DS3421 - Alloy or Plastic?
05-23-2004, 04:35 PM
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DS3421 - Alloy or Plastic?
I bought two DS3421's for a JW slope glider. One of the servos failed on the third flight. One or two teeth let go on one of the gears, then the rest soon followed. So I ordered a new gearset for the 3421 at about $30 shipped. I opened the servo to do the swap and found that the entire gearset except for the out-gear assembly is plastic. This is an $85 servo. The description on the Horizon site says:
"A durable composite-metal geartrain composed of hard-anodized aluminum and hardened steel and brass gears provides backlash- free operation."
This "composite-metal" gearset is the only available replacement gearset listed on Horizon's site for this servo.
http://horizon.hobbyshopnow.com/prod...prod=JRPSG3421
I have not pulled out the other servo to check this as it's a bit of a PITA to remove.
Now my main problem is getting the broken gears out of the servo for replacement. It seems there is (was) a micro set screw inside the out-gear assembly. Is this correct? The reason I said "was" in the previous sentence is because when I went to turn the screw it pretty much disintegrated leaving a small pile of metalic shavings when I turned the servo upside down. I went and bought a Craftsman 5/64" flathead screwdriver to get at the screw, my smallest jeweler's screwdrive would not fit into the assembly at all. There was a lot of slop as the end of the blade was quite slim and I shouldn't have forced it, but I was trying to get out to fly.
Any help would be greatly appreciated.
"A durable composite-metal geartrain composed of hard-anodized aluminum and hardened steel and brass gears provides backlash- free operation."
This "composite-metal" gearset is the only available replacement gearset listed on Horizon's site for this servo.
http://horizon.hobbyshopnow.com/prod...prod=JRPSG3421
I have not pulled out the other servo to check this as it's a bit of a PITA to remove.
Now my main problem is getting the broken gears out of the servo for replacement. It seems there is (was) a micro set screw inside the out-gear assembly. Is this correct? The reason I said "was" in the previous sentence is because when I went to turn the screw it pretty much disintegrated leaving a small pile of metalic shavings when I turned the servo upside down. I went and bought a Craftsman 5/64" flathead screwdriver to get at the screw, my smallest jeweler's screwdrive would not fit into the assembly at all. There was a lot of slop as the end of the blade was quite slim and I shouldn't have forced it, but I was trying to get out to fly.
Any help would be greatly appreciated.
05-23-2004, 05:57 PM
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RE: DS3421 - Alloy or Plastic?
Well, ignore my first paragraphs above. I realize now that I bought a "standard" nylon-gear version of the 3421. The horizon site leaves a bit to be desired... If you use the search function at this page:
http://horizon.hobbyshopnow.com/
... and you search for "3421" you will find the 3421-SA standard servo for $79.99 along with the replacement case and the replacement alloy gearset. There is NO DESCRIPTION at all for the servo at the listing. You cannot find the 3421-Metal version using the search unless you know the full part number: JRPSDS3421. The metal version is $84.99. If you click the JR logo on the same page and then use the drop-down to list servos, YOU CAN ONLY FIND THE METAL VERSION, the "SA" version doesn't exist.
I had originally searched for "3421" and purchased the "SA" version thinking they were metal due to fact that the only replacement gearset that is retrieved for that search is metal and also due to the fact that there is no description for the servo. I discovered the metal version later but I thought it was the same servo, with a $5 price increase.
Danny, sorry for the rant. If you could please help me with the question of removing the gearset on the broken servo, I would appreciate it. I'd really prefer not to have to send it in.
Live and learn I guess.
http://horizon.hobbyshopnow.com/
... and you search for "3421" you will find the 3421-SA standard servo for $79.99 along with the replacement case and the replacement alloy gearset. There is NO DESCRIPTION at all for the servo at the listing. You cannot find the 3421-Metal version using the search unless you know the full part number: JRPSDS3421. The metal version is $84.99. If you click the JR logo on the same page and then use the drop-down to list servos, YOU CAN ONLY FIND THE METAL VERSION, the "SA" version doesn't exist.
I had originally searched for "3421" and purchased the "SA" version thinking they were metal due to fact that the only replacement gearset that is retrieved for that search is metal and also due to the fact that there is no description for the servo. I discovered the metal version later but I thought it was the same servo, with a $5 price increase.
Danny, sorry for the rant. If you could please help me with the question of removing the gearset on the broken servo, I would appreciate it. I'd really prefer not to have to send it in.
Live and learn I guess.
05-24-2004, 10:17 AM
#3
RE: DS3421 - Alloy or Plastic?
I'm sorry for the confusion on the 3421 servo. Down inside the output gear you can get to the end of the pot shaft, its not a set screw so it sounds to me like the pot is damaged. You will need to send it in. The 3421 doesnt have a set screw anywhere. The output gear is a press fit but it pulls off with a little effort.
