Question about Hi-Tec Servos

[zeek_RC]

Do Hitec servos, such as the HS-645mg have fuses built into them? we have burned up several of these servos before, that were being used for throttle control. A friend of mine stated that they have a small fuse built right onto the circuit board but I have no idea how accurate this is. If they do have a fuse built in, do you think it would be possible to fix it?

Also, who else makes steel gear servos with at least 133 oz in of torque that are less expensive than Hitec?

thanks,
zach

[rccardude04]

I've never seen a fuse. Typically servos are engineered so that they won't blow themselves up unless you stall them really badly (wrong endpoint settings), and then they really fry themselves nicely.

If they're burning up, what makes you think a cheaper servo will be better?

-Eric

[zeek_RC]

I had never seen one either but my friend said they were built into the board and were pretty small but I had no idea. What do you mean by wrong end point settings? Like being thrown to far to one side?

I'm more interested in less-expensive and not cheaper quality, but with the same specs as Hi-tec. I'd like to find a less-expensive one because we have burned up several of them already and the budget is tight.

[drummin89]

A new servo isn't going to be the solution because you will continue to burn them up. You need to find out why they are burning up.

On my ofna the steering servo would continue moving even though the wheels couldn't turn any more. If I continued to hold the servo further than it needed to go it would eventually burn up. This is where a radio with endpoint adjustments comes in so you can dial back how far the servo moves before stopping. On my ofna I have the servo setup so it only moves70% in either direction before stopping. Basically set the endpoints all the way in (like 50% or whatever the minimum) and put the wheels off the ground and turn the wheel in both directions and increase the endpoint until you no longer see the wheels turning. Its the same with throttle servos and servos for aircraft.

A cheap fix incase your radio doesn't have endpoint adjustments would be to play with diffent length servo horns or different mounting positions on the servo horn. The further out you have the linkage mounted from the center of the servo horn, the further the linkage will move. Move it closer to the center will decrease the distance the linkage moves.

Also are your servos coming in contact with water?

[rccardude04]

Less expensive servos will be worse in terms of blowing up. Drummin nailed exactly what I meant by the endpoints. Sorry I didn't explain that more earlier.

A good throttle servo I've found is the JR Z4800T. It's an 85 dollar servo but they don't blow up very darn often.

Another thing you may try is to send the 645MGs that you've blown up into hitec for service. They are pretty lenient on warranty claims a lot of times. :)

-Eric

[zeek_RC]

Thanks guys for your help.

I should probably clarify what the servos are being used for. These servos are for throttle control on Briggs and Stratton Vtwin 16Hp motors. These motors are being used for a University Club to build a 1/4 scale tractor for tractor pulls.

My guess is the servo are being held to far, for to long. I'll have to look into it to see what can be done to fix it. Thanks again guys.

zach

[drummin89]

I would also check to make sure the throttle linkage/cable for the carb moves freely and without resistance as to not put strain on the servo. I would think a throttle body on a carb would be easy for a single standard size servo to move but if not you could always rig it up to use 2 servos or look into getting a 1/4 scale servo. rc4wd has one listed for $50. http://www.rc4wdstore.com/2/product_info.php?cPath=17&products_id=819

[zeek_RC]

does anyone make a servo that is more than 6.0V?

[drummin89]

You can try this place http://www.robotmarketplace.com/products/rc_servos_main.html

they might have something above 6v. What seems to be the problem? Receiver not supplying enough power to the servo? If so you can always wire the battery directly to the receiver. There should be a diagram on the internet somewhere on how to do it.

[FESTER2004]

i would look into the bigger scale rc planes maybe?????

[rccardude04]

does anyone make a servo that is more than 6.0V?


For the hobby (R/C) market, almost all of the servos are rated between 5 and 6 volts. Some don't even work on 6 volts.

There are a few really high end servos that are good to 8 volts for a direct 2s lipo connection, but those are still the $200 servos for the most part.

Maybe the industrial market has something for the 12v range, but to stick with hobby stuff, you're pretty much stuck with 6-8v.

-Eric