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Old 07-30-2009, 06:40 PM   #1
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Default Losi 8ight 2.0 RTR throttle servo

I'm hoping someone can shed some light on a strangle issue. Here's the long explaination.

Saturday I had my first race day with my new 8 2.0 RTR. We had already purchased a JR 8711 to replace the steering servo but had not yet put it in when the stock throttle servo quit working. After putting in the new steering servo and moving the stock steering servo to the throttle spot, everything was fine for about 15 min and then we lost a second throttle servo. We then put Ina Hitec metal gear servo we had and got through the race day. Tonight, I was prepping the buggy for our race this Saturday and lo and behold the throttle servo quits working. I wasn't even driving it, just going over it and it started responding sporatically then not at all. Every time a new servo went in the end points were set on the radio and there is no apparent binding. I plugged the steering servo into the throttle spot and it responded as expected.

What else could be causing this issue or is it just cheap servos?
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Old 07-30-2009, 07:55 PM   #2
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i had the same issue, it wasnt with a buggy but my sons mt (revo) we didnt have a throttle return spring so there was no tension on the serov and endpoints were set..both the serevos that went out were the servos that came with the losi 2.0 buggy.....lol we changed the servos in the buggy to jr 9100t's an have had no issues yet.....
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Old 07-30-2009, 07:59 PM   #3
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My throttle servo had about 10 minutes of run time before it went. I have done the same thing you did. Put a JR 8711 on steering and moved the steering to throttle. So far it's been ok with about 4 tanks through it.

A friend of mines throttle servo was broken out of the box. So again he put a 8711 in on steering and moved steering to throttle. Then that throttle servo went again. He then put a JR 9100S and it has been fine for many races and run time.

These where both on a 8ight-T 2.0 RTR. Horizon Hobby is taking all the servos back and sending new ones back. The servo's are cheap and most likely would go again but at least there are replacing them.
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Old 07-30-2009, 08:35 PM   #4
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I went through 6 servos this season since I started running the 2.0T in march. I blew up 9100t, 9100s, 7965 each twice. They were all being used on the throttle. You have to make sure nothing is coming close to the servo case. My particular problem turned out to be the side mud guard was hitting the servo case. I trimmed it down and have had no problems since. This chassis has a lot of flex. Check out the mud guard. I bet thats the issue.
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Old 07-30-2009, 08:46 PM   #5
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Thanks for the replies! I have a JR Z8800s coming (hopefully tomorrow) that I hope will hold up for a long, long time! I will check to see if anything is coming into contact with the servo as well. If anyone else wants to chime on on causes, I'd still love to hear them.
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Old 07-30-2009, 09:38 PM   #6
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i have gone threw 4 carbs i think. the way the geometry is on that buggy and my truggy it will mess up your slide. mudbogger knows chris at the chop shop. he tryed 7 times and finally got it right. plus i put a mach .26 carb on it to
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Old 07-31-2009, 03:29 AM   #7
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and i thought it was just mine... i lost the throttle servo after 4 tanks. called horizon, they sent me new one, but i already put a hitec something or other in there and its been fine for the next gallon.

funny story thought, my 2.0 buggy rtr showed up with a left spindle carrier on the right side, so it wouldn't turn. it took almost a month, but horizon finally got me the right parts. good think for locals or i would have had a shelf queen for all that time.
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Old 07-31-2009, 04:27 AM   #8
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I had problems with hitec servos in my 8ight 2.0 race roller for some reason. I think I went through 3 of them on throttle. They were cheaper ones that I had left over from old helicopters but I never had any problem with them doing 3D with a 90 size heli. Endpoints were set right and nothing was hitting. One of them quit working before I even ran the buggy. I almost think it had something to do with the DX3S I am using. The servos would work erratic and not have any strength but when I would plug them into an air receiver they would seem to work fine. I put an old slow Futaba 9202 on it and it has been working fine for months now. I know I need to put something better on it but I hate to since it is working so well now.

I also had the stock throttle servo on my wifes 8ight T rtr die after one lap. I took it apart and it even looked cheap inside.
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Old 07-31-2009, 10:02 AM   #9
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I ran an 8-t last year and the beginning of this year with no throttle servo issues and we all know how many issues others were having with those servos/throttle geometry (I followed that 1.0 adendum to the "T").

Switched to the 8 2.0 and 20 min of run time and the t/b servo just quit with no warning. I had already reviewed the overall linkage setup as it came from factory and noted some very interesting points all should look at:

1. When looking that the actual throttle rod, it was not level with the servo. The carb ball end was rotated down, which made the rod lean down from the servo to the carb. It was quite excessive in my judgement. So leveled that out by rotating the carb ball end up.

2. Then noticed the carb was rotated so that the LSN side was further back and away from the center diff carrier braces (just a point of reference) than my old 8 was. Looking from the top down, this increased the angle at which the carb slid was to the action of the thottle linkage. So I rotated the carb counter clockwise some, being sure not to much that the LSN side would be too close to the center diff mount. While you cannot straighten out the "pull" entirely, it did straight out that angle some.

I made these changes before my servo died. Replacing with an HS-985mg, while replacing the steering w/ with 7955tg. I called Horizon for any more info on the throttle linkage/geometry setup and was basically said there are no instructions, and the servos are junk. I understand that, but I could at least get my old 8-t to run on a JRstock servo for a long time.

Like someone else suggested, I will check the clearances around my new servos once they arrive, to be sure the mudguard doesn't hit, or anything else. Will also check to make sure that the center diff mount hasn't hit the LSN side of the carb under any previous chassis flex.
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Old 07-31-2009, 01:33 PM   #10
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i dont personally run a losi for 1/8, but I have sold alot of them. I have noticed some main things to help increase the life of the servos ( other than the stock 2.0 rtr throttle servo, it is crazy they include a servo with only like 42 oz of torque for throttle, it is the breaking motion that hurts them).

Make sure your linkages are running as straight as possible, any angles in the motion can cause binding and will put a side load on the servo output shaft. Also make sure your carb shaft slides smoothly, no binding. Make sure your end points are set so the servo isnt trying to over extend for break, throttle, and left and right steering. Best way to do this is to pull full throttle, run your end point/travel adjustment up till the throttle stops moving, then back it down a couple clicks. Do the same for brake, and each steering direction, this will greatly greatly increase the life of servos, I have seen it over and over people burning up servos and then watch them throw a servo in, crank the travel up and watch the servos trying to twist out of their cases.

Also make sure nothing is making contact with the case, like the chassis, side guards, etc. Under a hard landing, if the chassis is slapping the servo case, or if the case is sitting aganst the chassis, it will do some damage to the servo, as will the vibration of 1/8 scale. If needed, space the servo up just a bit.

For budget 2.0 RTR guys on a budget or for more of a bashing buggy. Move the stock steering servo to the throttle, and put a JR Z650m on steering, or maybe even a Z4800T. Just make sure to do the above adjustments
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Old 08-01-2009, 04:08 PM   #11
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hello there...

i'll buy a 2.0 rtr buggy, and for now i'm reading all the topic about losi 2.0...

i'm a bit scary about this servos problems....
what about change the st servo for Airtronics 94162Z (144 @ 6.0V / 0.18 @ 6.0V - metal gears) and put the stock st servo on T/b??

in my kyosho DST 1/10 scale i use futaba 3010 and 3004... both are stronger then losi stock servo... don't know why losi put this weaks servos on this great car...
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Old 08-01-2009, 05:42 PM   #12
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Quote:
Originally Posted by su3zero View Post
hello there...

i'll buy a 2.0 rtr buggy, and for now i'm reading all the topic about losi 2.0...

i'm a bit scary about this servos problems....
what about change the st servo for Airtronics 94162Z (144 @ 6.0V / 0.18 @ 6.0V - metal gears) and put the stock st servo on T/b??

in my kyosho DST 1/10 scale i use futaba 3010 and 3004... both are stronger then losi stock servo... don't know why losi put this weaks servos on this great car...
I wouldn't be scared, the RTR is still a great deal. I put an old Futaba 3305 in before the race today and it worked just fine all day. The only way to make this a $700 8ight 2.0 is to use cheap servos. I sent mine back and Horizon said they would be sending better servos back to me.
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Old 09-18-2009, 11:16 PM   #13
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I still run the 8t 1.0 and I've lost 6 throttle servos, three jr650's, a jr590 and 2 jr 9100t's. I have tried orings, backing out the screws in the radio tray 1/8th turn, setting EPA, the addendum, insulating tape, you name it, I've tried it, even tried a longer arm for the carb...still lost one 15 mins. before the A-main last weekend. That was a marathon servo change!!!

The real problem, which losi will not tell you is the radio tray "design". Orings are just a bandaid to extend the life of the servos, without really addressing to real problem. We all agree that it is chassis flex that is killing the servos...think about it though. The steering servo takes alot more abuse than the throttle "should". The steering servo has to constantly be changing directions and holding the front wheels when cornering or landing all crooked. Just think about the amout of abuse it takes. Is it the steering servo that is the problem? No, it's the throttle, why???

Try this...remove the radio tray, and with both hands hold the front and rear of the tray and give it a twist back and forth. While your doing this, watch the amount of twist on the throttle servo case. It is alot. Now try to imagine flying down the straight and jamming the brakes before the corner. When you nail the brakes, start cornering ( chassis starts flexing bad), and then pin the throttle. What do you think is happening to the gears inside the servo? They are in a bind, and when you pin the throttle, you are forcing them to change dirction quickly while they are bound up!

Now look at the way the steering servo is mounted to the tray and how the tray is mounted to the chassis. You'll notice that there is a screw on either corner of the steering servo, (part of the radio tray), effectively mounting the steering servo "directly" to the chassis. Study it and you'll see what I mean. Now what if the throttle servo was also mounted directly to the chassis??? Because the steering servo is mounted in this way, chassis flex does not matter. Right?

So what if you mounted the throttle servo the same way??? But how???

I used a throttle servo mount from my XXX-NT parts box, removed the screws on the back of the throttle servo and let that stupid little thingy that they screw into just get lost somewhere!!! Useless piece of junk anyway. Now I just screwed the screws right into the holes on the XXX piece and now set it aside. I took my dremel and adjusted the chassis so this new addition would fit comfortably to the chassis. I had to cut approximately 3/16 to 1/4 inch off the end of the new "servo mount" so it would fit perfectly when installed to the chassis. Then I measured and marked my holes and drilled two holes to meet the holes of the new servo mount. Finished it off by countersinking the screwholes for a nice clean installation.

Now the servo is mounted solid to the chassis, just like the steering servo. I've been running a jr590 and have had zero problems. I figured I'd run cheaper servos just to prove that it works before running 140 plus dollar servos again.

But remember...you still have set EPA as with any installation.

I refuse to spend the money on a new 2.0 truggy until the problem with the servo is fixed. Our LHS owner has both the 2.0 buggy and truggy and has lost servos on both of them. They are the JR high voltage ones($200 each), so even if Losi says they tweaked the radio tray on the new design, then why are throttle servos still going out???

It seems to me the the losi engineers don't want to admit that they designed a junk radio tray in an otherwise awesome RC car!!!

By the way, for you who wonder if I'm hacking on the losi engineers...well I am a mechanical engineer myself. Just can't imagine why they keep telling us to bandaid it, why didnt they just redesign the tray for the new 2.0???

After looking at other manufacturers designs, losi is dragging their feet.


Quote:
Originally Posted by ShagNastyEk9 View Post
i dont personally run a losi for 1/8, but I have sold alot of them. I have noticed some main things to help increase the life of the servos ( other than the stock 2.0 rtr throttle servo, it is crazy they include a servo with only like 42 oz of torque for throttle, it is the breaking motion that hurts them).

Make sure your linkages are running as straight as possible, any angles in the motion can cause binding and will put a side load on the servo output shaft. Also make sure your carb shaft slides smoothly, no binding. Make sure your end points are set so the servo isnt trying to over extend for break, throttle, and left and right steering. Best way to do this is to pull full throttle, run your end point/travel adjustment up till the throttle stops moving, then back it down a couple clicks. Do the same for brake, and each steering direction, this will greatly greatly increase the life of servos, I have seen it over and over people burning up servos and then watch them throw a servo in, crank the travel up and watch the servos trying to twist out of their cases.

Also make sure nothing is making contact with the case, like the chassis, side guards, etc. Under a hard landing, if the chassis is slapping the servo case, or if the case is sitting aganst the chassis, it will do some damage to the servo, as will the vibration of 1/8 scale. If needed, space the servo up just a bit.

For budget 2.0 RTR guys on a budget or for more of a bashing buggy. Move the stock steering servo to the throttle, and put a JR Z650m on steering, or maybe even a Z4800T. Just make sure to do the above adjustments
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Old 09-18-2009, 11:29 PM   #14
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Set your endpoints right and have make sure the carb pulls out smooth, also leave enough when at WOT you can still pull the carb open a 1.5mm or so past the arm with your fingers. ENDPOINTS !!!!!!
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Old 09-19-2009, 05:30 AM   #15
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so far i havent had any problems thank god
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