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Mikado Modellhubschrauber . GrandRC . CanoMod

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e-Electric Conversions > Hot Lama any ideas Guys?
 
 
Bell Bloke
Key Veteran
Location: England

Well I just woke up at 5am this morning with my Lama ready to go and I thought I just couldn’t wait for it to get light outside. So I decided to perhaps a rather recklessly, fly the Lama in my front room. Just to test it you understand. Now as you folks know there are a few of us that are converting Lamas to electric and some have gone the 3 blade head route. You will also know that all of us have heard from friends who know this bloke down the pub who’s mate knew someone that had one with a 3 bladed head on it, and said it was an absolute pig to fly neigh impossible. Well folks I'm not a bad Pilot but I would imagine that most of you are more experienced that me as I've only been at this game for 18 months now. But I have to say that when it comes to 3 bladed Lama flying its, well, easy!! As much as I would like to say it was difficult and that you have to be super human to fly this thing it's not and you don't. In fact I would go on to say that it's just about the easiest thing I've flown to date, easyer even than my Bell 47, now I thought I'd never say that because me and that chopper really understand each other!
Smooth WOW is it smooth, and so solid in the air even in my front room with all of that recirculating air it just sits there, and I haven't even set it up yet!!! I tell you guys if anybody tells you that 3 bladed heads on the Hirobo Lama 30 are hard to fly, well Bell Bloke has just flown one in his front room, half asleep and with a dodgy set-up and it was FANTASTIC!! So there!

I do have one problem Gentlemen. The Hacker C50 16XL motor and Jeti speed controller are running hotter than in the Bell 47.
1/ Because 3 blades at 550mm (the Bell is x2 at 600mm)
2/ Different gear ratio, must put taco on head and see what it's doing 1800 rpm is my guess.
3/Hover pitch I know is 6-7degrees, which I think, sounds about right.
I know it's early days and I was hovering for about 10 mins but I don't like things getting hot. The motor felt like a hot cup of tea, is that too hot?
The Li-pos seemed fine normal I would say, just barely warm.
The speed controller was very warm.
Do you think smaller blades would help? Don't really want to change gear ratio, but I will if I have to. Anyway thanks again Gentlmen for your time, I'm going back to sleep look forward to your ideas.
Here is a picture of the Lama, it's real easy to fly! But is just a little hot, maybe?



All The Best
03-13-2005 Over year old.
 
 
Bell Bloke
Key Veteran
Location: England

Hi Guys, well I think its back to the drawing board on this one. I hate to be the bearer of bad news Boyd but I don't think your Lama will work. The reason is that Hacker motor is trying to run the head at a too high rpm. Unrestrained its turning my three bladed head at 2400rpm!! That's very bad news, I know this because I've striped three main gears finding out. Quite simply I believe that main gear is giving out because the torque from that motor is so high to sustain that rpm. Because I am not used to seeing 3 blades in motion I didn't realise how high the rpm was until I put a taco on it.
If you cut the power down on the motor then the gear is fine and does not fail. The head speed is at 1500rpm and everything is good EXCEPT the temperature this is within peramiters on the motor but the speed controller temp is through the roof. The truth is it doesn't matter what you set the throttle max power at, everything still gets hot and that's no good.
What needs to happen and to be honest what has concerned me from the start when I found out you can't change the gear ratios on the Lama without ditching the clutch and a major rethink. Is that in my calculations I worked out that the headspeed would be too high, but because the Bell 47 runs so beautifully cool, cold even the same set-up would have plenty of latitude for adjustment. But I'm sorry to say this is wrong.
For this set-up to work it is my belief that the gear ratio must be lowered, otherwise it is like driving a car every where in top gear, even from standstill. However lowering the gear ratio on that Lama is much harder than you may think as the pinion gear already only has 8 teeth! You will need a pinion with 5-6 teeth to get the correct result, and that is asking for trouble. I do think that I may have a solution and will keep you posted. Any thoughts would be greatly received. It's has been a bit quiet on this post lads, have I bored you all to death? Boyd have you got yours going yet? stephanuccio, I'm on the case!
I tell you one thing though for all of the drive train problems it still flies steady as a rock, Lovely!

03-17-2005 Over year old.
 
 
fritzthecat
Key Veteran
Location: New Orleans

The speed controller gets hot because the duty cycle to drive the motor slower for 1500rpm is shorter. The excess power has to go somewhere, in this case it gets converted to heat.

The Hacker C50 16xl has a RPM/V of 1015. If you go to a C50 21xl with a RPM/V of 773 you could reduce rpm by about 25%. So your head speed should go down to 1800. Running at 85% throttle, a common number among eHelis, the head would be right around 1500 rpm.

Also you can get a small 12v cpu fan at Radio Shack and have it blow on the ESC for extra insurance. They draw 100ma at 12v - negligible for your battery.


Fritz


'Send Money, Women and Guns!'
03-17-2005 Over year old.
 
 
Hoverup
Elite Veteran
Location: Gulf Coast

Sorry for the delay in responding. I am running a Hacker B50 20XL with the lower Kv and am having no problems. I am flying on the two bladed head with the stock blades to get things sorted before I go to the three bladed conversion.

Cheers - Boyd
AMA80393
Major USAF
Retired
03-17-2005 Over year old.
 
 
Bell Bloke
Key Veteran
Location: England

Hi Boyd. Thanks fritzthecat, its just as I feared I should have looked into the available gear ratios for the Lama before I purchased the Hacker 16XL. I shall make my own gear set with more flexible ratios rather than being tied to the 1 ratio. This may seem like over complicating things at this stage but I am running very big scale sized blades so I will probably have problems down the line even if I change the motor. Will show you the results. All the best!
03-17-2005 Over year old.
 
 
Bell Bloke
Key Veteran
Location: England

Right I'm running out of time on this project, and messing around with gear ratios on that Lama is going to take too long so Fritz, I have ordered a 21XL, many thanks for that I didn't know that Hacker even did one at 750rpm per volt. Still it's my fault for not looking into Lama gear ratios a bit more. Mind you I am surprised that you can't change it as even my humble Eco 8 has all sorts of ratios available. Will keep you posted all the best.
03-19-2005 Over year old.
 
 
stephanuccio
Heliman
Location: Los Angeles

Working hard !!!

Well BellBloke, I see you have been working hard. I am so glad that I will one day benefit from your extensive trial and error process. Let me know if you need anything from me (US purchases etc...). I am not of much help to you right now but If I could become don't hesitate. I have a feeling you guys are going to make this eLama a classic. I can't wait to have the magic formula for it.
03-21-2005 Over year old.
 
 
Bell Bloke
Key Veteran
Location: England

Hi stephanuccio, well I've compounded some problems for myself here on this one. As I've said before I really didn't do enough research into Hirobo models before I went out and bought all of the electronics etc.
I just assumed than there would be the same latitude on the gear ratios as the Century. NOT SO. There is no room for manoeuvre on this issue so the motor match is more critical. Also I have not helped things by A, running 3 blades & B, running oversized scale blades. But with the new motor I'm sure it will work. Will keep you posted
03-23-2005 Over year old.
 
 
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e-Electric Conversions > Hot Lama any ideas Guys?
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