LMH Helicopter Discussion of all LMH helicopters both electric and glow.

Lite Machines CP help

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Old 03-06-2002, 10:49 PM
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rupert14
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Default Lite Machines CP help

I have a lite machines 110 and it is a great heli. The guy at my local hobby shop told me that he has seen one that had been modified to CP. Does anyone out there know a website or have any ideas on how that would be done? I also don't know of any LMH upgrade websites. Any info would be of great help.

Thanks,
Bob
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Old 03-07-2002, 01:03 AM
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Default Lite Machines CP help

what is a cp? collective pitch??
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Old 03-07-2002, 01:40 AM
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Default Lite Machines CP help

Yeap, I am looking for a way to make my LMH a collective pitch like all the larger helis. Hope there was not too much confusion.

Bob
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Old 03-14-2002, 04:39 AM
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maxman
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Default lmh cp

I converted my Lite Machine to collective pitch, perhaps it is the one you heard about. Collective pitch really makes this machine fly great. First, it allows the engine to run at a constant speed and in its best mixture zone as the Norvel .061 goes rich and bogs down at lower throttle settings. My machine has a constant head speed of 2000 rpm allowing the engine to stay leaned out with great power and linear response. Second, because collective pitch gives me instant thrust control from the rotor precise hovering and flying is now possible. In fact, this has become my favorite high-wind helicopter and I have flown it in winds over 20mph and have a blast doing so. Other benefits are a constant tail rotor speed with better holding power (I have removed the Altron gyro and replaced it with a heading-hold gyro) and crisper cyclic response.
Basically the cp conversion is like a Kalt system as the swashplate does not rise and fall for collective input but uses a sliding washout base. At one time there were plans on the internet that showed a cp system, but mine differes from that as I have a fifth servo for the cp and was able to fit thrust bearings in the head. If there is any interest I may post some pics later.
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Old 03-15-2002, 04:42 PM
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Default CP LMH

I am very very interested. Any pics or links to places I can get more info would be greatly appreciated. I will even pay you to help me build one if that is ok.

Bob
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Old 03-16-2002, 12:03 AM
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maxman
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Default lmh cp

I will post some pictures shortly, then. Rupert14 you mention that someone at your local hobby shop had seen a cp LMH. What is the hobby shops name and location?
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Old 03-16-2002, 03:23 PM
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Default Lite Machines CP help

The hobby shop is Warrick hobbies in Davie, FL. The guy that said he had seen one is Jim. I don't know his last name. He said he had seen it on the internet. Any info would be really appreciated.

Thanks,
Bob
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Old 03-16-2002, 04:55 PM
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Default Lite Machines CP help

Bob, There are some drawing showing collective pitch modification on

http://www.juggernauthobbies.iwarp.com/main.html

For what it's worth - Al
http://www.rchelibase.com
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Old 03-17-2002, 07:52 AM
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maxman
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Default lmh cp

Ok, here is a link to the pics but first a warning. Doing any type of modification to a helicopter, even a small one such as the Lite Machine, can be dangerous and especially changing the machine to collective pitch which involves cutting the feathering plate in half. If not done properly a rotorblade could be thrown off, striking someone with serious results. Any such helicopter should be considered EXPERIMENTAL. These pictures and any information I give are what I did to MY MACHINE, so anything you do to yours is at your own risk.

Now, having said that I just returned from a very fun day of LMH flying.
Feel free to ask any questions, I will try to answer them.

the pics: http://www.pbase.com/maxman/inbox
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Old 07-15-2002, 02:38 AM
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Default Lite Machines CP help

bump
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Old 07-16-2002, 08:36 PM
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Default Lite Machines CP help

Man! That's the best looking CP setup I've seen yet! Have you tried to fly it inverted? What parts did you have to make for the upgrade? I would like to upgrade my Corona!
-Stephen
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Old 07-16-2002, 11:48 PM
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maxman
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Default Lite Machines CP help

I have tried some loops and rolls with it but there is just not enough cyclic authority to pull it through the maneuvers and it gets very unstable when near inverted. On one loop attempt I did manage to get it completely around but the helicopter hit the ground at the very bottom of the loop, bounced back into the air still running and I finished flying until the fuel tank was dry. That was one of the most funniest things I have ever seen a helicopter do.
As an experiment to increase the Lite Machines aerobatic ability I removed the subrotor and made it into a flybarless head but on my one and only test flight it was VERY unstable and VERY quick to respond to cyclic input. Needless to say I VERY quickly put the subrotor back on. For areobatics I will stay with my Fury or Raptor 60.
Every single part in the collective pitch conversion I machined myself. I did download some plans off the internet but changed most everything as I had issues with how this person had done things. Even though I used a milling machine to make some of the parts I believe that others with basic hand tools and a drill press could build their own cp conversion.
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Old 07-17-2002, 08:20 AM
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Joe K
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Default CP LMH

I have also wanted to make the switch.
LOVE THE Photos! GOOD JOB!
Can you give any more detail on how the sliders on the shaft were made? did you use bearings of any sort?
Parts made or modified from other parts? or other helis parts?
Or were did you get the raw material?
Joe
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Old 07-17-2002, 08:51 AM
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Joe K
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Default CP LMH

How do these parts hold up in a crash?
I know the best thing I did was to replace the mechanical gyro.
It was the first to come apart or break, and the first to ware out.
Joe
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Old 07-17-2002, 10:29 PM
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maxman
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Default Lite Machines CP help

Most of the parts are made from music wire and brass tubing found at my local hobby shop. The main shaft is made from 5/32" music wire into which I cut two slots with a Dremel abrasive disk. Each slot is just deep enough for a .032 wire and these two wires slide together to move the washout base for collective pitch control. Use two smaller wires on each side of the shaft and not one larger wire on just one side, I tried that and it doesn't work well. The slider directly above the lower bearing block and worked by the collective servo is a modified JR tailrotor pitch slider, which has two ball bearings. The hole going through the brass sleeve in the slider must be reduced in size as it is larger than 5/32, I machined a new brass sleeve for mine but a piece of brass tubing could be JB Welded into place, instead.
The thrust bearings in the head are tail rotor thrust bearings from some Hirobo machine, Shuttle I think.
The 1/8" wheel collars are Carl Goldberg STEEL wheel collars, and each set screw has it's own flat. Use caution here as the collars take the centrifugal load of the blade but in my testing ONE collar can take several times the load even at 2000 rpm head speed.
Since adding the collective pitch I have only had three contacts with the ground and the only damage that I had was stripped servo gears. With the greatly added control the cp gives it's far less likely to crash, anyway.
One other note: The LMH is unique for a fixed pitch helicopter in that it has Bell/Hiller mixing, ie. it has cyclic input not only through the subrotor (flybar) but directly from the swashplate as well. There is a simpler way to make the LMH collective pitch without making a washout unit and only have cyclic control thought the subrotor but while it is very stable it also has a very slow and weak cyclic response. It needs the washout unit.
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