Author Topic: J Roberts 3 Line Handle - Push or Pull ? (Read 2489 times)

Paul Stein · « **on:** May 24, 2009, 03:16:27 AM »

Guys.....

Undertaking a little survey or 'analysis' on the preferred method of throttle activation using the J Roberts 3 Line handles.

In Australia the accepted standard (even 30 years ago) has been to push the trigger forward for full throttle...and pull the trigger back for engine idle... one theory in this configuration is that if the model loses line tension (control wires) the engine speeds up.. I think...

Any advantages in having the throttle on the handle operate in any particular direction?

So do you push or pull?

Paul

Wayne J. Buran · « **Reply #1 on:** May 24, 2009, 03:37:30 AM »

I push forward for low speed. Always have. I hadn't done carrier for twenty years so three yeras ago when I came back I was corrected to do push forward for low speed. I'll check with Gary and Dan this morning as we are getting together to fly in a few hours.
Wayne

david smith · « **Reply #2 on:** May 24, 2009, 07:59:46 AM »

I pull for high and push for low. I think my "theory" for doing that is when you go fast it feels better to just squeeze and hang on to everything, then to start to loosen, slow down, and relax for low speed. Something I would compare the push high and pull low to would be real airplanes because most are push the throttle forward for full and pull back for low.

David

Mike Anderson · « **Reply #3 on:** May 24, 2009, 08:35:02 AM »

Quote from: Paul Stein on May 24, 2009, 03:16:27 AM

Guys.....

Undertaking a little survey or 'analysis' on the preferred method of throttle activation using the J Roberts 3 Line handles.

In Australia the accepted standard (even 30 years ago) has been to push the trigger forward for full throttle...and pull the trigger back for engine idle... one theory in this configuration is that if the model loses line tension (control wires) the engine speeds up.. I think...

Any advantages in having the throttle on the handle operate in any particular direction?

So do you push or pull?

Paul

I pull for high/push for low (actually have my springs on my handles which pull them to low throttle). I have seen references in the past that most scale flyers use a push for high speed, while most carrier flyers use a push for low speed. Don't know how accurate that is, though all the carrier guys I know do it the same as I do.

As for the "slack lines" tending to go to high speed, that would depend on your bellcrank and throttle arm arrangement. I doubt if it also would apply to correctly matched handles and commercial bellcranks as the THEORY would be that the doubled drag of the two elevation lines would tend to pull the throttle to high speed (this also implies that it is set up for a pull-to-HIGH). That theory ignores the fact that the two elevator lines are pulling on a moment arm that is half as long as the throttle bellcrank's. That is the reason for the J-Roberts and LR/Brodak bellcranks using a 2:1 ratio in the throttle cranks motion -- so that the two elevator line's drag is balanced by the one throttle line's drag. Otherwise, you would ALWAYS have to fight that drag differential to change a throttle position, no matter what the speed.

(Dang .. now I've used up all my mechanical engineering brain cells for this week)

Balsa Butcher · « **Reply #4 on:** May 24, 2009, 04:48:11 PM »

Just a thought: In full scale airplanes pushing the throttle increases power - sort of like going forward with the throttle trigger. Maybe that's why scale guys like to set things up that way? No logic, but this hobby isn't always logical. Pulling back for throttle seems more intuitive to me - sort of like a motorcycle throttle.

Mike Anderson · « **Reply #5 on:** May 24, 2009, 05:38:29 PM »

Yeah - I think with me it was that it felt more like a slot car controller, which wasn't ALL that distant in my past at that time. Squeeze the trigger to make it go ... Also, back then, the SuperTigre throttle arm was push for low and the J Roberts bellcrank that I used supplied a push for low when the throttle trigger was released and a pull for high when the throttle trigger was squeezed .. just the way it worked out, I guess.

I did end up with a hand-me-down plane one time that worked backwards from what I was used to and it wasn't all that hard to switch back and forth, but it never did feel quite right.

bfrog · « **Reply #6 on:** May 24, 2009, 10:14:23 PM »

I started carrier flying after I had done some RC car racing so pull for high was a natural thing. It just seems right to me others may have a different idea.

As far as loosing line tension what I have found is that if you look at the Brodak (or Roberts) handle when you have it set up for pull for high, the throttle line goes slack when you pull the trigger. So that means to me that slack lines tend to make the throttle go high. I have had one or two bad moments because of this. On one occasion I was trying to set the throttle linkage and was doing touch and goes on asphalt. I landed, taxied for about 1/3 of a circle and somehow a stone or something on the ground caught the lines. The plane went to full throttle, turned in at me and flew over my head. When the lines went tight again about 180 degrees later the safety thong tightened on my wrist and pulled. A 45 oz plane going probably 70 to 80 mph has a lot of pull to it. It raised a huge welt on my hand where the thong tried to pull my wrist off, took a week or more to go away. Painful and very scary.

Paul Stein · « **Reply #7 on:** May 24, 2009, 11:47:31 PM »

Quote from: Mike Anderson on May 24, 2009, 05:38:29 PM

Yeah - I think with me it was that it felt more like a slot car controller, which wasn't ALL that distant in my past at that time. Squeeze the trigger to make it go ... Also, back then, the SuperTigre throttle arm was push for low and the J Roberts bellcrank that I used supplied a push for low when the throttle trigger was released and a pull for high when the throttle trigger was squeezed .. just the way it worked out, I guess.

I did end up with a hand-me-down plane one time that worked backwards from what I was used to and it wasn't all that hard to switch back and forth, but it never did feel quite right.

Looking at the original J-Roberts install doco it would seem that it is indeed 'pull' for high and 'push' for low throttle...

mmmm.... maybe because we Aussies are on the bottom of the world things are the other way around ;o)

Paul

Wayne J. Buran · « **Reply #8 on:** May 25, 2009, 04:11:55 AM »

The concensus at flying sunday morning was that you grab and hold on at high speed. Push forward to slow. It seems more difficult to keep forward at high speed if that makes sense.
Wayne

don Burke · « **Reply #9 on:** May 25, 2009, 10:52:34 AM »

"... the Brodak (or Roberts) handle when you have it set up for pull for high, the throttle line goes slack when you pull the trigger...

Slack lines are a safety problem. The entire weight of the airplane is on one line. To me there is need of adjustment of leadout or line length to get no slack over full throttle travel. This sometimes happens when mixing and "old J Roberts handle" and a new "Brodak bellcrank" or vice versa. Seems like the slot in the bellcrank for throttle travel is different length on the two versions.

eric conley · « **Reply #10 on:** May 25, 2009, 06:49:31 PM »

When I started flying carrier back in the early 90s I was asking a lot of questions of Bill Bischoff who at the time was doing quite well in carrier and also contributing a lot of "how to" articles to the HiLo news letter. One of those questions was do I push to go fast or pull to go fast and his ansewer was that he pushed, so thats what I did and still do. It has certainly worked well for me although I must say that the vast majority pull to go fast and this can make it rough when you want to let someone fly your plane and you find out that they pull instead of pushing to go fast. For me thats a deal breaker.
I have found that I can't do it either way, especially if I get in a tight spot and need some instant input. So when I hear someone say "Oh I can go either way, doesn't make any difference to me" I think to my self "makes a big difference to me" so I pass on letting them fly one of my planes. I had never thought about what Don mentioned about the pull shifting on the lines and will have to think on that as we need the pull to be the same on all the wires. This could be be where the saying comes from that when you pull test you do it with the trigger pulled back. I heard that one a lot when I first started carrier.
I'm left handed so when I'm flying the HS portion of the flight my left hand holds the handle and my throttle finger is pushing forward on the throttle trigger and my right hand fingers are rapped around the front of the handle with my thumb pulling foreward on the potion of the trigger Assembly that stick out the top of the handle. All this helps me get the handle as close to my stomach area as possible during the HS portion of the flight.
To me the bottom line is that do it the way that works best for you and usually thats probably the way you started with when first learning how to fly carrier. I think we all should take note of what Don said about changing the line load so they are not the same for each line when you pull for speed?? eric

Peter Mazur · « **Reply #11 on:** May 26, 2009, 11:17:36 AM »

I'm one who always pulls for high. It makes a difference to me, and I would not try to fly anything set up the other way. Like Eric, once the direction is ingrained in the body, it is hard to do otherwise.
On the loose-line concern: If you are set up to pull for high throttle, then if the line lengths are not exactly right for high speed, you have slack in the center line. If you push for high throttle under the same circumstances, ou get the two elevation lines with slack. That's worse. However, it usually works out. If you don't have a death grip on the trigger, the high tension will cause the line tension to more-or-less equalize, so there will be no slack lines. The unequal line tension can only be overcome by a really strong trigger finger. So relax your finger a bit and the trigger will move until the line forces are distributed evenly but still allow you to be at full throttle. You only need the same amount of trigger force at high as you have at low in order to control the throttle, and any more force than that may just go to making the line forces unequal.
For pull tests, the same sort of rule applies. Don't pull or push and the line tension will equalize, spreading the load and minimizing the load in any one line.
Did anyone notice on the J Roberts instruction sheet: 0.012" diameter stranded lines are strong enough for any model with an engine up to a .60. Yeah, right. Do you want to stand next to my Class 2 at speed with .012's?
Pete

Wayne J. Buran · « **Reply #12 on:** May 26, 2009, 01:03:51 PM »

A recent issue with my profile hunting was eventually exposed when I found that the throttle line had tension in high speed. I use the trigger pulled back for high speed. I substituded a line clip that was 3/16 longer and away went the hunting. I must assume that the throttle line needs a slight amount of slack so as not to be loaded versus the the elevator lines. I have set up a lot of lines in my life time and have found there is no way to make line length exact. That said, you would need the leadouts, handle leadouts and line lengths matched exactly for the load to be equal on all three lines. I am very sure that it's not really possible. Relative to the original question, I find pull on high speed more comfortable and safe. See youa at Brodaks.
Wayne

dale gleason · « **Reply #13 on:** May 30, 2009, 08:38:15 AM »

I pull for high speed. Billy B. pushes for high speed. He can go either way which is good to help others out. But he was helping Dave Ek get his A7 working, and Dave said he goes the "other" way, No problem for Bill. Except Dave meant he gives "down" to go "up".
It's all communications.....dg

john e. holliday · « **Reply #14 on:** May 30, 2009, 09:06:17 PM »

To all, there are tools out there that you can get to make line clips. Mine came from Carl Shoupe. Using the hard point handles in stunt makes for fun tryjng to get equal line length. With the various line clips of different lengths solves all that problem. When and if I get my carrier done I will do some pull tests on the clips I have made with the tool. DOC Holliday

roger · « **Reply #15 on:** July 03, 2009, 11:47:28 AM »

ya know i just got done reading the article on push or pull, is there anywhere that tell about getting your lines right? im having a problem with that, its either two long or two short line clips help but but how many to use is the question. how do you measure them?

skyshark58 · « **Reply #16 on:** July 03, 2009, 07:44:03 PM »

One line clip at each end of each line is all you are allowed to use per AMA rules. No double clipping allowed. Mike

Mike Anderson · « **Reply #17 on:** July 03, 2009, 09:15:51 PM »

Quote from: roger on July 03, 2009, 11:47:28 AM

ya know i just got done reading the article on push or pull, is there anywhere that tell about getting your lines right? im having a problem with that, its either two long or two short line clips help but but how many to use is the question. how do you measure them?

I try very hard to finish the lead-out ends so that they match the handle leadouts ('mirror image', actually). Then I try very hard to tie all three lines exactly the same length. Then I always roll the lines toward the plane and leave the plane end connected - each model gets it's own lines, and the handle(s) all use the same equal-length clips. Also, each model is marked with a Sharpie at the wing tip which handle is the correct one for that model. There MAY be some small differences in the handle leadouts, especially, once I've re-done the handle leadouts. Don't mix up and connect a J-Roberts handle to a plane that was matched to an LR/Brodak handle - the throws are different.

Wayne J. Buran · « **Reply #18 on:** July 04, 2009, 04:03:01 AM »

Mike is correct, keep everything segregated by airplane. I do the same and it is somewhat difficult to get the leadout lengths correct but its worth the effort. Smooth controls payoff.
Wayne

john e. holliday · « **Reply #19 on:** July 04, 2009, 11:02:17 AM »

I remember Ray Wilman setting up his carriers in the early days. He did not use clips. He used a music wire to connect handle to the lines. They were permanently attached as in those days we only had one class of carrier. I have been flying Roberts style bellcranks with the new handles with no problem. Just make sure when pull testing that tension is on all three lines. DOC Holliday.

Author Topic: J Roberts 3 Line Handle - Push or Pull ? (Read 2489 times)

david smith