thing that might spur my intrest is if the CL rules makers would endorse spread spectrum technology.

john e. holliday · « **Reply #4 on:** July 22, 2010, 08:55:57 PM »

Tha would open a whole new can of worms. I even lke the idea the guy came up with. It would work in scale competition also. If they can have a hundred radio planes in the air at one time, what would it hurt to use it in control line to control other functions. But, the elevation must be controlled by the handle and elevator.

don Burke · « **Reply #5 on:** July 23, 2010, 03:26:59 PM »

Ditto on making sure that the throttle line doesn't take all the load, bad scene if it happens.

I think the only can of worms opened would be that involving getting a rules change through.

Bob Heywood · « **Reply #6 on:** July 24, 2010, 09:33:38 PM »

I would move cautiously on this one. The line tension will only equalize at one discrete point over the total range of travel.

I have a brand new Roberts Upright unit that is yours, on the house. PM me your address.

Bob Heywood
Dayton, OH

Bob Reeves · « **Reply #7 on:** July 25, 2010, 06:06:59 AM »

Quote from: Bob Heywood on July 24, 2010, 09:33:38 PM

I would move cautiously on this one. The line tension will only equalize at one discrete point over the total range of travel.

I have a brand new Roberts Upright unit that is yours, on the house. PM me your address.

Bob Heywood
Dayton, OH

Boy, can't beat a deal like that.. PM on the way, thanks.

Melvin Schuette · « **Reply #8 on:** July 25, 2010, 05:46:51 PM »

Bob,

You are correct the Brodak belcrank can does have a longer throw then the J Roberts, but you can use it with a J Roberts handle without a problem. Where you notice the difference is when you move the throttle back and forth how much the rpm increases or decreases per the amount of travel of the throttle at the handle. On thing I suggest is that if you do not have to move the throttle all the way from the front to the back at the handle to get the carburator to open and close fully, then lengthen the throttle arm on the carbe til is does, this will give you a smoother throttle response.

Melvin

john e. holliday · « **Reply #9 on:** July 26, 2010, 10:51:23 AM »

Quote from: Bob Heywood on July 24, 2010, 09:33:38 PM

I would move cautiously on this one. The line tension will only equalize at one discrete point over the total range of travel.

I have a brand new Roberts Upright unit that is yours, on the house. PM me your address.

Bob Heywood
Dayton, OH

At the high speed the tension should be the same for all three lines.

Author Topic: J-Roberts Handle with Brodak Belcrank (Read 795 times)

Bob Reeves

J-Roberts Handle with Brodak Belcrank

Paul Smith

Re: J-Roberts Handle with Brodak Belcrank

john e. holliday

Re: J-Roberts Handle with Brodak Belcrank

Bob Reeves

Re: J-Roberts Handle with Brodak Belcrank

john e. holliday

Re: J-Roberts Handle with Brodak Belcrank

don Burke

Re: J-Roberts Handle with Brodak Belcrank

Bob Heywood

Re: J-Roberts Handle with Brodak Belcrank

Bob Reeves

Re: J-Roberts Handle with Brodak Belcrank

Melvin Schuette

Re: J-Roberts Handle with Brodak Belcrank

john e. holliday

Re: J-Roberts Handle with Brodak Belcrank