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-   -   Top Flite B-25 ARF (Tecnical, tips, suggestions) (https://www.rcuniverse.com/forum/arf-rtf-75/6494380-top-flite-b-25-arf-tecnical-tips-suggestions.html)

ronbell 03-02-2011 07:03 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Dave, it's hard for me to be sure how the aircraft would repond in HH mode if you made a rudder stick input. When HH mode is selected the rudder stick becomes a YAW RATE control instead of a rudder deflection control. Effectively the stick is now telling the gyro how many degrees per second that you want to aircraft to turn at and as a result the gyro will deflect the rudders as much as it needs to in an attempt to achieve that turn rate. I really would expect this to result in the rudders being slammed hard over for relatively small stick inputs - not a good thing!! Personally, I don't intend to try it. I will only be using rate mode.

Ron.

djstar39 03-02-2011 07:43 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Ron, last season I inadvertently left my gyro switch in HH mode while taxing down the runway. I was using the rudder stick to turn as you normally would and it was all over the runway with hard turns either way. Took me a second to figure it out that I was in HH mode. Back to the need for following a checklist. Simply too many switches to make sure they're in the right place (both battery switches on, gyro, flaps to 10%, BB power switch on, BB release switch set, brakes off (and then on), top turret spinning, etc.)

I do know folks use gyro's in HH mode for takeoff on jets and other aircraft and I'm thinking that they line up on the runway, waggle the rudder back and forth 3 times to set the new neutral and then takeoff without bumping the rudder and then switch off the gyro, gear up, flaps up, etc.

ronbell 03-02-2011 07:54 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Dave - I think you are correct. Much too risky for me.

BTW, with the 401 gyro in HH mode waggling the stick back and forth quickly 3 times then releasing it tells the gyro to return to the neutral position that it established at power up. It does not change where the neutral position actually is. The only way to do that is to power the gyro down and back up again - the gyro looks at the input signal during power up and remembers that as 'neutral'.

RCGuy41 03-02-2011 08:04 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
djstar39,

After reading your last two posts you are right, after start up the pilot will need to turn the gyro off to prevent the gyro returning the plane to its original heading. Yes before initial TX and RX battery on always ensure your switches are in the correct position. You are also correct about the gyro in HH mode during take off, to add on some more info, as the engines reach max RPM torque pulls the plane to the left, the gyro senses the turn and compensates for the torque generated by the engines hence the bird stays strait down the runway until it reaches flight speed, small touches on the rudder stick won't change unless the pilot tries to over correct the bird while in HH mode. We need to remember these gyro where originaly designed for heli use, ronbell has provided excellent back ground information so we can set up said gyros and have them work in our Bombers. I believe Normand was the first to incorperate a gyro into his bird and I learned from him. I have been flying my B-25 for three seasons, this being the third and I have enjoyed every single flight and have never had an in-flight emergency. Speedracer on the ofter hand has had a few of his own and has saved his aircraft. All in all we need to do our own research and apply what works for us and provide positive feed back to the rest, hopefully all this info will help another who has run into the same problems. Just my two cents gents sorry for the rambling.

gregory.aldrich1 03-02-2011 09:06 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Okay, all very very helpful. My take on it is this, I have a choice then whether or not to use heading hold for take offs and landings. My first impression for using HH in take off and landings is, No. It will be my dumb luck I will forget to switch the damn thing off in all the tension and I'll have a dumb look on my face while I am scooping up the remains into a hefty bag. No, I think I will stick to the regular rate settings to help control waggle on roll out and the old tried and true method of controling the rudder. That's what I've been doing with tail draggers since I started flying them. I think I will turn my rudder rate down low on low rates to compensate for oversteer. I think I will also be utilizing the flight mode switch as to combine my settings into one single switch. That way, in position "0" on flap switch (FM switch) rates will be set for takeoff. the gyro rate will still be set using the "Aux2" channel and switch. Position "1" will be for flight and position "2" will be set for landing, incorporating my landing flap settings, elevator compensation setting and auto land feature where the flaps will retract automatically upon 3/4 throttle as in an aborted landing senario. I think I will set up my gyro to work like this: Position "0" on three position Aux#2 switch will be for power up, gyro set to 80% on gyro sys screen. Next position "1" will be set in rate mode at 10% for take offs and landings. This will increase the gyro rate to compensate for ground waggle and final approach gusts. Finally, position "2" will be set at a modest rate of 25% for a less sensitive flight. I did check my reverse setting on the gyro and found that it was correcting in the wrong direction. In essense, was going to make the problem worse. It was a definite crash senario waiting to happen. Thanks a bunch for that pointer.
My final question on the subject, and let me tell you, I am eternally grateful for the response and it has been most helpful. My question is this, if I set my take off mode to reduce the rudder sensitivity from my TX, in other words, very low rates with plenty of expo, will the Gyro still compensate (do it's job) with input deflection all the way up to it's max setting? So my normal inclination without a gyro, say on a tail dragger warbird, is to really soften up the rudder with expo and reduced rates. That's how I have accomplished pretty straight roll outs into a clean straight take off. If I still do this, does the gyro still have it's own "max" throw which it will input to correct anysudden yaw?
Again, thanks for the help guys. Oh, and for those who do not have actual names for handles, could you sign your posts or have a signature placed by default? I'm having a hard time remembering everyone's name.
Greg

djstar39 03-02-2011 09:28 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Greg,

Figuring out this stuff is fun isn't it? When you finally master it, you'll really feel like you've learned something!

I had my rev switch wrong also. I would switch on the gyro on the bench, move the tail and watch the rudders move. Looked good to me. My buddy pointed out that they were going the wrong direction. Would have DEFINITELY made the problem worse. Felt like an idiot. Really don't mind feeling like an idiot with my plane safely on the bench. In the air...? No thanks!!! ;)

Regarding the auto land feature. I initially had this set as well on this bird and another GS P-51 and someone convinced me that this might not be the best thing. The situation they described went like this: You're low and slow on final hovering near stall speed and get into trouble (someone's in the way, wind gust, not lined up, whatever). You decide to go around and throw in the throttles... most would go to full power depending on how icky the situation was. With the autoland, those flaps are coming up reducing lift. Now you're low and slow and haven't built up some good airspeed and you remove the additional lift from the flaps. Might auger in.

They convinced me that I could throttle up on my own, build up airspeed and then remove the flaps manually when it felt ok. Not trying to convince you at all... just something to ponder.

I don't know the answer to your question as to how the gyro controls the rudders with expo and rates involved. I might have to test it on the bench to see.

Dave

ronbell 03-02-2011 09:47 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Greg - the answer to your gyro question is YES, the gyro will still 'do its thing' regardless of your expo setting.

Ron.

RCGuy41 03-02-2011 10:28 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Greg,

in the video the gyro is doing what it is suppose to do just think about it on the B-25 with an eng out. http://www.youtube.com/watch?v=wc2-fL81YJU

This video might help but it's for heli's, I believe it might help answer some of your questions. http://www.youtube.com/watch?v=y6cRRhGzx-w

gregory.aldrich1 03-02-2011 10:58 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Hey Dave, I don't recall what radio your using, but the 9303 has a function to slow down the flaps up to 2 seconds from point to point. If this feature were part of the setup, not only would it be more scale like, but in that event where a sudden "go around" were to take place, the slow retraction of the flaps would suffice, no? Just curious. I am trying to remove some of the steps for flying this bird and if I have most of everything on one single switch, it makes it allot less likely that I will forget to do it and suffer the events that might happen because I forgot to. What do you think? Two seconds of travel time from fully deployed to retracted. Think it would be enough?
Greg

djstar39 03-02-2011 11:21 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Greg, I'm using the 9503 for the Bomber and a 9303 for the bomb bay, bomb release, landing lights, top turret. I do have the flaps on the 2 second delay and this would definitely help with the autoland feature.

Are you going to deploy half flaps on downwind and then full on final? Each step would take two seconds. Going from full down to full up would also be 2 seconds. I can't remember how the autoland works... So you have full flaps and go around, throttles go past 75% and flaps come up. But does that also mean that if you decrease throttles below 75% that the flaps go back down? Can't remember...

Dave

gregory.aldrich1 03-02-2011 03:08 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Don't quote me on this, but I am pretty sure that after you decrease the throttle again, the flaps deploy as they were when the landing was aborted. But by then, I imagine I would have switched back to another mode to go around. Never had an aborted landing that required the use of the autoland feature, but that is a good question. Give me a couple days and I should have the wings hooked up and I will tell you after I find out.
Just had our monthly club meeting tonight and got the rest of the parts that my friend and I were painting. Redid the nose gunner deck in a royal air force interior green. Painted inside the nacelles to add scale. By the way, I picked up two 1/9 scale pilots from Hanger 9 that with a little shoulder trimming, fit side by side in the cockpit, so I didn't have to use the 2D crew they (TF) supplied. I mean really? for the price you would think a set of rubber wheels and a couple decent 3D pilots would have been a given. I mean, look at their other kits for way less that have them. Anyway, not a big thing, but honestly, I think they wasted good wood on pilots I think most guys would prefer not to use. Now, I may use the tail gunner supplied only because it is cramped and it's easy. But the pilots? Naw, so anyway, after that very minor scaling out of the cabin, it looks better. Now I just have to make a bulkhead wall behind the pilots to glue the picture on that appears to go back in the plane. Not that you would see it through the tinted windows, LOL. Anyway, will resume some building over the weekend and then it's back to the grind next week. Looking to have it ready to maiden this month! Sure has taken long enough.
Oh, here is a question for those who broke new engines in on their birds. Did you install the dummy cowls right up front or did you wait until the engines were well broke in first? Just curious. Normally I wait until I am sure the engine has settled and adjustments become very infrequent. That's how I guage a four stroke has "settled". But this one is different. Not having those 14's there in place seems almost a crime. Might as well fly it without a cowl for that matter. Anyway, too much to drink and I think I am praddling. Nite.

gregory.aldrich1 03-02-2011 10:27 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
1 Attachment(s)
By the way, here is a pic of the "mess"..

ronbell 03-03-2011 09:51 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
1 Attachment(s)
Looking good Greg - that's not messy at all. I like your idea of using a picture of the real insides for the back of the cockpit. I took a different approach and decided to make the cockpit canopy removeable (using heli canopy screws) and moved all the switches, etc. to the back panel, picture below.

I see that you are using a much larger servo arm for nose steeering that I was planning on. Since you will be flying long before me, and you are using the same gyro/matchbox set-up, I will be really interested to get your take on nose steering sensitivity and the like. You've probably figured by now that I'm a little nervous about that, mainly because my take-offs aren't always as straight as they should be!!

I'd also welcome any advice and pointers regarding the air retracts. This will be my first time using them and I keep hearing horror stories but don't know whether they stem from poor set-up, inadequate maintenance,or what.

Ron.

RCGuy41 03-03-2011 11:46 AM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Ron,

What questions do you have on retracts? I have retracts in four of my birds and have had them in a spitfire that I no longer have. I have Robarts recommended landing gear in my bomber, so please ask away?

ronbell 03-03-2011 12:17 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Thanks Bradley, the truth is that I am currently at the point of not knowing what I don't know!! They seem straightforward enough but I frequently hear comments like "shame you can't convert them to electric", "saw another guy belly land a beautiful plane at the weekend when the gear wouldn't come down", "even when they come down they don't always lock reliably", and other such confidence destroying things. I'm really looking from some guidance from people like you who have used them successfully to tell me the most important do's and dont's. For example, is there anything that I ought to disassemble and check or lubricate? Are there any tricks that help minimize the chance of leaks? Since I am planning (if it fits in the car OK) to keep the inner wings in place during transport so should I leave off the quick disconnects? - I plan to install them to make maintenance easier in the event that I do need to remove the wing.

I tend to be very risk averse so, when faced with something new, I look for everything that could go wrong ... as my lottery ticket purchases attest, my luck is not the best!!

Ron.

djstar39 03-03-2011 01:24 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Ron,

I'm using Robarts with brakes. I run Robarts on a lot of my planes... not sure if that makes me an expert but I do have opinions. :D I would use the quick connects at the fuse to the inner wing. When you need to take them off for maintenance, you will be glad you did. On all air connections, I either use the nuts that you screw down over the tubing to the connection or I use some very thin wire to (like on the quick connects) to go around the tube in through the holes in the white connects and I just twist tie them to make absolutely sure they don't come off.

Once you have the whole system plumbed, do the soapy water test on every connection. You can also air up the system and come back a couple hours later and check the pressure. For my brakes, it keeps the air in the tank for weeks (I must have done a good job there).

On the air valve, make sure the round nut that holds the valve to the wooden mount is tight. I've had them come loose and then the servo just moves the entire valve back and forth (translation, gear doesn't go up or down).

Many times retracts don't do what they're supposed to do because they get bent when either landing or taking off. I always cycle my gear before every flight to make sure nothing's sticking. If you're on a grass runway, you'll still run the risk of bending something on takeoff which might impact the gear coming back down. Because the gear on the B-25 go straight back, there's less chance of this happening. On fighters where the gear close parallel to the wing, you'll see this problem more.

The front gear pin is soft (on purpose). They want it to break away if too much stress is put on it. Buy some extra. I've had one break.

The gear doors introduce a completely different aspect to this. Take a lot of time to make sure these are good and there's no binding anywhere. Check it before each flight.

Setting the tension on the valve is another area where you can play. Some folks remove them and let the gear slam up and down (I can admit to this). Some set them so the gear go up and down in a scale manner. Set them to your taste but make sure they're tight or they'll work loose and you'll find them somewhere in the fuse.

By all means... DO NOT hit the retract switch while you're on the ground. And make sure it's in the right position before you turn on the transmitter and receiver. At some point you'll forget or do an oops and then you'll have gear doors to re-attach. Nothing sucks more than doing this!!! Back to that checklist thing again. I've always thought there should be a way to program a mix or something so that this could somehow be avoided. You can also put it in it's styrofoam cradle until you're ready to fly. Most probably wouldn't do this.

Hope this was helpful! BTW, as long as your engines spool up together, I've found this B-25 to run straight down the runway. Not anything like a tail dragger where you need lots of right rudder.

ronbell 03-03-2011 01:28 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Very helpful Dave - thanks!!

Ron.

gregory.aldrich1 03-03-2011 04:04 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Hey Ron, anothr point of interest when it comes to the gear. Dave was spot on in all that he said when it comed to retracts, at least air retracts. For the money, robart is a good choice. I wanted to weigh in and just give this bit of info. I decided to go with the McDaniels glow drivers for the saito's and in turn had to disassemble the nacelles and while I was doing that, I thought it would be a good idea to paint the insides and take care of that little scale detail. Well funny enough, I picked up the fiberglass nacelle and wanted to check out how the gear doors looked all painted up. Mind you, I spent hours with a boiling pot of water to remold the gear doors into the proper shape of the nacelle. So they fit pretty tight. Unfortunately a little too tight. A couple times while cycling the gear after the first time I installed and after I added the metal levers, I noticed they were sticking and not opening. I didn't give it much though because I figures I would deal with it once I got the whole system up. I was only using a can of spray air to actuate the gear. Anyway, I had a hard time pulling the gear doors open. Three of the four, hot being hooked up to the the lever system were sticking. I actually had a hard time opening them. Remember this, air retracts are weakest at the closed position and it doesn't take allot of force to keep them shut. The fiberglass gear doors are binding because I have them too straight. I can see I am going to have to lightly sand off the part of the edge where the two finishes come together, essentially the seem kine between the gear doors and the nacelle. I've identified a spot each on two and two spots on one door where they bind. I think inadvertantly I found my closed door, not wanting to deploy binding problem. Just a word to the wise. If you have binding when trying to lower the gear from retract position, check those edges of the doors and see how they open when they are disconnected from the lever mechanism. By isolating the doors to themselves, without any interference from anything else, you can determine whether or not they are binding in any way. It was my only problem I had not gotten into yet and like I said, I think that problem was identified by accident. That's all. Hope that helps.
Greg
ps. Only by habit did I hook up a large horn on the steering. When I see cables, I just automatically start thinking oversizr horn. I definitely have a small turn radius! I also fly off of grass and turn my rudder output way down with allot of expo to control torque drift on roll out. But, I may have issues anyway and if I do, I will certainly post something about it. Have a good night ya'll.
Greg

Speedracer2112 03-03-2011 05:04 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Hi guys!

WOW! Gyros 101 +. I still will try it some day. Ive been lost in my B-17 for quite some time and appologise to my B-25 often. I maidened the B-17 last week so my TF B-25 will start seeing the field a little more.

Her maiden can be found here. Totally off topic so dont look if you dont want to see it.

[link=http://www.youtube.com/watch?v=GgyotNO3XrA]B-17 Maiden[/link] She has a QuadSync installed that I turn on and off for take off and landing.

I also picked up a video camera so my B-25 is in the que for some film soon.

BTW,
I tried to read all of the new posts but its difficult to read some of them as they arent broken up (huge paragraphs) and difficult to read. Try to remember to do this. It really helps the okd guys like me read them.

Cheers!

SR

picard1 03-03-2011 05:42 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Ron,
When you can, could you post some picks of your canopy mod and how the Heli screws work...


Mike

djstar39 03-03-2011 06:29 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
SR,

Wow! That B-17 maiden was awesome!!! Is there another thread out here you've been posting to for it? Don't want to detract from the B-25 thread.

Awesome!!

Dave

RCGuy41 03-03-2011 07:28 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Good evening Ron,

Dave has said it and I concure with his asesment and setup; I have done the same. I do agree with adding .020 safety wire on every airline going into a T-fitting and or gear and finaly your choice of valve. I would recommend you stay with Robarts air control system, use the air-control valve with the metering valves which control how fast the gear raises and comes down. As for the gear its self, depending on how many flights are put on the bird and the number of cycles one would need to change o-rings once every other season. During the off season try to get a small amount oil into the cylinder to keep the o-rings from drying out and rooting.

As for the TF B-25 you will find out when installing the mains, the directions tell ya to mount them all the way to the rear of the mount bracket. Okay that's all well and good but, when you install the cam for the gear door you will find out as the gear comes down and engauges the cam the cam hits the end of the retract. The simple fix to the problem, there is a brass schim the cam connects to just turn that around 180 and use a 1/8" longer wood screw. Before you install the light ply cam lever I would try to find some basswood and remake the levers or soak them in some CA to harden them. Check out this guy's website, he built a TF B-25 and sequenced the doors at http://www.rcdon.com/html/top_flite_...ell_proje.html it's pretty detailed but an excellent resource if you get into trouble and want to see how some one did something. Good luck I believe you are on the right track and as always if you have any questions all you have to do is ask.

RCGuy41 03-03-2011 07:31 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
SR,

Awesome video of your maiden, congrats.

RCGuy41 03-03-2011 07:39 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Ron,

One way to attach your gear doors use small 4-40 counter sunk screws with small bolts on the inside. I have found out the hard way that epoxy works for a short period of time before they brake or the bracket seperates from the glue. As Greg and Dave have mentioned do your checks before turning on power; I forgot to turn my gear switch up, I turned on the TX and then the plane, my receiver did it's check then I saw the bird sit down on gear doors and the ADF antena went through the bottom of my fuse. The fuse was easy to repair to include regluing the gear door bracket back onto the nacelle.

ronbell 03-03-2011 07:54 PM

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 
Mike, I haven't actually done the canopy mod yet, just have in my head what I am going to do and have bought the parts. Here is a link to the screws I will be using (after I paint them OD)...

http://www.ronlund.com/mm5/merchant....ry_Code=BRAFMP

They fit a 3mm blind nut. I expect that I will have to build up the cockpit side rails a little in the area where the blind nuts will go. That should be easy enough and not visible from the outside. I wish there was a scaled down version of the dzus fasteners that are used on real aircraft - the ones that lock/unlock by a 1/4 turn, but I haven't found anything like that yet.

Greg - many thanks for the heads up about the gear doors. I will definitely be watching out for that. I have already painted the wood nacelle structure gray but have not got to painting any of the fiberglass parts yet.

SR - Awesome job on the B-17 and congrats on such a great maiden flight. I have an original pilot handbook for the B-17 autopilot as my dad worked on those and B-24's in WWII. You can't help but love that aircraft!! Also - you're either not that old or you're holding up really well http://www.rcuniverse.com/forum/js/f.../msn/49_49.gif

Ron.


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