Trevor,
You are welcome.
As far as seeing this personally, I have 2 FP7s and 4 Con Cor GPs with this drive. None have failed. I have heard of the motor failing but not the gears/worm.
One thing I noticed, is when new, the gear boxes were fairly tight. After a while, I could hear a momentary squeak from the lead truck when the unit began to move.
After adding some plastic compatible grease (Superlube), to the gearboxes the noise immediately ceased and starting voltage was lowered.
The fact that both of your units failed in the same manner, suggests lubrication was likely the fault. Oil alone is not sufficient, as the boxes are not sealed and oil will eventually migrate out.
Jim
Were the gears kept lubricated? I've found that nylon gears can actually grind each other down if they're running without any good grease or oil.
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Thanks for that Jim - It is definitely a black coloured worm and the motor was as described for the second series of these units. Just interested as to why the front worm on both units stripped about the same time and I wonder if it is/was a common problem with these units?
And again thankyou to everyone who has tried to help!
Cheers from Australia
Trevor
Editor Publisher Railway Modeller Australia
(PM me for the link to the free magazine)
Here is another document showing the internal parts of the truck.
https://download.atlasrr.com/pdf/HO%20FP-7%20TRUCK%20ASS.%20AUSTRIA.pdf
The worm for this second version is smaller and should be colored black. It does not seem to be as commonly available as the larger red one used in the first version.
Also, definitly check the gears. You may be better off getting a couple of complete gear boxes.
HI All,
I know it is belated but thank you everybody for your inputs. I tried several times in the last week but there seemed to be a problem with posting over the week.
Seems that the worm is not meant to be a separate part but rather the truck? I should be able to measure it up and perhaps turn one from a plastic screw, once I have the size right. I have not checked the truck yet to see if anything else is stripped within so there was not much point in doing anything ordering parts... if they are around!
As it turns out, thanks to Soo Line Fan, I have found I have the second type with the open motors except I replaced mine with Mashimas,
Thanks again everybody
Regards from Australia
editor/publisher Railway Modeller Australia
and 2 are the revised version:
https://www.hoseeker.net/assemblyexplosionAtlas/Assembly%20Explosion%20Atlas%20FP7.jpg
The gearing is different as the original has 10T worm gear with 5 gears in the box. vs 14T with 7 gears. The frames, trucks, motors, driveshafts are all different.
Even the body was revised as shown on the top of the page as they offered 4 different body options such as single/dual headlamp and W/WO dynamic brakes.
Here's a pair of originals for the first version: https://www.ebay.com/itm/374225867916
These fit the ones with a silver motor and large steel flywheel.
I did not know that there were two different worm gears for the FP7, I was of the belief that all the ROCO gears were the same in the FP7 and other ROCO built engines like the GP40, GP38, SD24, SD35 and FP7 that Atlas had built along with the Model Power FAs and Sharks, and the AHM C424. The worm from any of those would be interchangeable with the FP7. You can usually find these old engines at flea markets and E-bay at reasonable prices as a parts factory.
Also Con-Cor re-issued the GP's and SD's but I don't know if the worms were the same, but they did change out the motors, but the frames were crap and broke apart so these can be found cheaply as another parts source.
Rick Jesionowski
Rule 1: This is my railroad.
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The athearn BB worm is a different diameter than the roco/atlas. I doubt it would even engage the top gear in the truck properly.
Can you tell me if you see two screw holes or one in bottom of the frame in the fuel tank?
I ask because Atlas ran two different models of the FP7 over the years and the drivetrains are totally different. The only part interchageable between the two are the truck side frame assembly.
Check these out
HO Worm Gear Assembly, High Performance/New (1) | Athearn
Athearn HO Worm Gear with Shaft, Brass (6) [ATHG40063] - AMain Hobbies
athearn worm gear - Bing images
NWSL, has a great supply of the various worm style gears, but one needs to take careful measurements of the worm to be replaced to obtain a proper match to the present worm being replaced.
Don; Prez, CEO or whatever of the Wishram, Oregon and Western RR
I think the OP is talking about the worm, not the worm gear.
The worm is the spiral-threaded cylinder; the worm gear is the disk with the gear teeth that looks for the most part like a regular gear.
All the OP needs to do is measure the axial pitch (basically the distance between spiral teeth), diameter and length of the worm and find one that matches.
There's a lot more to matching worms to worm gears than just that, but for our extremely low power transfer requirements, that's probably enough.
There are standard sizes for worms that match to standard worm gears, but good luck finding out which standards apply to a particular model. Thats not generally published information by the vendors in our hobby.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
Worm gears are a common generic design enough that many will fit. Just need the shaft diameter and gear length. . Other like kato gears might be compatable Your biggest issue is going to be that shaft diameter.
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An optimist sees the light at the end of the tunnel
A realist sees a frieght train
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Hi All,
I have a pair of Yellow Box FP7's that for some reason have stripped the worm on each of their lead trucks. I have made a good one out of both using the rear truck of one to the front.
Given the parts are hard to get, doing a search I found an Athearn worm set that going on the idea that the gear and the bearing look about the same proportion, I am tempted to check out.
Has anyone else had this experience and if so what was the best replacement source for the factory part please if indeed they are still available?
TIA from Australia