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Old Feb 08, 2003, 11:39 AM
Indy3D flyer
westside of Indianapolis IN
Joined Jan 2003
249 Posts
Hawk sport e conversion info

I have several nitro helis and would like to try to convert my Hawk Sport to e power. The mechanics of the conversion aren't any problem for me. The electronics are the questionable parts. I want the heli to remain fully aerobatic so that calls for a heli specific esc preferably with a governor capability. I am assuming for a heli this size I'll have to go to a brushless motor. I need to get an idea of motor power required and amp draw needed to give the flight performance I want. If someone has done a 30 size heli e conversion, can you give motor recommendations and performance comparisons. Performance of the heli with it's current OS 32 would be the bare minimum I'd want. Any less power wouldn't be worth the conversion.
Thanks,,,basmntdweller
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Old Feb 08, 2003, 11:57 AM
2013 GRAND SPORT CORVETTE
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Quite a few threads on this conversion if you use the Search engine here. You'll have some reading ahead of you. Hope this helps.
Cheers - Boyd
AMA 80393
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Old Feb 09, 2003, 01:40 AM
Our Daddy and Heli Junkie
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Sent you a PM.

What you want is within reach easy with current tech.

It just takes $
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Old Feb 09, 2003, 01:46 AM
Our Daddy and Heli Junkie
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Hawk Conversion Links;

http://www.rcgroups.com/forums/searc...der=descending
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Old Feb 09, 2003, 11:59 AM
Indy3D flyer
westside of Indianapolis IN
Joined Jan 2003
249 Posts
Since I am thinking of using Lipo's I was thinking that using a motor at higher voltage than what most are using that way I can keep a decent watt/lb ratio and keep the current lower. I was thinking of using 8s and 3p or 4p to get sufficient current. This would be about 29v nominal and approximately 35v maxed. I believe there is a Hacker controller that can handle this voltage. figuring on 30v and maxing out about 80 watts/lb gives a total of 560 watts or about 18 amp current. With a stock gear ratio on the Hawk of about 9.76 and head speed of 1850, I would need a motor rated about 600 rpm/volt. I can find lots of motors that are rated around this number. How can I tell if it will have the needed torque and can handle the voltage and amperage I want to put through it?
Thanks,,,basmntdweller
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Old Feb 09, 2003, 01:48 PM
A man with too many toys
United States
Joined Feb 2001
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A Hacker B50-25XL or B50-26XL will provide lots of power. Their Kv is 630 and 607.


If you buy the heli version you get a nice heat sink. The heat sink is also available separately for non-heli Hacker and other brands.
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Last edited by RC Man; Feb 10, 2003 at 05:19 PM.
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Old Feb 09, 2003, 05:14 PM
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Bdweller: I think your estimate of 80 watts/pound is too low. For max collective without loss of rpm it's more like 144 watts/pound.
Of course that's only done briefly, usually. Hovering takes about 50 watts/pound.

Hank
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Old Feb 10, 2003, 04:00 PM
Indy3D flyer
westside of Indianapolis IN
Joined Jan 2003
249 Posts
Thanks for the info on max wattage Hank. I was guessing that if it took only 50 at hover 80 would have been plenty for full aerobatics. That changes my numbers quite a bit. Is my thinking sound as far as running higher voltage and lower amps? I know my buddy runs his Joker on 32 cells and it works well. I was just trying to reduce the current draw to make Lipo's feasible.
Recalculating for 144 watts/lb, gives me 34 amps at 30 volts. Using 3300 Lipo cells I'd have to use 8s2p. That's about a $400 pack. That cost makes this no fun. I'd rather stay with the OS.
Going back to what someone else had done, They used 16 cell Nimh and a Mega 22/45/3. That is more in my price range but what is the wattage available there? I don't know possible discharge rates for Nimh.
Thanks,,,basmntdweller
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Old Feb 10, 2003, 06:20 PM
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Bdweller: I asked JJ Hong (from KoKam) in the battery forum about maximum power from Li-Po without damage for 3 seconds but he didn't have an answer.

The maximum power you can get from a couple of common SC cells are 53 watts from an RC2400 (Sanyo NiCad) and 68 watts from HR2600 (Sanyo NiMH). These are extrapolations from published discharge curves. I think the HR2600 may be a little high although it holds its voltage better at high discharge rates than the RC2400's do.

These kinds of power levels are abusive to cells but they seem to stand them for short periods (I assume about 3 seconds).

To get the max power from a cell you have to pull its voltage to 1/2 nominal. I presume that would be about 1.75 volts for a Li-Po. I'd like somebody to measure that because I don't have the equipment (or the cells) to do so.

Hank
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Old Feb 10, 2003, 06:40 PM
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I think 100 watts/lb is fine, but I don't do 3D.

A Tango 45-6 would work good for the LP setup and likes higher V.

Looking at a new pinion too, with a smaller pinion.
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Old Feb 10, 2003, 07:38 PM
Indy3D flyer
westside of Indianapolis IN
Joined Jan 2003
249 Posts
I'm just starting in 3D with my hawk. It doesn't really have the power with the OS 32 but it just makes you work harder and pay more attention to what the heli is doing. I just don't want to spend a bunch of money to do the conversion and end up with a "hover queen".
Right now the cost of Lipo packs is my biggest concern. Whatever motor and controller I'd end up with isn't near as big a concern as the cost of the batteries.
Thanks,,,basmntdweller
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Old Feb 10, 2003, 09:08 PM
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Jason can give you more details on the Thunder Power packs. I believe the one he used was a 7S4P 7800mah 25.2v pre built pack. (twenty eight 1950 mah cells) [not Kokam]

7.8a x 25.2v = 196.56 amp hours or 11,793.6 amp minutes

if you use up the pack in 15 minutes (4C) that would provide 786.24 per minuite or 1.069 horsepower.

Of course this is with 100% effeciency.

Brad
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Old Feb 11, 2003, 02:50 PM
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Another way of looking at that pack is to see what is being asked of it at full collective (no rpm loss). For a typical 30 sized e-conversion weighing in at 7.5 pounds that would be about 1080 watts (at 144 watts per pound). If the voltage of the pack remains at 25.2 (a big if), the amperage required would be about 43. That's a little more than 5C. Can that pack put out that much for a short period without damage? Probably.

Hank
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