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GrandRC . CanoMod . Futaba-RC

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e-Electric Conversions > Questions concerning "the box"
 
 
scott s.
Veteran
Location: Orange, Ca.

As i understand it the setup of THE BOX means geared for high headspeed for flying or 3d with throttle curve set to 90 or 100% in order for the speed control to be happy. I`ve heard in my limited knowledge of electrics. If you just wanted to hover you would/could? dial down the throttle curve to bring down the headspeed but this would make the speed control heat up because it`s not running at it`s maxiumum,is that right? The other way to bring down headspeed is lower the cell count,is that right? So, here`s my question, if your running 4s4p`s or 5s4p`s to have the power to do 3d but you just felt like hovering for a while then flying on what`s left in the pack how would you set up? I mean you wouldn`t start flying with the lesser cell pack to hover,land ,change packs,then go 3d with the higher pack,right?If you want less headspeed with the big packs and you dial down the curve to get it you`ll cook the speed control .Is my thinking correct on this or not? Thanks, Scott
10-31-2004 Over year old.
 
 
scott s.
Veteran
Location: Orange, Ca.

ttt
12-13-2004 Over year old.
 
 
ScotY
Senior Heliman
Location: Honolulu, HI

The "Box" is simply a 2:1 gearbox. Adding this to the typical gearing available in a glow helicopter (somewhere in the 8-9:1 range) will allow you to use a motor that is most efficient and powerful at high rpm, with a reasonable headspeed. Some motors, such as the popular Hacker series, work best while running at high rpm...somewhere in the 40,000 rpm range. You'll need about 20:1 gearing to get the rpm at the rotor to a reasonable level with this type of motor. The "Box" makes this possible.

You are correct re. the speed controller and heating issues. The more you dial back the rpm with the controller via throttle curves (or governor values), the more the controller will heat up. You can, to a reasonable extent, reduce your headspeed for hovering via the controller. The only way to really do this is to try it and see how much you can get away with. Using an bigger than necessary controller could allow you to reduce rpm more than using a "properly" sized one. You could change pack cell count to reduce rpm but that brings up all kinds of other considerations...additional costs, possible CG issues, etc.
12-13-2004 Over year old.
 
 
steph280
Key Veteran
Location: Irvine, California

The best way to understand this is to calculate based on watts, which is voltage x amperage. For example, just grabbing numbers out of air, the heli needs 1000 watts to hover. If you have a 5s battery pack, around 20 volts, you will need to pull 50 amps to hover (20x50=1000). But if you go to a smaller 4s pack at 16 volts, it now needs 62 amps to hover. The higher the amp the hotter your esc/motor/battery gets. Plus your ESC may be programmed for one pack and may have problem holding RPM on a pack of different cell count.

So it's best to stick with one pack configuration and dial down the RPM manually. Except this may not extend the run time, as most energy is simply converted to heat by the ESC, and may cook it like you said.

Making the heli lighter or adding larger packs will extend the run time. But since one contradicts the other, you'll have to find the ideal balance of weight and duration.
12-13-2004 Over year old.
 
 
rroback
Key Veteran
Location: Irvine (UCI), Ca

also, depending on the model, you may be able to just put a different pinion on, to lower your headspeed for hovering.

Rhett... There's no power like E Power!
12-13-2004 Over year old.
 
 
scott s.
Veteran
Location: Orange, Ca.

Thank you

There`s a lot of the info i was looking for. I just bought the astroflight wattmeter to aid in my learning curve. i hope this will help. has anyone used one of these?
12-26-2004 Over year old.
 
 
fitenfyr
rrProfessor
Location: Port Orchard, Washington

Electrics and headspeed

Scott,
The unfortunate downside to the boxed system is that you cannot have the best of both worlds.
The solution I have for you is to just not install the box right now.
For example I have a Logo 10.
Mikado recommends the Hacker C50-13L motor for it in the 1:1 configuration (ie not boxed) on like a 16T pinion I think.
That will give you a nice subtle helicopter capable of some mild aerobatics and good hovering on 12 Cells NiMh or something like 4s in LiPo's (just pulling things out of the air right now)
Now when you are ready to go to 3D or just want the higher headspeed you can drop in the box, stick a 20T on there and go with a 6s LiPo and you are cooking.
As you can see though this will reqiure a second battery purchase to get the High voltage you will need on the box.
Putting a smaller pinion on a boxed setup will also cause heat buildup and probably damage the system somehow.
The box is really a HV High Headspeed system no matter what.

You didn't say which helicopter?

I would recommend if you are just learning to hover on it get a couple good 12 cell NiMh packs like GP3300's or so and run it un-boxed that way.
Then you are not out much $$$ in batteries.

Check out rcgroups or logoheli for a ton of configuration ideas if you don't find them in here.

Jason Stiffey
Fly Fast....Live Slow...
12-26-2004 Over year old.
HOMEPAGE  
 
 
scott s.
Veteran
Location: Orange, Ca.

Not new to helis

Just the electric ones. Like i was saying if i just felt like hovering in the front yard without having to go to the field to 3d that would be nice without needing to have 2 battery setups or switching out motors or pinions. My intent was/might be a raptor 50 using "the box"
12-26-2004 Over year old.
 
 
steph280
Key Veteran
Location: Irvine, California

Sorry Jason, you got it all wrong.

The idea of the box is to let the motor run at its most efficient speed range, which is up to 40,000RPM, while maintaining the same headspeed. It is NOT intended to increase your heasepeed, but to maintain the same speed while increase the overall torque. If you were to run your motor straight on stock gearing, motor will probably be spinning at 15,000 RPM, which is far below it's optimal range, thus resulting in bogging and motor running hot.

I have ran Hacker 15L and 13L before without the box, and now am convering it to with the box. I also have the box on my Raptor conversion. After a 10 minutes flight the boxed motor is no more than 100F degrees, while the non-boxed motor is well abover 150F. It's pretty obvious which is the more efficient setup.
12-26-2004 Over year old.
 
 
fitenfyr
rrProfessor
Location: Port Orchard, Washington

Sorry...

Well I guess I didn't convey that well.

I agree it puts the motor in the optimum speed range with less AMP draw which means less heat and more effiecency.

What I mean is that without the box you cannot maintain the high headspeeds on those motors without possibly doing some damage as you said.

The box IS designed to get higher headspeeds on lower amps. That was the entire purpose of the gear reduction from the start.
More efficency and higher RPM's.

The torque is a result of less AMP draw and more voltage available.

You can put an outrunner on one and get more torque by the design of the motor on the same kind of voltage.

Jason Stiffey
Fly Fast....Live Slow...
12-26-2004 Over year old.
HOMEPAGE  
 
 
rroback
Key Veteran
Location: Irvine (UCI), Ca

well, actually, the torque is not really related to the amp draw.. and voltage. think of the torque in relation to bogging. quick cyclic changes of course slow the headspeed down, and if your motor, in the case of an inrunner, is spinning fast, the applied load is significanly less per revolution, hence slowing the motor less, and slowing the head less. an outrunner, by nature of a heavy bell, can use it's kinetic momentum to keep the headspeed from bogging down. you can run a inrunner efficiently at high and slow headspeed, just depends on the setup. I think your best advice is to contact Gary from Tppacks.com as he had tested just about every setup. Both Steph and I have witnessed him do it, and have gained a lot of knowledge, but he knows the setups a little better

Rhett... There's no power like E Power!
12-26-2004 Over year old.
 
 
steph280
Key Veteran
Location: Irvine, California

Here are the headspeed from my Raptor before and after being boxed:

Before box: 2100RPM
After box: 1900RPM

So no, the box is NOT to increase the HEADspeed. It is used to increase the MOTOR speed while keeping the HEADspeed constant.

My Logo flies at around 1900 RPM right now, and after the box it should be around the same headspeed eventhough I doubled the voltage.
12-26-2004 Over year old.
 
 
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e-Electric Conversions > Questions concerning "the box"
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