ARC PUSHROD QUESTION

HI ALL,
The ARC comes with 3 holes in the bellcrank for the pushrod to the flaps. Mine has the pushrod in the hole closest to the pivot which is about 7/16th from pivot is this correct?...Thanks

>HI ALL,
>The ARC comes with 3 holes in the bellcrank for the pushrod
>to the flaps. Mine has the pushrod in the hole closest to
>the pivot which is about 7/16th from pivot is this
>correct?...Thanks

Greg,

Ya know, we sometimes are treated to a visit from the guy who claims to have done such a sterling and complete job of massaging these ARFs and ARCs for Brodak prior to giving approval for production.

That's funny, we don't seem to see him around when a series of questions like yours are brought up.

Your setup sounds a little slow, but then I don't know the dimensions of flap horn.

If I don't know what is needed on a new model, and the plans are not clear or appear confused, I will mock-up the controls. Sometimes I will even temporarily attach a CL handle to the leadouts just prior to nailing the control system in. Looks a little stupid "flying" the model from near wing tip, but it also gives ratios which are generally pretty close.

In any case, it is good to refer to a similar model you own and which has control ratios you like, replicating them in a new model.

If really worried about it, I think the hatches used on Top Flite's ARF Flite Streaks to be a pretty good idea.

Hi, Greg - Sterling here! I use this site from work (limited access) so I can only scan it now and then. In any case, we tried the pushrod in the two inner holes and the position closest to the bellcrank pivot seemed to work best. As alluded to, control response seems to be a personal thing and is influenced by a number of other factors involved - You can leave the pushrod in the inner hole and still dial in your preference via horn hole position. We did find that a 1-to-1 ratio worked best. I'll try and check on the exact horn positions tonight - can't remember wear I set them.
Seven engines were tried - my favorite was the SAITO .40 with the LA .46 in close. By the way, I had to add around 2 ounces of tailweight with the heavier engines. Try adding in 1/2 ounce increments untill you feel it's right for you.
And, note that the prototype has a bit of play between flaps and elevator - it's just been like that since day one. It may not help but it does not seem to hurt.
After around 150 flights, I have found absolutely no sign of wear at the bellcrank/leadout interface.
Hope this helps.
Bob Z.
PS - has anyone built and flown the ARC Cardinal yet?

the slop in the flap/elevator linkage is so that the flaps operate before the elevator does, thereby reducing pitching with small control inputs. less pitching equals better scores! i remember reading that in model builder waaaaay back in the early eighties and tried that (along with thick stabs and thin elevators) when i spun around and around in my previous life....the one before xmtr crystals, third order intermodulation, frequency flag fights, etc. etc. jeez, i love u-control!

LAST EDITED ON Oct-19-04 AT 05:35 PM (CDT)
 
Tom Morris wrote an article in Jan/Feb 2004 issue of Stunt News, pg. 42, that adresses bellcrank and control horn ratios. I believe this article will answer all your questions. This information may also be available on Tom's web site, but I have not checked.

Regards,
Phil

LAST EDITED ON Oct-19-04 AT 05:38 PM (CDT)
 
I have not finished mine yet, but it's gone from an "ARC" to an "RC" over the course of a bad weekend for flying.

I left the flap pushrod in the inner hole (after cutting open the sheeting to take a look see at everything). My flap pushrod goes to the outer hole in the flap horn and the elevator pushrod goes from the middle hole to the middle hole on the elevator. I'm seeing 1 to 1 control with a total of 30 - 40 degrees.

I suspect that will be okay, but if that's not enough, I'll move everything in one hole and try again. Real scientific.

I use and recommend the TLAR System when possible.

EDIT: Also, to ease your fears from another thread: I know the crimped, unbushed leadouts are not as elegant as I would have done had I built them from scratch. But I have seen other unbushed leadouts work on nylon bellcranks for years with no problems. You will probably wear out the piston and liner before you wear through the bellcrank.

Enjoy,

Ron King

To add a bit more data - I went home and checked the prototype for some numbers.
Regarding push rod locations:
Inner hole on bellcrank to middle hole of flap horn.
Upper hole on flap horn to upper hole of elevator horn.
Other factors
Balance right at aft edge of L/E planking
About one-half ounce tip weight
Around one degree engine offset and a bit more on the rudder.

I repeatedly brought the prototype to the field and left it out for anyone and everyone to fly - it was flown by everyone from beginners to top level experts. There were days when it flew continuously for three or four hours. Most of the flights were with the LA .46, on 63 foot lines, Hot-Rock handle. We also flew it with an ENYA .45, a Brodak .40, an OS .40 4S, and a Magnum .40.
I did the same at the Brodak Fly-in - offered it to anyone wanting to enter it and many took me up on it - It did quite well.
The most prevalent suggestion was to add more tail weight.
Hope this helps.
Bob Z.
ps - how about some others sharing experiences and suggestions.

LAST EDITED ON Oct-21-04 AT 05:25 PM (CDT)
 
Hi Greg

On the Oriental ARC the Z-bend should into the middle hole in the bellcrank to the top hole of the flap horn. The Elevator push rod should from the middle hole on the flap horn to the middle hole on the elevator horn. I bushed my control horns to remove the lost motion.