RunRyder RC
 7  Topic Subscribe
WATCH
 3 pages [ <<    <    ( 1 )     2      3     NEXT    >> ] 2260 views POST REPLY
Scorpion Power Scorpion Power
HelicopterMain Discussion › 7.4V system - is it safe?
07-13-2008 09:54 AM  9 years agoPost 1
ofir

rrApprentice

tel aviv - israel

My Posts: All  Forum  Topic

For my new N9 () - I bought 8717 servos and the all in one AR7100R receiver that runs them directly on 7.4V.
a friend of mine told me that he burned some 8717
running them on 7.4V (he's a wobbling freak).

I thought about using a power diode to step down the total voltage in 0.7V just to be on the safe side.

Need some advice.

--------------------------------------------------

My name is Ofir and I am a helicopters addict...

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 10:08 AM  9 years agoPost 2
Dood

rrProfessor

Wescanson

My Posts: All  Forum  Topic

taken directly from JR's website.

Notice it doesnt say anything about 8V (7,4v), therefore it is not rated for such voltage.

.07 sec/60° and 196 oz/in @ 6V... That isn't enough?

  ▲
▲ ▲

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 11:44 AM  9 years agoPost 3
Footey

rrKey Veteran

Hamilton New Zealand

My Posts: All  Forum  Topic

I have the 8717 running on two cell LiPo in my 600 and 700 T-Rex, lost count on how many flights now and have had no problems.

I have sold quite a few to guys doiing the same and hav not had anyone say they have had trouble.

I have seen a video of Alan Szaba saying he is using the 8717 off the 2S LiPo as well

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 11:53 AM  9 years agoPost 4
JAGNZ

rrProfessor

Auckland, New Zealand

My Posts: All  Forum  Topic

The specs do not support it but a TON of anecdotal evidence does. Do it at your own risk of course and these are the only servos I would try it with...


Jason Greenwood

www.3dheli.co.nz

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 12:07 PM  9 years agoPost 5
bosshoss

rrVeteran

Chicago, IL

My Posts: All  Forum  Topic

I know,for sure, I would do a an amp draw test at full load , just to see if they pass the smoke test. Because at full pop lock to lock, the current spike might be the killer.

At least that is what runs through my mind. Just to know the numbers, and to make an informed decision.

Now, why do you need faster than .07 ???? No , don't say it, I understand. LOL.

Why Hover a Yak, when a Heli does it better?

PM  EMAIL  HOMEPAGE  Attn:RR
07-13-2008 02:40 PM  9 years agoPost 6
Yug

rrMaster

UK. Herts

My Posts: All  Forum  Topic

Peak current for the 8717 is a little over 2 amps

Vegetable rights and Peace

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 02:59 PM  9 years agoPost 7
RyanW

rrKey Veteran

Edmond, Oklahoma

My Posts: All  Forum  Topic

3.5 Amps for stalled 8717.

Look into the Lithium Phosphate cells. They discharge at a constant 6.6v without a regulator.

-Ryan

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 03:07 PM  9 years agoPost 8
ofir

rrApprentice

tel aviv - israel

My Posts: All  Forum  Topic

Look into the Lithium Phosphate cells. They discharge at a constant 6.6v without a regulator.
That sounds cool. - where can I get it?

My name is Ofir and I am a helicopters addict...

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 03:16 PM  9 years agoPost 9
BJames111

rrElite Veteran

San Diego, California

My Posts: All  Forum  Topic

FWIW, the servos will not be warranted if they fail at a voltage higher than 6V. They're crazy fast at 6v, I'd just run them there.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 03:46 PM  9 years agoPost 10
Dood

rrProfessor

Wescanson

My Posts: All  Forum  Topic

The only benefit I see in running sans-regulator is a slightly lighter, neater set up.

This may surprise you!


8717 setup

8717 weight: 2.36 ounces
4 8717's: 9.44 ounces
_____________________
Total: 9.44 ounces

Futaba Setup w/ regulator
Futaba 9452 weight: 1.76 ounces
4 9452's: 7.04 ounces
Fromeco Arizona regulator: 1.76 ounces (based on 50 grams advertised weight)
___________________________________
Total: 8.8 ounces


Cost (based on MSRP)

JR 8717: $109 (4 @ $436)
Fut 9452: $79 (4 @ $316)
________________________
Savings: $30 (4 @ $120)
-voltage regulator ($50)

Total savings (with regulator): $70

So, what that boils down to, is the hot 8717 setup is a half ounce heavier and $70 more expensive.
Is .07sec and 200oz of torque not enough for some reason?

Or if you have something like Futaba 9452's,
0.11sec/128oz not good enough?

For me, .11 and 128oz is plenty for me.
Keep in mind, that was the "hot setup" just a year ago!!

  ▲
▲ ▲

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 04:36 PM  9 years agoPost 11
Wingman77

rrProfessor

Pulaski Tennessee

My Posts: All  Forum  Topic

I kinda like that .05 sec and 250 in oz on 8v better

I run mine on 8v and I did a very rough test with them on the ground working them hard the cases got very warm and I was pulling 7 amps with three servos for a few mins. they never missed a beat and I have a lot of flights on that thing
I saw a stratus 90 go down with 8717 servos earlier this year because the regulator fried. these things pull a serius load. the regulator is just another failure point.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 05:03 PM  9 years agoPost 12
ZR2Chevy22

rrApprentice

Kemah, TX

My Posts: All  Forum  Topic

That's why you get a good regulator. The MPI regulator can handle 10amps continuous and a max of 20amps for one minute. I don't see it being a failure point.

Andrew

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 05:21 PM  9 years agoPost 13
pavan_mex

rrApprentice

Leon, Mexico

My Posts: All  Forum  Topic

QUOTE: .07 sec/60° and 196 oz/in @ 6V... That isn't enough?
____________________________________________________________

Very well said!!!

All that 8V will do for 99.99999% of us is make us add more Exponential and Dual Rates.

The rest 0.00001% are bull****ters!!

You can get a 100Amp relugator and spend $999.00 to buy it... will your receiver chip handle it???? You need something like the reactor to start off in the first place.

Not even Alan Szabo can fly like he does.(smooth and nice) with 8717s at zero Expo...at 6V

So many years wasted on plankers...!!!!

PM  EMAIL  Attn:RR
07-13-2008 05:26 PM  9 years agoPost 14
RCMed-x

rrVeteran

westpalmbeachflorida usa

My Posts: All  Forum  Topic

I have 8717s in all my birds strait from 7.4 LIon & lipo crashed ,fly hard and never had a problem . It has been over 7 months and not one failure I fly every weekend at least 2 gallons of fuel
Look in my gallery
I run 0 expo and on 8V set up 8717 run smooth .

A good teacher is a good listening student !

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 05:45 PM  9 years agoPost 15
Wingman77

rrProfessor

Pulaski Tennessee

My Posts: All  Forum  Topic

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 09:02 PM  9 years agoPost 16
ofir

rrApprentice

tel aviv - israel

My Posts: All  Forum  Topic

This is the perfect Regulator for running DS8717’s on 6V

My name is Ofir and I am a helicopters addict...

PM  EMAIL  GALLERY  Attn:RR
07-13-2008 09:26 PM  9 years agoPost 17
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

Why not run the system on A123 cells - 6.4V ?

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 09:29 PM  9 years agoPost 18
Wingman77

rrProfessor

Pulaski Tennessee

My Posts: All  Forum  Topic

airwolfrc

hm, that is a good idea...what is the voltage per cell of a123 batts?

it would be heavier though

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 09:32 PM  9 years agoPost 19
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

The A123 energy density is about half way bwetween NiMhHd and LiPo.
They are lithium iron nano phosphate (LiFePO4)
The voltage per cell is 3.2V vs 3.8 for LiPo
They can be had in 1100mah and 2300mah sizes.
They can be recharged in 10 minutes.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
07-13-2008 10:09 PM  9 years agoPost 20
Mike Fortin

rrElite Veteran

USA

My Posts: All  Forum  Topic

The 8717 servos can be run on 8V, they have been for well over 1 year now worldwide.

This is why Spektrum has released the 7100 series of Recivers with built in regulators to compliment those pilots running 8V systems.

Although it doesn't say it on the packaging, it is safe to run the servos on 8V. Horizon is fully aware that te majority of people running 8717's have them simply because of the fact that you can run them on 8v.

Also, the Spektrum RX's can all handle up to 14 volts.

IMHO te 8717's are unbeatable by any other servo on the market and have become the industry standard for what helicopter servos should be.

I don't run 4 8717's, I run 3 as I feel it's a bit overkill to have such a fast and powerful servo on your throttle.

I have been running Hitec HS81's on throttle at 8 volts for over 1 year now with 0 issues. This saves the weight of the larger servos and still gives the same performance.

Have Rotors, Will Fly!

PM  EMAIL  GALLERY  Attn:RR
WATCH
 3 pages [ <<    <    ( 1 )     2      3     NEXT    >> ] 2260 views POST REPLY
Scorpion Power Scorpion Power
HelicopterMain Discussion › 7.4V system - is it safe?
 Print TOPIC  Make Suggestion 

 7  Topic Subscribe

Tuesday, September 26 - 4:45 am - Copyright © 2000-2017 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online