I have spent the last week building my first RC model. A LMH Corona. I want to thank you guys who answered some simple but critical questions from a new guy. I'm down to the last tedious details, which seem to never end, and I've run into, what seems like a major problem. Individually, the main rotor assembly and the swash plate assembly moved freely and I'm thinking, GREAT, all I have to do is mount the rotor head on the shaft, finish up and let's go flying. Well I mount the thing and now it's stiff as heck. Everything seems level and I've followed the very well done manual, but I can't figure out why the thing is so darn stiff. I would really appreciate some advice...

Thanks,

CB

the bering blocks dont always align rite so just run ti slow and tighten the bering block in while it's runing so that the breing blocks get alligned. Also, make sure your main shaft is not bent as this will cause it 2 bind amazingly. Hope that helps!

I am a bit confused. At what point does it turn smoothly and adding what causes it to bind up? Does it turn smoothly with the complete rotor head attached and ready to go but the motor not on? Or does everything turn great with the rotor head off the main shaft and the friction occurs when you put the rotor head on? Something else?

Let us know and we can probably shoot you a few ideas.

Spiro

Thanks Guys... I should be more speciffic. The shaft turns fine, it's the for/aft and L/R action at the swash plate that is stiff. I am trying to locate the problem area, ie; the mixing arms, ball links, swash plate adjustment etc. I have been exercising the movements by hand and things have loosened up some, but I'm thinking they need to move more freely. I finally got my batteries and will be ready to run up in a couple of days. I'm wondering if I should tie it down and run it up and see if things relax on their own.

Thoughts...

cb

Ok, now I got you. So the swashplate, with no linkage attached to it, swivels around just fine, but when you bolt the rotor head on and connect the linkages to the swash plate, the swashplate tilts with a lot of friction, right?

Disconnect the linkages between the swashplate and the rotor head. Make sure that each and every point of rotation or pivot in the various rotor head assembly is very very loose. It sounds like you have already done this.

Check to make sure all of the ball link shanks, plastic female parts which snap onto the ball links and thread onto the various pushrod links, rotate very freely on the balls. These are often too tight. On method is to snap the shank over a ball and squeeze the plastic around the ball with a pair of pliers. The manual says to do this gently but I have always found quite a bit of force is required to loosen the fit up. A second, possibly better, method is to put a ball on a screw and chuck the whole thing up in a drill/dremel. Snap the shank over the ball and hold on while you fire up the dremel. After a few seconds the shank should turn very freely on the ball. A surprising amount of drag can be created by all of the ball links involved in the main rotor head. These should be loose enough that they will flop straight down under their own weight and dangle freely from the ball. Of course don’t go so loose you have slop

If all the balls turn like silk in their shanks, it is time to check the lengths of the linkages between the main rotor head and the swashplate. First off is the short link between the follower arm and the subrotor. This should probably be done with the rotor off the heli, but whatever is convenient for you. Just make sure the follower arm and the subrotor are parallel. It may help to put a short metal ruler or level on the parts to make sure they are parallel. Once they are parallel, bolt the main rotor assembly onto the shaft. Snap the short follower link onto the swashplate. Now adjust the height of the main rotor shaft by loosening and moving the shaft collars above and below the main shaft bearing blocks as necessary. Adjust this height until the follower arm is parallel to the swashplate. Again, a couple of short metal straight edges may help. Once everything is lined up, secure the shaft collars. Snap the subrotor push rod ball shanks onto the swashplate. These may need length adjustment if they push down or pull up on the swashplate. They should be just long enough to hold the swashplate down in place. The instruction manual provides lengths for all of these linkages, and they are very close. I have found that sometimes the I need to adjust the length of my linkages a small amount to get everything level and to not push up or down on the swashplate too much. Sometimes the lengths can be difficult to measure accurately and these length readings are affected by how much flash may or may not be on each part.

That is about all I can think of, and ideally should give you a silky smooth setup. Most likely you have already done all of this. It has been my experience that the linkages do loosen up somewhat during the first few flights. I would recommend, as you have suggested, running a few tanks/batteries through the works without actually lifting the heli off the ground. After doing so check the linkage again. You will defiantly not want to fly with excessive drag or sloppiness in these linkages as the control will be exceedingly poor and definitely not suitable for learning. Regardless of if this is your first heli or not, I would strongly recommend building a set of training gear out of two dowel rods and some ping pong balls as the manual recommends. These are incredibly helpful in not tipping over the first couple of hops when you are getting the controls trimmed in. If this is indeed your first heli, follow the excellent flight instruction manual just as you have the building manual and don’t rush things. There are plenty of things to feel uncomfortable with and learn at each step of the process. You will be hovering around in no time.

Let us know if you get the swashplate to loosen up, or if you discover something else.

For what it is worth,
Spiro

Spiro, sometimes I get the feeling that me, you and Davidhnsocal is the only ones pushing this LMH forum here. Alot of guys are hanging out at the Ezone forum. Mabey they might let one of us moderate this forum one day cant fly today forgot to charge my xmitter last night besides that its way to windy today. guess Ill clean up the shop and do some organizing

Spiro... Thanks for the most excellent advice. I just ran her up for the first time, and I have the proverbial ear to ear smile right now. I'm at work and it's windy outside, so I took it in the studio and had a 6" hover going in a couple of minutes. I CAN"T BELIEVE HOW COOL THIS IS! One of my co-workers has one and he helped me make a couple of adjustments, but, overall it was ready to fly. I have a flaky main gear which I'm hoping LMH will replace, but evrything seems to be great. The swash plate is still a little stiff, but not nearly as bad as it was. I have to work on all of the advanced radio settings, but, in the meantime I will be hard to pry my hands off the TX. I've got a couple hundred hours in a real Bell-206, and that helps me to a degree, but there is nothing like seeing and feeling this thing lift off after all the work building it.

I'm Totally In Love!!!

Thanks for all the support... You guys are great!

wwm

Have fun, and watch out for the ceiling. It can jump down and grab you in a heartbeat

Spiro

Spiro... I also found out that the ground is no necessarily my friend. I was trying to hold a hover in the backyard and the tail rotor servo arm broke, putting the heli in a spin. I cut the throttle but I ended up with my first blade strike. I was crushed, but after hearing so many horror stories, I figure it's no bib deal. I am having a problem with my radio though. I bought the Airtronics RD 8000, and when I switch it to the heli mode, the throttle ch will not work. Granted, I have a lot to learn about the radio and, of course, fly RC heli's. I can tell you that flying a Bell Jetranger is much easier than this thing, but that's where a little patience comes in. Right.

Thanks, and if you have any radio tips, I would appreciate it.

wwm

Howdy bill, Dont use the heli mode on the radio, The Corona flies with any standard 4 channel radio. Theres no mixing of the throttle and the collective which the LMH dosent have. Use it in airplane mode. Dont mix anything. The LMH is a very basic helicopter. That was the reason for your crash(pilot error). Sorry to hear about your crash but that sounds like a quick fix. Disassemble your tail rotor shaft and run a 3/8 dowel down the tube. You can lightly tap out the dented section as you force the dowel down the tube. I have heard of people using a 3/8 steel rod to do the same just have to make sure you taper and deburr one end of the steel rod. On your servo arm thats easily replaced but also take your servo top off and inspect the gears to see if you didnt break out some teeth also. If you did, you will need to get a gear set for that servo. Youre right about flying the full size heli such as the Jet Ranger I have a little stick time under my belt also in the 206. It would probably be the same if you scaled up the wind speeds to what the Corona has to deal with. Boy would that be a ride. A dent in the tailboom is just part of the initiation into the club.

Hmm… I am wondering how the tail rotor servo arm broke. From what you saw, is there any explanation for this? If you want a somewhat beefier servo arm I suggest the Dubro Super Strength Servo Arms:

http://www.shopatron.com/product/pro...d=DUB675/101.0

They carry these at my LHS on the Dubro rack and are significantly stronger than the tiny stock horns. Just make sure you get the right ones for your servo brand. After figuring out the correct arm length, hole size, ect. I usually trim away all the extra arms or excess material to save a gram or two.

Darth has you covered on the crash repairs. I would recommend the steel rod over wood for tapping out your tail boom dents. I used a steel one for the first time last night and was very impressed with the nearly new results. You might also want to check out the mesh between the main shaft bevel gear and the tail rotor drive wire bevel gear. The tail boom has a tendency to shift around a bit when you have a “quick” landing. Just give everything the once over.

On the radio I would again agree with Darth. I have a minimally fancy computer radio that I could use if I ever decided to get some high dollar non bounceable helicopter, but I don’t see that happening any time soon. Truth be told I don’t use a single one of the “heli” features on the radio, though I find the adjustable servo travel, dual rates, and remote gyro mode selection to be very convenient. In fact Darth raises a good point. Make sure you are not using Idle Up, Throttle Hold, Hover Pitch, or any other heli mixing functions as these are not intended for use with your particular setup. Revolution Mixing can be used with a standard or “rate” gyro, but you must not use this feature if you use your gyro in a Heading Hold mode. Other than that, Hovering Throttle can be pretty useful to dial in the throttle curve the way you want it. You usually want to set this up so that your heli hovers at 1/2 throttle. I imagine your radio’s documentation has some pretty good instructions on how to setup or disable these features. If you have any specific questions on how these features relate to your heli, feel free to post them up here and let us take a crack at them.

For what it is worth,
Spiro

I fly with an Airtronics Stylus multi mod radio. I use the heli mode on my 110/117. Using this mode does not create any problems. (stay away from any throttle hold switches or settings) (If you get adventures you can use the throttle hold as a kill switch (with the correct setup)

Since you do not have a collective servo (unless you are using channel 5), collective pitch curves do nothing. Collective pitch curves adjusts the collective pitch to the throttle stick position it does not adjust the throttle. You can use revolution mixing and it does help (as long as you are not use a hh gyro. I do not know about your specific radio but on mine I also have some additional control over the throttle with a variable pot that is used for fine-tuning throttle setting to hover.

There are of course many of the heli mode settings that do not apply to the LMH (since it is fixed pitch). But, some do and can be useful.

Thanks for the information guys.

I got the radio back in the aero mode and the boom straightened out and back I went. I was working hard at the hover and a little gust swept me out of my comfort zone... I lowered the throttle but one of my training gear balls hung in the grass and over she went. I had the gyro mounted behind the MR shaft and the shelf and gyro were knocked completely off the crutch. I got everything back together, but now when I get the heli light, I have no control over the tail rotor. I've checked everything that a new guy can figure out on his own...(really don't know what I would do without all of you guys out there!) I've come to the conclusion that either the TR servo or the gyro are toast. I can move the TR servo on the bench and @ low throttle can see the blades move, so I have this gut feeling that the gyro is gone. I can see why some guys give up at this point, but I'm not one of them.

What To Do?...



wwm

Chopperbill, Youre probably right about the gyro. I hear they cant take much abuse. I heard Litemachines is suppose to come out with a new and improved mechanical gyro which is supposed to give the electronic gyros a run for their money and will even work on the Coronas. You may be able to send the gyro back to the manufacturer or place of purchase to get it fixed or replaced and mabey at no charge. But then youll have the down time to wait in order to fly again. Mabey the next time try moving the gyro up to the forward section of the crutch where it most likely would have a better survival chance in case of a mishap. I know some people have difference preferences of placement but the gyro is probably going to be the most sensitive piece of equipment on your heli.

Chopper Bill,

I assume the mechanical linkage of the tail rotor is all ok right? You might want to disconnect the tail servo pushrod from the control horn on the tail rotor gearbox and just move the horn by hand a bit to make sure everything is good.

It is also pretty easy to check to see if the servo looks good and the gyro is shot by removing the gyro from the loop. Just unplug the gyro from the receiver and servo then put the servo wire directly into the appropriate connector. Turn on your radio gear and slowly move the rudder stick back and forth. If all is well you should see the servo follow your stick motions slowly and smoothly. If there are any sticky spots, glitches, reduced travel, strange noises, or the like then you probably have messed up the servo.

Often it is possible to strip just one tooth of a servo gear and not even notice the problem. Later on down the road that tooth will most likely find its way into the rest of your servo gears and jam the whole works up at an inappropriate moment, like when you are showing off in front of the boys… Go ahead and take apart the tail rotor servo. I would do this after any crash involving the tail rotor (or that seems to affect its operation) and this only takes a few minutes. It very well could be your gyro, but a set of gears for the servo are relatively cheep and they may ALSO be messed up anyway

Take the servo off the crutch. Take the servo horn off of the servo, holding onto the horn as not to back drive the servo gears. Take the four little screws out of the bottom of the servo case. The servo case will have three sections. You can keep the bottom and middle sections together if you want by holding them between your two fingers while you pull off the top. The bottom and middle contain the motor and electronics and will need no servicing. If you want to take a peek in there feel free, just don’t tug the short wires out between the controller board and the motor. Once you have the top off you should see the gear train. There will be a “large” final gear that goes through the outer case and is normally attached to the servo horn. Pull this one off carefully trying not to send the rest of the gears flying. You will notice that this last gear fits onto its notched shaft in only one orientation. This provides the position information for the feedback loop on the controller board. All of the other gears will slide off of their shafts very easily. You can easily keep track of which gears assemble in which order in the little gear train by lining them up neatly in a row as you take them off. When all of the gears are off, take a look at each and see if there are missing teeth. Normally, if there is a problem, the teeth will shear off of the large final output gear or the one before it. If teeth are sheered off, they will be floating around in the top portion of the servo case. It is important to get all of the little bits out and have everything spic and span so debris will not jam the gears up. If all the gears look good, great start reassembling. If some are messed up, order yourself a replacement metal gear set and you will essentially never have a problem with them again. Upon reassembly just put the gears back in the reverse order you laid them out. When it is time for that final gear, make sure it lines up correctly with the little notched shaft and press it on. This is often easiest if you gently turn the notched shaft to some easily repeated 90 degree orientation to the case sides and then put the gear on over that. If the final gear does not press on, it is probably not lined up. With the last gear on hold the whole case together, being careful not to have any wires poking out of the bottom section, and put the four bottom screws back in. The whole thing will probably take about 10 minutes including time spent poking around for your own amusement. You could probably do this in 5 minutes pretty easy.

Best of luck tracking down the problem. I am sorry if it is the gyro as those things are expensive. You may want to take a good look at your gyro mounting location and see if there is a more secure solution. There may be a better place to put the gyro, or perhaps the little gyro table could be more securely attached. In any case, being able to avoid the same damage in the future would be very nice I imagine If it is any help, which I doubt, I put my gyro right where the electric guys have the electric motor. It is very protected in that corner and has never come loose in flight. Perhaps there is some other place up front that would work for your crutch.

For what it is worth,
Spiro

Do you think it's worth replacing the plastic gears in the servo's before they go on you? I have no Idea as with the little flight time I have had, all my servo's continur to work fine.

I fly plastic gears on all of mine except the tail rotor. I figured I would put in metal gears as long as I was at it the one time I stripped them. I have never stripped any of the other servo gears.

If I were to do it all over again, I would have bought all metal gear servos right up front even though it is clearly not necessary.

For what it is worth,
Spiro

Chopper Bill

I see that you have chosen to swith your radio to aero mode.
be carefull. The aero mode has mixing functions that are not compatable with helo's. e.g. aileron to elvetor, aileron to rudder.