Recently in Servos Category

I was trying to decide which servo to use in my project. I had some JR NES-241s lying around from my JR radio kit. They are nice analog servos.

I also had some E-sky EK2-508 digital servos which I had also just ordered.

I wanted to see what the speed difference might be between the two. The JR is rated at 0.23 / 60° arc while the E-sky is rated at 0.10 / 60°. But there are ratings and there are ratings.

So I fired up my servo tester and pitted them head to head in this very short video (1 minute; 5 mb). As you can see, the E-sky is considerably faster.

The e-sky is only rated to 1.0 kg / cm torque while the JR has 1.3 kg/cm. But I think that difference is negligible.

Picture 2.png
P1040184.MP4

Micro servos are commonly used in 250 and 450 size micro rc helicopters. Here's a little table that I'm using to compare various options.

ModelModeSizeWgtSpeed@5VPower@5VSpeed@6VGearsStreet
HTX900Analog21.0x12.0x22.0mm9.0g0.12 sec/60°1.6kg/cm0.11secNylon$4
Towerpro SG90Analog21.0x11.5x27.0mm9.0g0.12 sec/60°1.2kg/cmYesNylon$5
E-sky EK2-0508Digital22.8x11.5x20.8mm7.5g0.10 sec/60°1.0kg/cmYesNylon$10
Towerpro MG90Analog23.0x12.2x29.0mm14.0g0.11 sec/60°2.2kg/cm0.10 secMetal$12
E-flite S75Analog23.0x12.0x24.0mm7.5g0.12 sec/60°1.17kg/cmNoNylon$14
Spektrum DSP75Analog23.0x12.0x24.0mm7.5g0.11 sec/60°1.17kg/cmNoNylon$20
Futaba S3114Analog21.8x11.0x19.8mm7.8g0.10 sec/60°1.5kg/cm0.09secNylon$15
Power HD-2216HBDigital22.8x12.0x25.4mm13.6g0.13sec/60°1.8kg/cmYesMetal$20
Align DS410Digital22.8x12.0x25.4mm12.7g0.13 sec/60°1.8kg/cm0.09secMetal/Plastic$26
JR NES-241Analog21.5x11.5x22.0mm9.0g0.23 sec/60°1.3kg/cmYesPlastic$30
JR DS290GDigital21.0x11.0x21.0mm7.0g0.08 sec/60°0.9kg/cm0.07 secNylon$35
Futaba S3154Digital21.8x11.0x19.8mm7.8g0.10 sec/60°1.5kg/cm0.09secNylon$35
Ino-Lab HG-D202MGDigital23.0x11.4x24.1mm9.8g0.16 sec/60°2.5kg/cm0.13 secMetal$35
Align DS410MDigital22.8x12.0x25.4mm13.5g0.13 sec/60°1.8kg/cm0.09secMetal$37
HiTec HS-65MGAnalog24.0x12.0x24.0mm11.2g0.16 sec/60°1.6kg/cm0.13secMetal$37
HiTec HS-5065MGDigital23.6x11.6x24.0mm11.9g0.14 sec/60°1.8kg/cm0.11secMetal$47

The conversion for torque from kg/cm to oz/in is to multiply by 14.7. So a servo with a torque of 1.0 kg/cm has an imperial torque of 14.7 oz/in.

Mini-Servos

ModelModeSizeWgtSpeed@5VPower@5VSpeed@6VGearsStreet
Futaba S9257Digital36.0x15.0x29.0mm26g0.08 sec/60°2.0kg/cmNoNylon$60

Mini servos are commonly used in 500 size helicopters such as the Align T-Rex 500. Here's a little table that I'm using to compare various options.







ModelModeSizeWgtSpeed@5VPower@5VSpeed@6VGearsStreet
GWS HPXAnalog35x16x31mm19g0.07 sec/60°3.0kg/cm0.05 sec/60°Plastic$13
GWS HPX F0.10 sec/60°4.2kg/cm0.08 sec/60°$13
TowerPro MG930Digital36.2x15.2x28.7 mm26g0.14sec/60°3.6 kg/cm0.11 sec/60°Metal$16
Hitec HS-225BB Analog32.4x16.8x30.8mm27g0.14 sec/60°3.9kg/cm0.11 sec/60°Nylon$20
Hitec HS-225MG 31gMetal$30
Hitec HS-5245MG Digital32.0x17.0x31.0mm32g0.15 sec/60°4.4kg/cm0.12 sec/60°Metal$48
Align DS510Digital35x15x29.2mm26g0.13 sec/60°3.7kg/cm0.11 sec/60°Metal$50
MKS DS9660Digital35.0x18.0x28.0mm35g0.13 sec/60°3.7 kg/cm0.10 sec/60°Metal$57
Futaba S9650Digital36.0x15.0x29.0mm26g0.14 sec/60°3.6kg/cm0.11 sec/60°Nylon$65

The conversion for torque from kg/cm to oz/in is to multiply by 14.7. So a servo with a torque of 1.0 kg/cm has an imperial torque of 14.7 oz/in.

Standard servos are used in larger helicopters -- 600 size electrics or nitros. Here's a little table that I'm using to compare various options.

ModelModeSizeWgtSpeed@5VPower@5VSpeed@6VGearsStreet
TowerPro SG5010Analog40.0x19.0x43.0 mm39g0.14sec/60°8 kg/cm0.11secNylon$8
Hextronik HX12K
TowerPro MG995
Analog40.7x19.7x42.9 mm55g0.16 sec/60°10 kg/cm0.13secMetal$8
Hitec HS-322HDAnalog41.0x20.0x37.0mm43g0.19 sec/60°3.0kg/cm0.15secKarbonite$10
Bluebird BMS-621Analog40.5x20.0x38.5 mm41g0.13sec/60°6 kg/cm0.10secPlastic$15
Scanner RC SSV-9764MGAnalog40.5x20.0x38.5mm62g0.16 sec/60°9.6kg/cmYesMetal$18
Futaba S3001Analog41.0x20.0x35.0mm45.1g0.28 sec/60°xxkg/cmYesNylon$20
Futaba S3004Analog41.0x20.0x36.0mm37.20.23 sec/60°xxkg/cmYesNylon$20
JR DS821Analog38.0x18.0x37.0mm43g0.19 sec/60°5.1kg/cmYesComposite$30
Futaba S9257Digital36.0x15.0x29.0mm26g0.08 sec/60°2.0kg/cmNo! No!Nylon$55
Futaba S9650Digital36.0x15.0x29.0mm26g0.14 sec/60°3.6kg/cm0.11 sec/60°Nylon$65
Ino-lab HG-D751MGDigital
Coreless
39.5x19.5x36.8mm54g0.14 sec/60°11.2kg/cm0.11 sec/60°Metal$80
Ino-lab HG-D760HB48g0.10 sec/60°6.8kg/cm0.08 sec/60°Carbonite
+ Metal
$70
Ino-lab HG-D760MG52g0.09 sec/60°9.6kg/cm0.xx sec/60°Metal$75
Hitec HS-965MG Analog40.0x20.0x37.0mm62g0.13 sec/60°7.4kg/cm0.10 sec/60°Metal$70
Hitec HS-985MG Analog39.4x20.0x37.8mm62g0.16 sec/60°9.6kg/cmYesMetal$70
Futaba S9402Analog41.0x20.0x38.0mm55g0.13 sec/60°6.4kg/cmYesMetal$75
Futaba S9252Digital40x20x37mm50g0.14 sec/60°6.6kg/cmNo! No!Nylon$85

The conversion for torque from kg/cm to oz/in is to multiply by 14.7. So a servo with a torque of 1.0 kg/cm has an imperial torque of 14.7 oz/in.

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