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Old 11-21-2010, 11:28 PM   #16
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Originally Posted by steve307b View Post
To me it looks like your carb needs twisted to straiten up that angle on your throttle linkage. I have to have my throttle arm at almost a perfect 90 deg off the servo horn, as most guys do. That angle just looks wrong. But hey if it works , great. So you dremeled off the tabs on the servo tray to except the tray stiffner? And did the holes line up?
yep been working fine for 6 months, i cant twist the ball end around the grub screw is WAY to tight, even at 200c
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Old 11-22-2010, 12:16 AM   #17
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Rather than using a brace (which is the equivalent of shimming your servo up) why don't you actually just shim the servo up 1-2mm you will get the same exact result without modding a brace to make it fit. I would suggest that you find and use longer screws cause they tend to strip out when you use the shims...

I am sure chassis flex does actually twist the radio tray but I really doubt that its enough to cause the servos to fail. There are a bunch of guys at my track that literally cut their Losi radio trays in half which make it next to impossible for chassis flex to cause the servo to twist. They still kill servos left and right.

I'm trying to share what the problem is and no one seems to get it so lets try to dumb it down.

If your chassis touches your throttle servo its going to cause it to fail...

So do whatever you can to keep your servo from touching your chassis

Shim it up
Trim up the Side Guard (do this anyway)
Make sure your EPA's don't make your servo flex into your chassis (or close to it)
Make sure your throttle linkage isn't twisting your servo into your chassis (or close to it)

This isn't rocket science... But figure if your radio tray flexes 1mm on the table its actually flexing 2-3mm on the track as the chassis moves around.

That said things that I have tried that didn't work for me:
-Modify the Radio tray servo wires don't rub. A good idea but not a fix for servos dieing because they hit the chassis

-Cutting the radio tray into two pieces. Doesn't prevent the servo from hitting the chassis or side guard.

-O-Rings under the rear of the radio tray (under the battery) with a longer screw. This fix was for the 1.0 8ights, the radio trays in the 2.0 are already taller to compensate for this DON'T DO IT ON A 2.0!

-The shotgun: Do every mod you can find on the internet... I can promise you beyond any doubt that the only mod you need to do at all is trimming the side guard and using shims if your servo is close to the chassis... Thats it... Nothing else needed...

On a side note Losi saw this problem on the 1.0 8ights and the fix was to raise the back of the radio tray (under the battery) with a couple O Rings and using a longer screw "to help reduce the effects of chassis flex". Think about that for a second... This doesnt prevent the radio tray from twisting or flexing ... Instead it raises the throttle servo an extra 1-2mm of the chassis preventing it from hitting and causing the servo to fail...
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Old 11-22-2010, 12:32 AM   #18
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Originally Posted by 808gx7r View Post
this is not being biast or anything.

best thing to do with a losi radio tray is to put in a Savox SC-1258TG servo.
digital 12kg, AND its not as tall as the other standerd size servos, your left with about 3mm from the chassis and guard.

i tryed that and so far good luck after like 8 months... have recently put in a KHDZ radio tray stiffner to remove the radio tray flex.(hasnt effect performance at all)

and my alpha cant have its carb ball turned around so my throttle rod linkage is on a 45DEG angle mybe more. no problems at all.

Here is a perfect example of what I am saying. Savox servos are smaller than the hitec JR KoPropo and Airtronics servos and literally have no chance of touching your chassis so they should last for a really long time as long as your EPA's are correct.

Now if they were only rated at 7.4v and a little faster
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Old 11-22-2010, 12:53 AM   #19
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Originally Posted by ghost68 View Post
Here is a perfect example of what I am saying. Savox servos are smaller than the hitec JR KoPropo and Airtronics servos and literally have no chance of touching your chassis so they should last for a really long time as long as your EPA's are correct.

Now if they were only rated at 7.4v and a little faster
I just bought these savox servos and they're HV (7.4)

1267mg
* Torque: @7.4v - 291 oz-in / 21 kg-cm
* Speed: @7.4v - 0.09sec/60°
* Voltage Range: 4.5v-7.4v
* Weight: 62g
* Motor: Coreless
* Gear: Steel
* Case: Aluminum Heatsink
* Output Shaft: 25T Spline (Futaba)
* Case Size (LxWxH): 40.3x20.2x37.2mm

1268mg
* Torque: @6.0v - 208 oz-in. (13 kg-cm) / @7.4v - 361oz-in. (26 kg-cm)
* Speed: @6.0v - 0.13sec/60° / @7.4v - 0.11sec/60°
* Voltage Range: 4.5v-7.4v
* Weight: 62g
* Motor: Coreless
* Gear: Steel
* Case: Aluminum Heatsink
* Output Shaft: 25T Spline (Futaba)
* Dimensions (LxWxH): 40.3x20.2x37.2mm

I really happy with them Can't you tell
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Old 11-22-2010, 01:05 AM   #20
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Originally Posted by Sein View Post
I just bought these savox servos and they're HV (7.4)

1267mg
* Torque: @7.4v - 291 oz-in / 21 kg-cm
* Speed: @7.4v - 0.09sec/60°
* Voltage Range: 4.5v-7.4v
* Weight: 62g
* Motor: Coreless
* Gear: Steel
* Case: Aluminum Heatsink
* Output Shaft: 25T Spline (Futaba)
* Case Size (LxWxH): 40.3x20.2x37.2mm

1268mg
* Torque: @6.0v - 208 oz-in. (13 kg-cm) / @7.4v - 361oz-in. (26 kg-cm)
* Speed: @6.0v - 0.13sec/60° / @7.4v - 0.11sec/60°
* Voltage Range: 4.5v-7.4v
* Weight: 62g
* Motor: Coreless
* Gear: Steel
* Case: Aluminum Heatsink
* Output Shaft: 25T Spline (Futaba)
* Dimensions (LxWxH): 40.3x20.2x37.2mm

I really happy with them Can't you tell
Hehe guess what just got added to my Christmas list
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Old 11-22-2010, 01:12 AM   #21
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Originally Posted by ghost68 View Post
Here is a perfect example of what I am saying. Savox servos are smaller than the hitec JR KoPropo and Airtronics servos and literally have no chance of touching your chassis so they should last for a really long time as long as your EPA's are correct.

Now if they were only rated at 7.4v and a little faster
their new HV ones are rated at 7.4V and i think they are even smaller by about .2mm, the HV ones kick some serious butt.

as for savox's, i've run them for 2 years never had one fail on me
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Old 11-22-2010, 04:01 AM   #22
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Thank you everybody for the insight on this issue. I looked at side guard issue and found that the servo was rubbing on the guard when it was just sitting on the bench. the epas' are set correctly, that I am sure of. I also noticed that the servo was 1mm off that chassis. It looks like my issue may be the guard and chassis. As soon as my servo comes back, I will addresss the two issues. Thanks again.
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Old 11-22-2010, 10:38 AM   #23
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Originally Posted by ghost68 View Post
Rather than using a brace (which is the equivalent of shimming your servo up) Nope. Raising the servo gets it off the frame, but that doesn't keep the servo pod from flexing diagonally. Effectively making the servo case top a stressed-member..



If your chassis touches your throttle servo its going to cause it to fail... Yes; however I shimmed mine WAY up with the blocks and it wasn't touching to begin with. Still had failures.

So do whatever you can to keep your servo from touching your chassis

Shim it up
Trim up the Side Guard (do this anyway)
Make sure your EPA's don't make your servo flex into your chassis (or close to it)
Make sure your throttle linkage isn't twisting your servo into your chassis (or close to it)

Did *all* that to begin with before ever running the car.

This isn't rocket science... But figure if your radio tray flexes 1mm on the table its actually flexing 2-3mm on the track as the chassis moves around.
Quoted text has been edited for length and relevant content.

Having been in the hobby many years, I've run various platforms and seen a lot of issues.

Yes, the servo smacking the frame will kill it. However, we used to mount servos DIRECTLY to the frame plate and we didn't have these issues. Granted, that's not quite the same as the servo getting 'impacted' by the frame.

My 2.0 had the servo raised, sideguard trimmed, EPA's set, etc. etc. etc. Textbook setup giving it every chance to live. Ran on NiMh and regulated Lipo; lost them on both setups.

Finally gave up and made my braces and lowered the servo down 1mm (had raised it 2mm). Zero failures now; whereas before I was losing a Hitec premium 7-series digital every 4 hours of runtime (or less).

And no, I don't hit the wall or nose-dive off every jump. I'm pretty easy on the car and don't break or dnf...matter of fact, the most I've ever DNF'd was when these servos were dying.

Just FWIW the servo shouldn't be a stressed member of the tray. To me, the tray needs at least 1-more mounting post between the battery box pod and the servo.
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Old 11-22-2010, 01:48 PM   #24
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Agree 100%. I don't care who says what, there is a problem with the design of the tray. Has to be. Way to many failures floating around. I have never been anal about setting up a servo in any other car but I have to be with the Losi. Sometimes I hit it lucky and other times I dont.
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Old 11-22-2010, 02:19 PM   #25
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made my braces >>>> mblgjr

Would it be possible to see a picture of the brace
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Old 11-22-2010, 02:21 PM   #26
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ugh

I'm not saying that the radio tray isn't flawed but where its flawed is where everyone seems to have trouble

1.) It's too short and the servos are too close to the chassis
2.) It's too close to the side guard which is what is really killing these servos

The theory that the radio tray twists the servo and causes the gears to bind up and then burning up the motor is flawed... Servo cases are way too strong for that... What is really happening is the whole servo is twisting and hitting the side guard or chassis....

Ask Hitec how all of these servos fail... Broken motor tabs... Where are the motor tabs you may ask? At the bottom of the servo where it hits the chassis...

Why do so many Losi 8ights kill so many servos? It is hands down the most popular model of noob race car out there period. For someone new to the hobby its kinda hard to turn down a RTR kit that comes with everything but fuel and is competitive out of the box... Why do the RTR Servos last so long? because they are too small to hit the chassis. On the other hand they burn up because they aren't strong enough for the job...

What happens is someone buys a rtr then sees that racer-x has upgraded their servos and now has to keep up with racer-x. They have no idea what an epa is or the importance of your linkage running at 90 degrees... They don't know that if you put a hitec servo in the losi radio tray its going to be rubbing on the side guard and throw off your carb linkage compounding the problem. They don't understand chassis flex and why servos die. What they do know how to do is complain about a problem they don't understand. So of course losi servos are going left and right... It is a great starter platform and new people just don't know.

On the other hand we have die hard racers that burn through servos as well...
Ill tend to blame complacency here and if you really did make sure that nothing is touching your throttle servo then maybe the servo failed because it was going to fail anyways regardless of how it was used...

All that said I have 5 gallons on my throttle servo now on a pretty brutal track I don't use a tray stiffener and never will.
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Old 11-22-2010, 02:37 PM   #27
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Well put.
I set mine up and trimmed the guard and use heat tape on the chassis (under the servo) just for heat protection. No trouble yet but I've had trouble before.
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Old 11-22-2010, 06:46 PM   #28
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Quote:
Originally Posted by 808gx7r View Post
this is not being biast or anything.

best thing to do with a losi radio tray is to put in a Savox SC-1258TG servo.
digital 12kg, AND its not as tall as the other standerd size servos, your left with about 3mm from the chassis and guard.

i tryed that and so far good luck after like 8 months... have recently put in a KHDZ radio tray stiffner to remove the radio tray flex.(hasnt effect performance at all)

and my alpha cant have its carb ball turned around so my throttle rod linkage is on a 45DEG angle mybe more. no problems at all.
Why cant you you turn the carb ball around on your alpha, alls you have to do is loosen the set screw and spin it around.
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Old 11-22-2010, 07:10 PM   #29
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Why cant you you turn the carb ball around on your alpha, alls you have to do is loosen the set screw and spin it around.
I think he said he couldnt get the set screw loose. There's gotta be away to get it out though Little easy out bit maybe
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Old 11-22-2010, 09:01 PM   #30
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To understand how to prevent servo failure you have to understand why they fail

Losi has chosen to have a radio tray instead of a radio plate like a lot of other manufacturers. This makes life easier when maintaining your kit but it causes all kinds of problems because of how flexible the plastic is. This tray flexes like crazy when you’re out on the track and if your EPA’s and linkages aren’t just right the radio tray flexes even more. When the tray flexes it literally twists the gears inside the servo causing them to bind up and then either strip or fry the motor driving them. In addition to radio tray flex causing servos to bind up inside the servos it also causes the servos to flex from side to side and can cause the servos to hit the side guards on the chassis or even worse the chassis itself. If your servo suddenly hits the chassis or side guard it can put an extreme load on already bound up gears and now you are really asking for trouble.

Servos only have to be made to a specific length and width for the mounting holes. Contrary to what you may believe the shims that you have to use with different brands of servos are not to keep the servo in line with your carb and brakes but instead to keep the servo from bottoming out on the chassis. This is why "cheap" servos seem to last longer they are generally shallower because they lack the digital circuitry. A shallow servo doesn’t bottom out and isn’t really affected by chassis flex so they seem to last longer.
To add to this problem there are two available chassis options for the 8IGHT and 8IGHT-T. The RTR chassis and then there is the "Flex Tuned Chassis" the difference between the two is that the Flex tuned chassis has cutouts to give the servos more vertical clearance and that helps keep the servos from bottoming out during chassis flex. Yes you are more likely to burn up more servos if you don’t upgrade to the better chassis.

There are so many theories/fixes at my track and everyone has problems. I believe that there are a few major variables here that cause these servos to fail. Any of the items listed below can cause a servo to fail by itself and the effect is only compounded when there more than one thing is wrong.

1.) EPA's… If your servos are pulling so hard that your radio tray flexes you are doing it wrong. Losi has a very specific guide for this on their website and I have summarized it a few posts above this one. If you are causing your radio tray to flex on the bench then it is only amplified out on the track with chassis flex. Everyone says their epa’s are correct and they still fry servos… Keep Reading…

2.) Improper Carb Alignment... This one is probably the most overlooked that I see, if the throttle linkage isn't perfectly parallel to the chassis it will cause the gears inside the servo to bind up. Add this to the chassis flex from hitting those jumps at full throttle and then boom your servo fries because it bottoms out or hits the side guard.

3.) Not enough clearance around the servos… This is the one that no one seems to know about. While it is really easy to make sure that your EPA’s and linkages are perfect you probably wouldn’t think to see if your servo is touching anything… Chances are that if you have replaced your stock servos with something more expensive your servo is already touching the side guard or the chassis. This is especially the case if you are on your second or third high end servo in less than a gallon or two of fuel. Chassis flex will cause your servo to fail extremely fast if the servo is in direct contact with the chassis or side guard. Servos are not designed to handle the extreme vibration and shock that your chassis goes through. I had several 7955tgs burn up within 15 minutes of being on the track because they were touching the side guard. Fortunately there is a pretty easy fix for this; use shims to keep the servo from touching the chassis and if the servo is touching the side guard you just cut away where it touches the servo and problem solved.

4.) All electronics can die for no reason at any time… Yea blame god for this one even with everything perfect a servo can just die for no reason... Not a lot you can do about this one…

If you don’t check all of the above every time you change a servo then you can expect to spend a lot of time mailing your servos in for service.
Nice post with good info!
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