Bachmann 45xx conversion

[grovenor-2685]

I'd try an initial drill into the end around 1.5 to 2 mm and go in about 1 mm.
Like I said, this is ideas, not tested solutions
Perhaps above not clear, the 1.5 to 2mm I meant diameter of drill, might even be better using a centre drill if available.
This would then allow the drill for the pin to start in the bottom corner of the hole.
Keith

[Tim V]

Someone like to try it?

To finish this off, I found that after I'd fixed the wheels, that there was still a problem with poor running, I re-centred the coupling rods, using ideas from Chris Pendlenton's article in MRJ 200.

It now runs a lot better, there is a bit of roughness from the three pole motor, I might have a look to see if I can tune that out in the chip.

[Philip Hall]

I usually use a 0.6mm drill at least, and use a hand held Expo type drill. I start the hole in the centre of the end of the axle, once it's in a mm or so, keeping the drill running, I move the drill to about 45 degrees and press on until it comes out of the side of the axle. 0.6mm is not so fragile and I also have a foot switch on the drill so if it sticks I can turn it off quickly. Now this does work quite well but Tim's lathe work is a lot more precise and better engineering.

Philip

[Philip Hall]

Tim V wrote:
there was still a problem with poor running, I re-centred the coupling rods

I've just (literally) finished an EM one of these and I had the same problem with axle slots not at right angles to the frame casting, but this one was only like that on the middle axle! The rods on one side were spot on as supplied (?) but I had to move the centre of the other side by about 0.5mm. All the wheels sit on a surface plate quite nicely - well the middle ones are a fraction off the deck, the sort of thing advocated before we thought of things like suspension. If the manufacturers can work to that sort of precision (as far as getting it level is concerned) how on earth they get the axles crooked is beyond me.

And we are trying to tell people that conversions are easy! But it now runs very nicely indeed...

Philip

[martin goodall]

You may remember that this was the problem I encountered when I attempted to convert a Bachmann 45XX to P4. I mentioned it in a previous thread (but it is now lost in the mists of time.)

My 45XX is still languishing in its box, waiting for me to get a round tuit.

I am not sure I understand what Philip did to 'tweak' his Bachmann chassis. Perhaps I should refresh my memory as to Chris Pendlenton's article in MRJ 200 - does that give the answer?

[Tim V]

Sounds like Philip is dealing with a different problem on his chassis, I recentred the rods, while he's moved the axles.

[Philip Hall]

Tim,
Sorry if I gave the wrong idea, I did re-centre the rods, but only on one side (!) I did think about the chassis slots but got frightened.

Martin,
Here's how I re- centred the rods:

I laid some 'jig axles' in the slots in the chassis and clamped them in place with the keeper plate. I use the LRM taper ones; it doesn't matter that they're 1/8" as they rest in the top of the slots - this is quite useful as there's no slop in them as you're fiddling with the rods. 3mm ones, if you could get them, would slop around in the slots and not give you much of a datum.

In my case I found that the leading and trailing axles were OK, it was the centre, driven one which was not at right angles. I pushed conversion bushes into the rods and dropped them over the tapered axle ends, which showed that (in this case) the overall end to end dimension was OK for both rods, but on one side of the chassis the centre hole in the rod needed to be moved to one side by about 0.5mm or maybe a bit more. On the other side all was well, so I just soldered the bushes into place, reamed them out a bit to a running clearance, which on a RTR chassis I usually find is 1.6mm. On the dodgy side I soldered in the bushes fore and aft and then filed out the centre hole in the rod so that the bush could be slid to one side, checked on the jigs again, finally soldering it in place, allowing a little excess solder to fill in the gap left to one side of the bush. Then I cleaned up, checked all was still OK, reamed out to 1.6mm again, fitted it all together and it ran! On this occasion I didn't slim down the rods and bosses so that was it. Apart from...

A word of warning, though. After I've fitted the final drive gear I always pin it to the axle. Bachmann are a much tighter fit on the axles than Hornby, but whatever, I don't trust cyano and I don't want things coming adrift later. So I did in this case, but forgot to trim the pin off flush where it goes into the boss of the gear, just snipped it off and left it a little proud. Every time I tightened the keeper plate, there was a knock from the wheels every revolution. And then I remembered on the last one I did a year or two back that I had the same problem. It was the pin scraping the little recess on the keeper plate for the gear. Trimming the pin off flush solved the problem. I suppose a better memory would have helped, too.

Another problem was that the footplate didn't want to sit quite level and I solved that one with some careful paring of the top of the slidebar brackets and packing of the back of the chassis from the frames. Much depends on the fit of these items in the first place, so it's a problem not all folk will have. That won't apply to the 4575 I'm building for 'Mellstock' as I'm going to beef up the slidebars and modify or replace the brackets. Depends on how much you want to do.

All this lot is probably a very good advert for building a new chassis!

Philip

[Tim V]

Funnily enough, I used 1/8" axles for the same reason as Philip. I was using the Ultrascale conversion set which has their gearwheel, and I used their crankpins as is.

The improvement in running was well worth the effort.

[Philip Hall]

Just a note to say that I re-read my last post and some of it no longer made sense to me, so I've altered some of the wording when talking about the rod adjustments. Hope it now makes more sense.

Philip