Changing Heljan gears – Class 33 / Class 47 – link to You Tube video
Prepared by Steve Luck Originator RM22394
RM22394, Nov 15, 2017 posted:
Hi all….
I'll park this in the new section as a reference topic (cross linked to Hints & Tips)
These two videos provide a step by step procedure for changing split gears.
I would think other loco types are similar….
I've got permission from the author to post them in the Guild forum.
Randall
YouTube link to Heljan 7mm O Gauge Class 33 gear replacement https://youtu.be/vS8hLTyn7Xc
YouTube link to Heljan 7mm O Gauge Class 47 replacing split gears https://youtu.be/sPeDgD5L638
DLOS, Oct 9, 2017 – Thread Title: Heljan Gears, Post #41
….but a fellow 7mm modeller has made this request:
‘Please would somebody make up a table of Heljan locomotives and which gears are needed as a replacement….’
David L wrote about three types that might be needed:
- A 14 teeth, OD 8.0 mm, PCD 7.0 mm, width over teeth 5.0 mm, no boss
- B 18 teeth, OD 10.08 mm, PCD 9.0 mm, width over teeth 2.9 mm, boss 5.0 mm dia 0.9 mm deep
- C 20 teeth, OD 11.09 mm, PCD 10.0 mm, width over teeth 1.9 mm, boss 5.0 mm dia 3.9 mm deep
All with bore diameter 3.0 mm.
Jim Snowdon, Dec 4, 2017 – Thread Title: Heljan Gears, Post #101
… order of gears suitable for the Class 26/33, at £66 for a complete loco set, ie all four of the gears that engage with the worms. Each gear will consist of a brass worm gear and drive pinion, mounted on a steel shaft, as direct drop in for the Heljan product. Since there is little point in replacing only odd gears, I intend making them available only as sets of four. Lead time is advised as 6 weeks …
…. If you are interested, could you email me directly at james.snowdon501@btinternet.com
To start with, I intend getting only sufficient for 12 loco sets, just in case.
Sygrove15813, Dec 8, 2018 - Thread Title: Heljan Gears, Post #394
Hi Jim , please tell me what exactly is included in a 'set' of replacement gears .
Thanks ,
Maurice , Aquitrain .
Jim Snowdon, Dec 8, 2018 - - Thread Title: Heljan Gears, Post #395
Maurice,
A set is four of these -
- which is enough to re-equip a whole locomotive, applying the principle that if you have to take the loco apart to replace one, you may as well do all four at the same time.
The example in the picture is for a Class 26/33 - they are all similar, but differ in the number of teeth on each gear (annoyingly).
Jim
DavidL, Mar 19, 2018 - Thread Title: Heljan Gears, Post #349
… I have now managed to do some work on a Heljan bogie. Back in December I gave Peter Clarke some of the brass gears I had made on Heljan splined axles. Peter later reported that he had found it difficult to fit them, as one of the axles would not go into the axle hole in the side frame. Examination of this revealed that the end of the axle had become slightly enlarged, as I had used a light hammer to force the splines through the hole in the gears. A few moments with a fine file soon cured that, and for all subsequent gear fittings I forced them on using my vice and a piece of steel with a hole in it.
The Peter reported that the mechanism was a little stiff, particularly in one direction, and got worse as the frames were screwed together more tightly.
Here is the bogie I was given to play with:
I don't know which model of loco it is from (apart from the fact that it is a Bo-Bo, obviously); I'll ask Peter tonight as it's club night and I plan to return it to him there. Close examination revealed that as the worm went one way it forced the worm gear away from the gear on the next axle, but as it went the other way it forced them into contact and rubbed. I hope the photos below show this.
First, with the worm turning anti-clockwise:
Second, with the worm turning clockwise:
I thought that a washer or collar on the upper end (in the above photos) of the axle with brass gears would keep the brass gear away from the Delrin one - in fact the photos show it with a thin washer in place, which proved inadequate. I made several collars from 5 mm brass with a 3.1 mm hole. in thicknesses of 1 mm +/- 0.25 mm, and the 1 mm one proved successful.
I also found that one of the axles with a Delrin gear on it seemed to be bottoming in its hole, and when the sides were screwed together it jammed solid (absolutely no idea why this had not shown up before, I can only assume that the axles got swapped over and the axle lengths and hole depths vary slightly). A few strokes of a file on the end cured this.
The mechanism now moved more freely, but it was obvious that the larger brass gear to the right of the work was bottoming on the part-circular recess it sat in. I put the relevant side in the milling machine and machined the recess about 1 mm deeper using a 7/16“ end mill; I think this should be obvious in the photo below as it is shinier than the surrounding metal.
At last, when all was screwed together, the mechanism worked freely in both directions.
I mention these various rather trivial problems in some detail as they are the kind of thing which may happen to anyone who is swapping gears, whether Heljan replacements or the one Jim has sourced (well done again, Jim). They just require a bit of common sense and a few basic tools to sort out (well, milling out the recess in the last bit would be a little trickier with hand tools, but the gear could be thinned instead).
Any questions, I would be glad to try to offer suggestions.
David
