Re-gauging Heljan locos to S7

Richard,

I'm just using a simple (ground for brass so it does not dig too deep) lathe tool as opposed to the one ground for Slaters steel rims. The nut does hold the work perfectly well......so far. There's enough 'grip' between the holder and wheel face to allow you to cut 2-3 thou off each pass but you do need to make a small dish in the centre of the holder to take the Heljan wheel boss which sticks out by a few thou.

No soft jaws at all, wouldn't even know what they were if they bit me on the ankle, soft jaws for a vice, yes, but a lathe?

It's all very un S7 to be honest, the correct way would be to use a form tool to get the correct wheel profile but I work on the principle that if it rolls through Love Lane then that's good enough for me

All I do is take 15 thou off the back of wheel, then I take 15 thou off the flange and just round the flange off with a file (I tell everyone it's a special S7 file...but shussss it isn't really ) and then some fine abrasive paper, S7 of course, y'all can probably guess right now I don't take it too seriously LOL.

I do not touch the tyre cone or angle or rim face, just the back and the rim edge, all very school boy I know but looks the part (except to those with micrometer eyes) and works very well so far on both the Class 26, A1 tender, Fowler 4T and Std 5

Hope that helps

Mick

Mick

If it works that's all you need to do.

Soft jaws are chuck jaws made from mild steel they can be easily machined and I use them to hold wheels by the tyre by machining a 1mm rim into the face of them. They hold the wheel perfectly concentrically as the jaws are machined in situ on the lathe chuck. These are essential for machining wheel castings and I use them for reprofiling too.

I'll post some pictures when I'm back next week.

Richard

richard carr said:

Mick

If it works that's all you need to do.

Soft jaws are chuck jaws made from mild steel they can be easily machined and I use them to hold wheels by the tyre by machining a 1mm rim into the face of them. They hold the wheel perfectly concentrically as the jaws are machined in situ on the lathe chuck. These are essential for machining wheel castings and I use them for reprofiling too.

I'll post some pictures when I'm back next week.

Richard

Click to expand...

Richard, apologies I didn't see your last reply, thanks for the info, I'll look at trying to get some of these for my C3 lathe, mind if this Chinese lathe steel is anything like our cranes, then it'll be 20% butter already and plenty soft enough for machining

Mick

Here are some photos

The first is the lathe chuck with the soft jaws fitted ( I rarely use anything else these days) you can see how I have machined 3 steps into the face of the them.



Now I have added some wheels these are the excellent class 37 wheels that Rob Thomson has been selling



You can get a very tight grip on the tyre without marking it.

You can even hold wheels by the flange



Soft jaws are readily available from engineering suppliers but you must make sur you get the right ones for your type of chuck.

Richard

Heljan wheels are notoriously coarse and the coning is non existent ( Flintstone wheels ) and need refining even for F/S let alone S7.
My method for re-profiling Heljan wheels to S7 is to skim 0.25mm off the back, down as far as the boss in this case, to bring the flange width down to 0.75mm.
This gives enough metal for the profile tool to cut.
I do this by putting the wheels in a set of soft jaws gripped by the tire.


As I do quite a bit of this I have turned up some mandrels to suit the wheel dia's. and some stub axles to mount the wheels for re-profiling. The stub axles helps keep the wheel on centre, while the mandrels grip the wheel by the tire. This method avoids any slipping of the wheel occurring but if the cutter should accidentally jam then the whole lot will spin ( said he hitting the big red button ) . This is all done in the conventional set of jaws all held up tight with a revolving center in the tail stock.



Once re-profiled the wheels are then re-mounted in the soft jaws gripped by the flange this time and the face skimmed off to reduce the tire to your desired width, usually on loco's approx. 3.2mm, but check your prototype G.A. if you are that particular. Certainly in S7 it can some times be important, if you've built a highly accurate model, that there are no problems with clearances.
Once skimmed down all that's left is to take a bevelled cut on the outer edge of the tire. In reality this is only about 5/8" x 3/8".

Below are B.R wheel profile diagrams.



Above, Flintstone wheel to the left, re-profiled S7 wheel( face not machined yet) to the right, .......obvious really.

Col.

Never spotted the coning...or lack of I haven't seen any issues with mine without coning so I'll let sleeping dogs lie, but will see to it on the next model

Having said that, I just rechecked the class 26 and compared the coning with a Slaters wheel and they look about the same but the coning doesn't look 100% consistant over all eight wheels.

I didn't take anything off the face so ended up with 3.45mm wide wheels, a little too much full fat bacon for breakfast but I did take more off the back (0.38mm) to end with thinner rims, that might bite me later!

Handy info on tyre profiles, will file that away for a rainy day....ohh it is....having driven through it all for the last two hours back from London!

Mick

The main reason we need thinner wheels is so that they fit properly in the bogie, clearances are pretty tight onthe real thing as I'm sure you know from your class 40 bogie, so Heljan clearly have overwide bogies as not only do over thick wheels fit but there is masses of sideplay available too, there is next to no sideplay on a JLTRT 37 bogie even with correct thickness wheels.

Richard

Richard, indeed, and that's probably why the ploughs don't fit very well on the class 26 as the corner of the bogie fouls them on corners, resulting in many I've seen being bent forward to clear the bogie. I was going to make some new brass ones up along with new brackets anyway but narrower bogies would help as well.

Being as I still have plenty of side play I'm not overly concerned about the extra 0.25mm width I currently have. If and when I reduce the bogie width along with the fuel tank width I'll leave them with just enough clearance for the current wheels, I don't really want to keep pulling them on and off the axles, but next time I will

I know what you mean about JLTRT bogies, especially the class 40 with it's resin sides which should be plate steel thickness, hence my etched ones and the correct joggle inside and outside at the front will help sideplay on the pony truck I hope. Maybe even the 37 bogies are too thick, thicker than the real thing? which is causing people issues in S7

Real locos are very close, can't recall the 66 clearance....but can check today, I suspect theres quite a gap as the primary suspension is designed to float due to the self steering facility....but, the 08 is silly tight, so tight that the leading and trailing wheels often touch the outerftames and leave rub marks on the wheel rim.

Does anyone offer a re profiling service on the Heljan Class 40 wheels to improve running on standard 32mm track? I am sure I saw a service to tidy them up (not S7)
I have adjusted B2B but I think the flange thickness is a disaster.

Cliff

Colin Dowling (Eastside pilot) can do it for you he as a very nice finescale form tool for the job.

Richard

Cliff,
Yes as Richard says this is a service I can offer, send me an email and I'll give you the details .

Col.