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Old Dec 03, 2011, 08:39 PM
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Originally Posted by vienquach View Post
Cory, you are absolutely right (best performance/price), but that didn't answer my question.



Yeah, I think so too since 7955 on 2s is like 400+ oz.in vs 7985 on 6.0 is about 170+oz.in of torque.

If the 1258TG servos work better than 7985s, I could save "half" the price choosing it over 7955 TG. Align DS610 is similar to 1258 TG (same spec) and is sold on ebay for $50/each where as the 7955 TG is about $90/each.

Anyway, was just curious in performance difference, not about price since I have both.

Vien
Ok so for the cost 7955's are the performance winners but what about your throttle servo do you really need a work horse to drive the throttle? Should you purchase a match set or do you opt for a lesser model? Is my thought process wrong on this or would this not be smarter?

What servos are others using on this planes throttle?
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Old Dec 03, 2011, 08:43 PM
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I would think that would make you a little bit of a baddie.

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Originally Posted by jhorton View Post
Ok so for the cost 7955's are the performance winners but what about your throttle servo? should you purchase a match set or do you not need as much of a power house to run the servo? Im guessing get a digital servo that is fast but not as strong and can run off the 2S like the 7955's can if that is your cup of tea. Please correct me if I am wrong.

What servo are others that have build this plane running?

Also on a side note while I have been waiting for my 74 to get to 3dhs I think I changed my mind and like the silver better than the red now. would it make me a bad person to call and change my mind
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Old Dec 03, 2011, 09:02 PM
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Originally Posted by jhorton View Post
Ok so for the cost 7955's are the performance winners but what about your throttle servo do you really need a work horse to drive the throttle? Should you purchase a match set or do you opt for a lesser model? Is my thought process wrong on this or would this not be smarter?

What servos are others using on this planes throttle?
I use 7955 on my 89" Slick. I'm using a cheaper Hitec 5665MH HV servo for the throttle. It's designed for 2s lipo, so all of my servos are running high voltage. No need for any type of regulator, which eliminates a failure point.

A fast throttle servo is well worth the investment. It makes a big difference in throttle response.

I'll be running electric on the 74", but it'll get 7955, too. You probably don't need a full size servo on the throttle of a 30cc plane. A nice quality high voltage servo with some decent speed would complement your plane very well if you plan to run 7955 servos.

http://www3.towerhobbies.com/cgi-bin...?&I=LXZTZ1&P=7
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Old Dec 03, 2011, 10:18 PM
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Fast throttle servo is critical....I've used 7940's on my 103 and 104. I am using a 7955 on my 74 so all servos are the same and I'm standardizing on 7955's so they'll also serve as spares for my bigger planes or I can strip the 74 and drop that equipment into a 50cc sometime if a 50cc edge is ever produced....or a 10x" edge......
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Old Dec 04, 2011, 12:47 AM
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Originally Posted by Bivens View Post
Fast throttle servo is critical....I've used 7940's on my 103 and 104. I am using a 7955 on my 74 so all servos are the same and I'm standardizing on 7955's so they'll also serve as spares for my bigger planes or I can strip the 74 and drop that equipment into a 50cc sometime if a 50cc edge is ever produced....or a 10x" edge......
I feel a more precise servo is more important then fast!

If you have one that is too fast you will be moving the throttle opening on the carb faster then it can react! But this is just my theory. I have not tested it!
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Old Dec 04, 2011, 12:52 AM
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Great input thank you both.
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Old Dec 04, 2011, 02:23 AM
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Originally Posted by Bivens View Post
Fast throttle servo is critical....I've used 7940's on my 103 and 104. I am using a 7955 on my 74 so all servos are the same and I'm standardizing on 7955's so they'll also serve as spares for my bigger planes or I can strip the 74 and drop that equipment into a 50cc sometime if a 50cc edge is ever produced....or a 10x" edge......
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I feel a more precise servo is more important then fast!

If you have one that is too fast you will be moving the throttle opening on the carb faster then it can react! But this is just my theory. I have not tested it!
Fast + precise are both important.
Hitec 5665MH is good enough, IMO, but it doesn't hurt to run the 7955/7940 on 2s for throttle if money is not an issue.

Vien
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Old Dec 04, 2011, 10:46 AM
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A gas engine will almost never exceed our expectations on response speed....it will almost always react slower than we like....especially if that pilot also flies small electrics. When you combine that slower response with a slow servo....you really notice it.

Where you notice the precision is on returning to the idle setting. Think of how we use our throttle.....there's very little time where we hold it steady and expect "centering" like on our other controls....except on the low end where you want it to idle slow and if you get too low it'll die.

I'm going for speed on a throttle servo while maintaining precision...that's why I use 7940's on throttle of my big gas planes. I know Wamsy has been glad he also used a 7940 on his 89's throttle.

A gasser with slow throttle servo can never respond faster than that servo...even with the perfect tune and smaller fast-spooling prop.

A gasser with a non-precise servo will have to maintain a faster idle than one with a precise servo.
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Old Dec 04, 2011, 11:09 AM
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Originally Posted by grubby View Post
I feel a more precise servo is more important then fast!

If you have one that is too fast you will be moving the throttle opening on the carb faster then it can react! But this is just my theory. I have not tested it!
True. Don't need blazing fast. .15 is fast enough.


Cory
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Old Dec 04, 2011, 11:13 AM
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Maybe I'm just crazy on my throttle...but I expect it to react VERY quickly. I'm always going to go fast on my throttle. I've got one DLE111 without the fast servo...it feels like driving a diesel engine with turbo lag (compared to the faster servo on my other 3 gassers).
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Old Dec 04, 2011, 11:21 AM
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Originally Posted by Bivens View Post
Maybe I'm just crazy on my throttle...but I expect it to react VERY quickly. I'm always going to go fast on my throttle. I've got one DLE111 without the fast servo...it feels like driving a diesel engine with turbo lag (compared to the faster servo on my other 3 gassers).
I use the Hitec 5625MG on all my 50cc and above planes. They've always seemed fine. I have a HS225MG on my 72'' 330 for the throttle and it's perfect. I've flown a few planes using straight lipo, and the throttle servo being around .10. I thought it was too fast causing a delay between the engine response and servo. Especially when pumping the throttle in a roller.


Cory
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Old Dec 04, 2011, 11:25 AM
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I thought it was too fast causing a delay between the engine response and servo
I see. But if the engine ran better...you'd be able to capitolize on faster servo speed. This is not only a function of servo...but the ability to get a great tune on the engine and combine that with an exhaust that works well. Normally it's felt as the engine not feeling smooth on quick throttle transition. It's like saying......I can't run as fast as I used to, so I'd better not try...when the solution is to put some hard effort into getting into shape......

In this case, sometimes it's very difficult to get small engines tuned perfectly...but when you get there, you know it and then you can take advantage of a QUICK throttle servo.
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Old Dec 04, 2011, 11:30 AM
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Originally Posted by Bivens View Post
I see. But if the engine ran better...you'd be able to capitolize on faster servo speed. This is not only a function of servo...but the ability to get a great tune on the engine and combine that with an exhaust that works well. Normally it's felt as the engine not feeling smooth on quick throttle transition. It's like saying......I can't run as fast as I used to, so I'd better not try...when the solution is to put some hard effort into getting into shape......

In this case, sometimes it's very difficult to get small engines tuned perfectly...but when you get there, you know it and then you can take advantage of a QUICK throttle servo.
True. Some people I know at my fields have stuck a .23 or so servo on a 100cc plane and wonder why the throttle feels weird? You can always dial in expo on the throttle if need be also on some radios. I think anything from .11 to .18 may be the sweet spot. A .06 servo would be way to fast I think.



Cory
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Old Dec 04, 2011, 01:32 PM
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Originally Posted by RC4x4 View Post
I use the Hitec 5625MG on all my 50cc and above planes. They've always seemed fine. I have a HS225MG on my 72'' 330 for the throttle and it's perfect. I've flown a few planes using straight lipo, and the throttle servo being around .10. I thought it was too fast causing a delay between the engine response and servo. Especially when pumping the throttle in a roller.


Cory
5665MH seems to be the HV version of the 5625 MG, so it will work great if you want to eliminate the BEC.

0.10 to 0.15 is fast enough, IMO. Above that is kinda slow.

Vien
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Old Dec 04, 2011, 03:16 PM
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5665-MH Specifications

Motor Type: 3 Pole Ferrite (7.4v Wind)
Bearing Type: Dual Ball Bearing
Speed (6.0V/7.4V): 0.16 / 0.14
Torque kg./cm. (6.0V/7.4V): 8.8 / 10
Size in Millimeters: 41 x 20 x 38
Weight g.: 60g


5495-BH Specifications

Motor Type: 3 Pole Ferrite
Bearing Type: Top Ball Bearing
Speed (6.0V/7.4V): 0.17 / 0.15 Second
Torque kg./cm. (6.0V/7.4V): 6.4 / 7.5.
Size in Millimeters: 40 x 20 x 38 mm
Weight g.: 44.5 g.


7955-TG Specifications

Motor Type: Coreless
Bearing Type: Dual Ball Bearing
Speed (4.8V/6.0V): 0.19 / 0.15
Torque kg./cm. (4.8V/6.0V): 18.0 / 24.0
Size in Millimeters: 39.88 x 19.81 x 36.83
Weight grams: 64.92


I am thinking on going with 4 - 7955's and the 5495 for Throttle.

1. Single ball bearing but with throttle servo there is less resistance should be good.
2. You can still run the 2S batt so you don't have to have a BEC.
3. Less Torque (throttle does not need the Torque)
4. Lighter gears (saves weight).
5. 1/3 cost of the 7955
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