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Home✈️Aircraft🚁Helicoptere-AlignOther › Which pinion for Medusa Afterburner
07-22-2006 09:20 AM  14 years ago
3D WASP

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Your tach is wrong you only have to do the maths to see this

Unless of course your setup is so good it has no losses anywhere
Ok well I'm not ruling this out, if im only getting 2600-2700 on the head then 3100 has got to sound insane. It also must fly freaking insane. If my tach was wrong dont you think that it would read inconsistently? The latter of your quote is possible as well, everything is very free. And as I have previously said when I run Apex batteries the headspeed is considerably lower, its possible that my new TP packs got some punch. Which they do, this thing almost flies like my 4 cell. I'm almost positive these readings are correct but i'll double check tomorrow with another tach.
Timing is everything
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07-22-2006 09:33 AM  14 years ago
gorn

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Western Australia

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Well as I stated before, I have better than TP packs and Im not getting that high a headspeed and mine is all metaland very free moving as well.
Are you positive that you actually have an 11 tooth pinion?
Silly questions I know, but we all make mistakes sometimes.
Just so you know, Im not trying to flame you or anything, just that speed is definately off.
I will also retach my HS tomorrow weather permitting. I'll do a zero pitch 100% (which its not usually set at of course) and I'll do a full pitch 100% whichis what its always set at in idle 1.

Hyde...Thanks for the tip there mate, thumbs up for you
Thumbs down for you cos now i just also bought the expansion pack for Aerofly Pro, more money!! lol
For the love of the hobby
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07-22-2006 09:58 AM  14 years ago
smoothound

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Lancing, West Sussex, UK.

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3D WASP

I'm not having a go honest, I know it looks like it but I'm not

All I'm saying is assuming the Medusa kv is correct the theoretical max headspeed with no losses on a 3s Lipo pack of any quality is 3140.76rpm. However efficient your motor is and however well setup you machine is there will be losses. Not least the voltage drop on the pack just spinning the motor and then spinning the blades even at zero pitch this could give a drop of say 1v which would straight away drop your theoretical max rpm to 2866.57.

Here's how I would work mine out, others may do it differently, depends how much you allow for efficiency and voltage drop.

Medusa kv 3400 x average pack voltage 11.5v = 39100 motor rpm

Main gear 150T / Pinion 11T = 13.64

39100 / 13.64 = 2866.57

Efficiency and losses 90% x 2866.57 = 2579.91

So I'd hope to get a usable HS of around 2600 for most of my flight give or take a bit
Phil
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07-22-2006 03:30 PM  14 years ago
KamikaziRcPilot

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Cincinnati, OH

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I have a decent drill press, but I don't think that I could accurately bore out a pinion.

Thanks...
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07-22-2006 04:59 PM  14 years ago
looseblades

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ocean gate N.J. usa

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if the pinion has a set screw it, do not try and drill it the set screw hole will make the bit walk off center. i used a end mill to bore them out. they come out much better.

roy
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07-22-2006 05:05 PM  14 years ago
KamikaziRcPilot

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Cincinnati, OH

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Thanks. If I can't find one ready made, I'll stick with the 11T or 13T. Someone's bound to make one.
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07-22-2006 11:28 PM  14 years ago
KamikaziRcPilot

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Cincinnati, OH

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Hyde: Sorry that I missed your comment above. I have several projects going at once and often skim through posts when I get a few minutes.
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07-22-2006 11:35 PM  14 years ago
KamikaziRcPilot

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Cincinnati, OH

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Has it been confirmed that the pinions from Ikarus are of the proper tooth pitch (not sure if that's the right term) to ensure proper mesh as not to tear up the main gear?

Just thought I'd check before putting one on order.

Thanks...
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07-23-2006 11:30 AM  14 years ago
I3DM

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Israel

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Gotta love them Medusas !!

I run my 3400 on 4S \ 10T pinion \ 85% throttle and getting 3200 RPM headspeed in a hover.

Boy does she fly !!
www.liorzahavi.com
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07-23-2006 11:33 AM  14 years ago
3D WASP

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Ok I tached my Rex again today with my tach and it was 3120, again. I flew it for all my good packs, then I tached it using a different tach on an old tp pack, was 3090. Tached it with my tach on that battery and was 3000. I am running an 11t pinion and I am getting 3000+. Casey can vouch for me on this one. He was there and agreed it sounded like 3000 and his tach also verified mine is reading correctly. Perhaps medusa under rates the kv on there motors, in any case, 11t, 100% throttle, 325 KOK's, cc45, 3120 on brand new TP's.Timing is everything
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07-23-2006 04:52 PM  14 years ago
caseyjholmes

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Portland, Oregon

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I was standing right there. Wasp even used my Tach =) He must have flown the damn thing through 5 packs for 10 minutes each flight with non stop 3D tricks.
He sure flew the crap out of it too! Great flying Dude. You have real potential in this hobby. Some of those piro flips were looking perfect!
Interesting to see the Pro-grammable paddles after you stuck the weights in em too
I almost forgot I have the weights on my Trex450 SE flybar still, deadening response.
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07-23-2006 05:08 PM  14 years ago
smoothound

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Guess this means the Medusa kv is really nearer 4000 then...Phil
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07-23-2006 05:15 PM  14 years ago
SSN Pru

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Taxachusetts

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you sure you dont have the medusa 28X32 4200 kV motor? maybe miss labeled? thats the next higher kV rating. i have one and initially tried it in the trex but the headspeed just sounded waaaayyy too high. i never tached it but just from the sound you could tell it was way up there. i was scared of the current draw as well with that high of a kV rating.

pru
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07-23-2006 11:03 PM  14 years ago
3D WASP

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if it is miss labeled then that might be a possibility. But the motor is labeled 028-032-3400. I dont know how I do it, perhaps everything is very very free, but that's the true headspeed i'm getting. Maybe my cc45 is letting ALL the power go? Casey get your tails working and we'll meet up again, I want to see you rip it up with the 600. I got the frames together on the 4 cell with the servos mounted as of now, so next time I'll have two birds. Maybe by then I'll have those piro flips down to 5 or 10ft. Was playing in the sim and I got the inputs down for backwards inverted hurricanes, so maybe you'll see that next time as well.Timing is everything
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07-24-2006 12:56 AM  14 years ago
caseyjholmes

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Portland, Oregon

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Been workin on em all day today. I think I have everything ironed out of the little guy.

Your setup is very smooth. Spinning the rotor head felt good. As much as you fly that heli is very broken in. It wouldn't suprise me if it is very efficiant on a flight meter. He is getting very long flights with super long flight times. If I'm lucky, I'll have my 450Se tuned half as good for next time I can tell you put alot of effort in to keeping your heli running tip top shape. I do too, but all the helis I brought were either brand new or very old, and still have some bugs to iron out. I tend to have alot of heli's going at once, and I get issues now and again. this is why you should stick to that Trex that you are doing so good with. Too many helis and your head will start to spin on which one is which.
I'd imagine on a weekday I could maybe get away with a few raptor flights at that spot too, since it's just a huge grassy field. I'd like to wait for a day when there is no fun fly at the building right there though and 3D planes everywhere. We'll get that field fired up in no time
The damn grass there is too low to mow though! (but makes for an awesome flying field).
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07-24-2006 01:05 AM  14 years ago
3D WASP

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Weekdays are out of the question as far as a 50 size machine goes, waaay to many kids playing soccer. Saturdays are best, go at about 3:00 and no one will be there for some time. Only problem is how hot it is.
The damn grass there is too low to mow though!
Ahh come on we can do it! Lol prob not, would be fun to try though, of course with your machine! I'm off to fly there again here soon, as soon as this battery peaks. Gonna try out those MAH taper. Just balanced them and had to put a pound of tape on the one, I don't think they are gonna fly to good, we'll see.
Timing is everything
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07-24-2006 02:37 AM  14 years ago
rc_heli_flier

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Cumberland, Md. U.S.A.

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KamikaziRcPilot,
You can get the 12 tooth pinion at:

http://www.fxaeromodels.com/product...products_id=805

This is the 12 tooth Ikarus pinion. I have this one on my Medusa
28-32-3400 and get about 2900 headspeed with a TP 2100 pack. You will need a shorter set screw as the one that comes with it is too long and hits the motor screws. It's the same thread size as the one that comes with the heli so you can just use that one instead.
By the way, I'm using it with the Microheli main gear and it hasn't bothered the teeth on the gear after about 30 flights, so I doubt it will.
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07-24-2006 03:21 AM  14 years ago
KamikaziRcPilot

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Cincinnati, OH

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Thanks RC. I ordered two fo them last night. I have a friend that'll want one.
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07-28-2006 02:25 AM  14 years ago
KamikaziRcPilot

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Cincinnati, OH

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My 12T pinion arrived today. I'm using the Medusa 28-32-3400 with a CC35 and TP1320 3S packs. I know that the 2100 packs are prefered, but since I already have 10 of the 1320 packs and none of the 2100, I opted to start with what I have and upgrade as they need replacing.

I experimented with 11T and 13T pinions. I was shooting for a head speed of 2700. The 11T would achieve that HS but at 100% throttle. The 13T would crest 3000, but the motor and packs ran on the hot side when running at 2700. I did the calculations and decided that the 12T would probably best fit my configuration.

I installed the 12T, then purposely turned down the max + and - pitches to start with. I'm using the Eagle Tree MicroPower datalogger, and I connected it to my laptop so that I could display live data. I spooled up the heli, switched to idleup1, and noted the max amps pulled at full positive and negative collective. The 1320 packs can crank out 17A continuously, and bursts of 27A. I adjusted the pitch curve until it maxed at 18A, then headed to the field to make further adjustments.

The first flight was easy going, and I realized right away the pitch needed to be increased. So I landed and checked the max amps pulled during the flight. I can do this because I have the PowerPanel addon for the MicroPower that allows you to check lowest pack voltage, max current, max rpms, and max temp. It also shows the mAH taken out of the pack. It's a fantastic tool!

I increased the max pitch and flew again. I did this sequence until the max current registered was 21 amps. That's a value I'm happy with. I also noticed that the motor temp was about 10 degrees lower than it was on the 13T pinion, and that I'm using almost 100 mAh less per 5 minute flight.

In a nutshell, I'm pleased with the performance of the 12T pinion.
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07-28-2006 09:31 AM  14 years ago
I3DM

rrProfessor

Israel

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KamikaziRcPilot, youre not using your motors potential at 21A. you went with an extremely restrictive setup.

out a 1800-2100 20C pack and youll be pulling high amps \ high pitch angles in no time - thats where the fun begins !
www.liorzahavi.com
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Home✈️Aircraft🚁Helicoptere-AlignOther › Which pinion for Medusa Afterburner
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