7mm Fixing Split gears on a Heljan diesel

[pricei]

Richard, thank you.

As yet I have not been able to find any of the gears on the driven axles... nor have I got a definite answer as to the necessary part number. I have worked through the parts diagram for most of the Heljan diesels (see Gaugemaster Download Instructions web site) and I think that the required part is described as "0.5 x 16T x 5L x 2.9mm" and that description appears in at least six of the loco parts diagrams... however, Gaugemaster say that there is no stock of that gear under any of the six stock item codes / associated barcodes in the HJ parts price list.

I am now considering the use of an Ultrascale gear for the driven axle, this part. What does the team think about mixing brass and nylon gears? And yes, I am aware that all HJ 7mm diesels have a brass gear on the motor shaft...

Although expensive, the possibility exists of replacing all of the HJ nylon gears with Ultrascale equivalents... is this an option worth considering?

regards, Graham

I had to replace split nylon gears on an early class 33 and used Ultrascale brass replacements - they work fine. They weren't cheap but at the time I couldn't get nylon replacements from Heljan. I also had a class 26 with the same problem so I bought two sets from Ultracsale - the same gears fit both a 26 and 33.
Ian

 

[Dog Star]

To recap on our experience in regard to Heljan diesels with split gears, possibly true for many of the early HJ models and less so for more recent production - I do not know when HJ introduced design changes to the gear trains, we have a Cl.26 that has suffered with split gears, a Cl.31 that does not yet, and several of the recent Cl.37/4 models which do not yet show the click-clack / lack of movement symptoms. Maybe others can point to the time when HJ production introduced the change to the design of the gear cluster which transfers power from the motor to the gear train.

This post summarises our experiences with a Cl.26 model following on from Richard's (@richard carr) original post to this topic. Peter (@Spike) and I thought, initially, that the symptoms of our model were the same as reported by others - clicking from one or other of the bogies and a lack of movement. Removing the cover plate of the bogies showed that all of the cluster gears had splits in either the spur gear that meshes with the worm wheel (on the motor shaft) or the pinion gear that meshes with the gear train (between the bogie frames). Richard's original post provides the part number to use when ordering the replacement parts from Gaugemaster. The original HJ design has two separate gears on one shaft with power being transferred between the gears by means of splines on the gear shaft, the revised HJ design has the two gears moulded as a single entity and hence the design can suffice with a plain shaft.

After replacing all four gear clusters we re-assembled the engine and applied power... this time one bogie provided intermittent motion and the second bogie continued with the clicking noise. Time to remove the cover plates again and inspect all of the gears in each bogie. The source of our problems appeared to be with the final drive gear - a spur gear on another splined axle... we had three split gears across the four final drive axles (Cl.26 being a Bo-Bo with drive to all wheels). Gaugemaster was of no help with replacements - either individual gears or complete wheelsets. Time to look somewhere else and Ultrascale came to mind.

Ultrascale has an appropriate gear, see here. Just so bar the fact the Ultrascale gear has a smooth bore of 3mm whereas the HJ axle is of 2.9mm diameter and splined. A telephone conversation with Colin Dowling (@eastsidepilot) concluded that a probable solution could be to use a 3mm diameter rod of Silver-steel with the replacement brass gear secured by Loctite. I sent the four wheelsets of our Cl.26 to Colin who followed through on our conversation, we received in return four wheelsets with Ultrascale gears on new axles (wheels set to S7 B2B). Thank you Colin.

Here is a photo showing the upgraded wheel sets before and after fitting to a HJ bogie.








The black gear clusters are the revised HJ design, parts which we obtained from Gaugemaster.

regards, Graham