does a NEU 1915 engine fit in a razor ??

[bathmagic]

anyone know ?

thanks Dale

[bathmagic]

no one got any idea ?

Dale

[mudbogger2]

The 1915 will fit in the razor. The 1.5 or 1y would probably be the best choice.
Gearing will need to be chosen according to what battery setup you will be running and what headspeeds you are aiming for as well as what type of flying you will be doing.

[Taipan]

Let's say the setup is the following;

Neu 1915/1Y 684KV
CC 85HV
FP 10S 3700
Desired HS 2100-2200

For gearing, KV (684) x Voltage (37) x 0.75 (Gov mode 75%) = 18981rpm on motor.

The closest gearing available to suit would be 8.72:1.

18981 / 8.72 = 2177rpm.

Is that correct?? Or is that gearing too small? Cos on flat 100% throttle it would need around 12:1 which isn't available.

[mudbogger2]

This post has some info in the gear ratios that can be used on the razor.
http://www.helifreak.com/viewtopic.php?t=18199

I don't the the 10s pack will fit in the razor and still balance out. 2- 5s packs fit nicely.
I also do not think the 1915 is a great choice of motors IMO.

[Taipan]

Thanks. I meant 2x 5S packs.

Why is the 1915 not a good choice?

[TomC]

Taipan,

The first thing you should do is to take the time to read the Razor power systems guide;

http://www.miniatureaircraftusa.com/Support/Instructions/xcell_razor_600e_power_systems_guide_current.pdf

This is a very good report and gives you lots of info about how to calc gear ratio's.

The stock 10s ratio for a MA power package with a Neu 1515/2y motor is 18.46:1. this should give a gov'd hs ~2200, with lots of 3D punch for ~5min runtimes. If you went with a Neu 1915/1Y you would need ~ 11.5:1 ratio.

One disadvantage with the 1915 is that it weighs 2 oz, or ~60g more than the 1515 motor. The higher kv 1515 motor will also have a bit more punch than the 1915 motor. The 1915 motor is ~$US70 less than the 1515, so I guess you get what you pay for.

If you are happy with 2100 gov'd hs, then the Tango 45-08 and Jazz 55 esc power package (with ~14.25: ratio) is much more efficient and will give you longer runtimes (6-7 min) and cooler motor and battery temps imop.

A local flyer/friend is running this motor at 2100 gov'd hs (with a CC HV85, but personally I think it would run cooler with a Jazz 55 esc) on a razor and it fly's great and has lots of stump pulling power, easily more than a Raptor 50 with hyper motor.

Lots of motor/esc/ratio choices with this heli so make a good informed one, go for it, and have fun!

Cheers,

Tom C

[MrMel]

Ive run the 1915/1.5Y in a .90 sized machine, it packs ALOT of torque, however, that said, its also the "older-generation" of Neu motors, meaning it will run pretty hot and it has a chance of shaft slipping (even the newer with fan)
That was exactly what happened with mine.



The stock 10s ratio for a MA power package with a Neu 1515/2y motor is 18.46:1. this should give a gov'd hs ~2200, with lots of 3D punch for ~5min runtimes


Tom,
when you are doing your calculation you are calculating with 3.7v right?
To get really good performance you need to calculate with voltage under load, else you will get ALOT of bogging.

Gear up 200-300 RPM more and see extreme performance improvement.
(they mention this in that folder you posted)

So if you are aiming for 2200, gear up to 2400-2500.
That way, when the battery drop from 3.7v to 3.2-3.3 volt, you have room to cover up that drop.

[TomC]

Mel,

The MA power system guide uses 3.9v/cell to calc max hs's. This is because most of the new +20C cells are delivering ~3.9v/cell under load. I use 3.8v/cell in my calcs. I personnally do not see voltage drops of 3.2-3.3 with new gen +20C Evo20 packs. Lowest min voltage under load I've seen is ~3.45-3.5 v/cell at very short max power spikes of ~2200 watts.

MA then suggest you use 200 rpm as gov'd headroom, which seems about right.

Mel, I guess you need to use whatever works best for the cells you are using, but in general, the MA recomendations are very good imop.

Cheers,

Tom C

[MrMel]

The MA power system guide uses 3.9v/cell to calc max hs's. This is because most of the new +20C cells are delivering ~3.9v/cell under load. I use 3.8v/cell in my calcs. I personnally do not see voltage drops of 3.2-3.3 with new gen +20C Evo20 packs. Lowest min voltage under load I've seen is ~3.45-3.5 v/cell at very short max power spikes of ~2200 watts.


2200 watt for a 10s/Razor setup is nothing (watt/lb).

Do you have a FDR chart?
Im running only FP 20/25C, TP Extremes 25C, they sure have higher nominal (3.8), but still hit 3.2-3.3 under 17-20C load. (0.5v-0.6v drop).
I have 8 flightpower 10s and 2 TP, all act around the same .

[TomC]

Mel,

No FDR just on-board wattsup meter. If you are pulling much higher watts (say, 2500-3000 watts) then I'm sure you are right and you will see these lower cell voltages.

Cheers,

Tom C

[MrMel]

No FDR just on-board wattsup meter. If you are pulling much higher watts (say, 2500-3000 watts) then I'm sure you are right and you will see these lower cell voltages.


Ok, just a heads-up, both my Wattsup are showing volt wrong, check with a DVM to verify so you know if you need to adjust or not. (even eagletree fdr sometimes is wrong, but that one has a built in calibration tool)

- Fredrik

[TomC]

All my 10s evo20 packs read ~41.91-41.95v within 1 day after charging so this seems about right. Just in case, I'll check this with a voltmeter. Thanks for the heads-up.

Cheers,

Tom C