Help guys I was getting ready to install a bunch of decoders in several GP35's and then I ran into a snag with one of them. My usually method is to run the engine around a test track for about 1/2 hour varying the voltage and direction to seat the mechanism. One unit it is noisy, a miniature coffee grinder and I cannot get it to settle down. Most of my units at 6 VDC pull about 50 ma. This noisy one pulls 100~110 ma at 6 VDC. Some thing is binding and I can't seem to figure it out. I have disassembled the unit and the motor spins freely the gears appear to be ok. I have not been able to determine the source of binding. Any suggestions out there where to look or is this a defective unit from Micro-Trains. The unit has only been out of the box for 20 minutes.
I don't have a GP35, but did you check that the trucks roll freely when they are removed from the chassis? If you say the motor alone is running fine, then the trucks are probably the problem.
If you'd like, send it back to me at Micro-Trains and I'll replace the chassis with one that cooks along instead of Coffee Grinding! Cheers Joe MTL
I find most of the problem is due to improperly instal worm gear bushings. They are extremely hard to align properly. you have to make sure the fit into the slots. Even when you have them in the proper position, they tend to move when your installing the trucks and screws. After I tighten the screws all the way, then I loosen the screws a quarter turn. The second place I would check is the truck. The truck should be free rolling. I have heard cases of plastic jamming the gears in the truck, specialy on the batch of GP35 where they used heat to weld the sill to the frame. On your decoder installation, do you have the new 123 with the smds? If you have the old style with the big led, let me know I have a easy fix to the oversize leds.
David, intal the decocer upside down like this. Note the retaining post is broken off. This is very important part of installing it upside down. I shorted a decoder because of this post. Then you are going to correct the lights and directions through cvs. Set cv 29 to 7 to correct the direction, and change cv 33 to 1 and cv 34 to 2 to correct the direction of the lights. Its lot easier then try to file down the light and cut the cab interior to accomodate the led.
I have had this problem after installing a decoder too. What I did to fix it was loosen all 3 frame screws 1/4 turn, and gently pry the frame halves apart at the front, rear, top on both sides of the decoder, and reinstall in the shell using only a pushing the shell down movement without and squeezing of the sides inwards. After that, everything is loosened up an trucks rotate freely, and your current draw should go down to 35ma at 8 volts. If not, something more serious is happening.
Your best bet is to send it back as Joe suggests, but if you are adventurous and want to dig into it yourself... Good advice from shamoo737 and pray59 on the worm bushings. They are hard to align, as you rotate each bushing you should feel a snap as the tab drops into the slot in the right side chassis casting. There are no corresponding slots in the left chassis casting, so when assembling keep the right chassis down to prevent the bushings from falling out. Sight along the worms and motor from the side, if the bushings are seated properly the worms shoul lie perfectly flat and straight. It tipped upwards a tab is not seated in it's slot. The worm shaft bushings are NOT symmetrical, and their orientation is critical, they have a definite front and rear. If installed backwards the loco will run slow and pull more current due to biding of the worm. Look closely at a bushing, the tab is flush with the bushing surface at one end with the indents in the bushing flat, but is inset very slightly (abt 0.2mm) at the other end. The inset ends must be positioned towards the worm. If not, the loco will run very slowly unless the chassis screws are loosened and the chassis halves separated slightly. When the bushings are oriented properly the chassis can be screwed tight and the GP35 will run at normal speed without causing binding of the bushings to the worm. Also note there are thin flat shim washers at each end of the worm, not shown on the assembly drawing that comes with the GP35. These tend to stick to the bushings, so if you have to turn one around move the shim washer back towards the worm. If you ever have to take the trucks apart for cleaning, the 3 inside gears are not identical but are not named separately on the assembly drawing. They will fit the wrong way but will not run properly. The top gear that meshes with the worm is slightly larger than the other two and has 13 teeth. The lower two gears that mesh with the wheel axle gears are smaller and have 12 teeth. Make sure the wheelwipers are slightly touching both wheels at the same time without excessive pressure, and that the top of the wiper contacts the chassis.
I have also some problems with my GP-25 running. It is now running slow and stalls easily. I can se that one truck is bending upwards making one wheel set hang almost in the air. So I think maybe that have got the bushings installed the wrong way or perhaps mixed up the gears in the truck. I have to take it apart again and test some more. It used to run just great
Torsja, it happen to me also, but on a AZL. Somehow a piece of smooth it got into the gears. When the gears are jam, the front wheels lift off. I took the offending material out, and its running smoothly again.
Yo Glen !!! Thanks A WHOLE LOT !!! I'm at Torsja's with Henrik and the Zmod group. I just took Torsja's GP apart and placed all the parts, as I do, 1 for 1 on the white cloth. I cleaned, dried and lubed each part with a quite light viscous oil. Trucks run free. Assembled (I hate those rediculous 1980 F7 tabs) and it runs the same, about half speed, just like it did before I started. So now we have the possible secrets. But I am leaving. Torsja will check the two worm gear shafts to see if they are different (I know the fly wheels are) and, if there really are 13 and 12 tooth gears (I'm not biting on that one but respect all your experience and I am sure Joe D would drop right in and correct it like a type if it were not true). Torsja can report later. Or, if I get up early enough in the morning before seeing Hans Riddervold of AZL . . .
The shaft bushings can be a real pain in the assembly process. To help seat the bushings closest to the motor, slide them AWAY from the motor first. Then the tabs should fall into their slots with minimum effort. When re-assembling the locomotive the shaft bushings are very easily knocked out of position. Keep the right chassis down at all times while GENTLY adding the left chassis and trucks. Prior to chassis screws run the loco to test. Or if you have calipers measure 0.65mm between the chassis halves. If the measure is 0.7mm or greater a bushing tab has fallen out of the slot and the re-assembly must be repeated.
i wonder if the old N scale fix would help here. that was to remove the INNER bearing block or blocks (leave the blocks on the extreme ends). i did this when i shortened a GP9 mechanism to make my CF7. works just as well, smooth and quiet as one shaft end is supported by the end bearing block and the inner shaft end is supported by the universal joint. it would tell us something if this was tried. i'm also wondering if the "T" head on the shaft end (which fits in the universal joint) could be too long or too short. too long and it will really bind. to short and it will rattle and run eratically. just thinking out loud. dave f.
David, I did couple of rebuilds, and on some of them, the shaft is not completely straight. Even when you align the notches correctly, when you mate the two half together it will go out of alignment. The uneven pressure pops them out. The ones with straight shafts are a breeze. I look under the truck opennings to make sure the tab goes into the slots. If they are not, then I use a small screw driver to push them into the slot.
Haven't tried this but could result in worm to truck mesh skip as the universal joint to the flywheel has got some freeplay and the worm could bounce around at that end. This could damage the 13 toothed gear. Also without the motor end bushing the worm back and forth travel is limited only by the universal joint so another reason the worm may not properly engage the truck gear. If it was my loco I'd try it, but the one I have opened up belongs to someone else.
If the shafts cannot be made to sit straight check that one or more bushings are not oriented back-to-front. The end of each shaft bushing with the small inset in the tab must face it's worm, see my previous post yesterday. If not the tabs will appear to go into their slots but one end of the tab will tilt upwards (and make the shaft appear non-straight), forcing the chassis together will squeeze and damage the tab making it necessary to trim with a sharp knfe it you want it to fit into the slot again. The GP35 is a gem of precision machinery, the tabs are the way they are so that the worm back and forth freeplay is almost non-existant.
Randy, I spent all day today cleaning up the GP35 repair and assembly procedure and placed it into the yahoo list enZyclopedia under "Performance Zone / Locomotives". I tried to include a couple of photos but they did not work in HTML. I could post as a Word .doc, but that eats up a lot of storage space and anyway don't have many photos yet. As per your suggestion I am going to take photographs as I re-assemble the last of a batch of GP35s in for repair, then post the photos here and in a folder on the yahoo list. My photographic equipment and skill are not great but will do whatever possible. If anyone is interested in the entire lengthy procedure I could post it here too.
Glen, if there is one thing you dont do to the shaft is to bend it. Its made of a ceramic material. It will break when you bend it, and yes, I did check that the tabs were facing the right position. Your information about the direction of the tabs was very useful, but the bend was from the shaft and not from the bushings.
I for one would be very happy to see Glen's repair and assembly procedure posted here. It would be extra cool if the pictures were also posted, so everyone can benefit, as pictures are worth a thousand words too!
