Update on S7 diesel wheels
1. Heljan utilise an unusual axle diameter of 3mm.
2. Malcolm makes axles with a screw on wheel at one end with 3/16" diameter axles and he cannot go down to 3mm and still leave enough metal to have a secure thread to retain a wheel and also to provide a shoulder for the wheel to screw up against and thus provide the correct S7 gauge width and correct back to back.
3. Heljan use an impressive plastic gear train / gear box that ultimately drives an axle gear, this gear obviously has a 3mm internal diameter, that permits a force fit onto a knurled section in the middle of the axle. This gear and the wheels can be pressed off the Heljan axle, but the gears would then need to be fitted to replacement knurled 3mm axles.
Malcolm has advised me that there is not even enough interest to just commit to the production of S7 diesel wheels on 3/16" axles, (which in any event could not easily be fitted within Heljan bogies).
I hope that this information helps to update those interested in understanding where we currently are at and it must be viewed as a work in progress so far as Heljan diesels are concerned. However, the S7G is now proposing to commission production of 3ft 9in S7 diesel wheels. Which axles these will fit I am not yet clear on and it is perhaps a case of watch this space
An alternative for getting Heljan diesel wheels turned down to S7 standards is of course to use Colin Dowling, who has an excellent web site at www.eastsidepilot.com
Colin has had some good words said about hm and the work that he undertakes on the independent 'Western Thunder' web site, (Google it and you can visit the forum site without actually joining and thus read the posts). Colin has copies of the BR wheel profile drawings and on the WT site he mentions the re-profile sizes and how he does the work, complete with photographs. On the WT site just put 're-profiling Heljan wheels' in the search section and it should come up.
You can take existing wheel sets out of a Heljan diesel by carefully placing the loco on its roof on a table (support it on both sides and underneath with some soft faced material) and then taking the small screws out of the flat keeper plate over the base of each bogie. With that out of the way, you just pull with a slight wiggle on each individual wheel set and out they come. Put them in a jiffy bag and send that to Colin with a cheque / money order etc. I am not sure of the exact cost, but it of course cheaper than a new set of wheels!