Advice Needed: Getting a chassis to run

[Jim de Griz]

I’ve been building a J69 for a while now and generally come to the conclusion that the skills and toolkit I built up building airfix kits is not as applicable to building brass loco kits as I would have liked.

But, then part of the goal here was to learn new skills etc….

I managed to get to the point where the gear box and motor was in and the rear wheels turn, but now I’ve put the connecting rods on and progress has come to a halt.

With some adjustment I managed to get a quarter turn out of the wheels before jamming, but thats it. Taking off the connecting rods to the motorised wheels shows that the forward wheels will turn, but not freely. Frankly they don’t turn that freely with the rods removed….

That, along with other observations, leads me to a couple of conclusions

• The wheels are not on straight, nor can I get then on straight by hand

• The axles are no longer perfectly parallel (assuming they ever were) and the tin hat bearings are rubbing excessively on the axles

• The crank pins are a more or less perfect fit into the connecting rods with zero play

• Everything I am trying to do to correct the above is doing more harm than good

Thus the request for advice. I’m not sure how to correct the above, I’m not sure what tools I require to correct the above. I’m perfectly happy to disassemble the mechanism right back to the frame if that is what is required, but at the minute I have no confidence that the result would be an actual improvement.

Any help/advice the forum members could offer would be much appreciated.

Jim de Griz

[Mersey508138]

Hi Jim

The 1st thing to check from what I have read on other forums ( rmweb in particular as a lot of the members are kit builders ) is to have 1 wheel on any given axle to be used for testing purposes and to spin the wheel by hand ideally before fitting the motor ( as I have not yet built a oo loco kit it is highly possible that members who have may well correct me so everything I am writing here could be subject to modification by members more in the know than I am ) and see how well it rotates.

If there is any binding as could be the case here, remove the wheel and using a round file of suitable size, gently file the bearing or use a reeming tool to open it up just enough ( a lot of trial and error required here ), this needs to be done on all 3 sets of bearings.

Another thing I have read a lot is to also open up the coupling rods a little as they can also bind on the crankpins ( don't forget to add a bit of oil to the wheel bearings and the crankpins as this will aid with the testing process aswell.

Continue adjustments to the wheel bearings and coupling rods until everything turns freely once fitted in place and always start at the low end of the power just enough to get the wheels to crawl speed and if all is ok and a full rotation is successful with no binding then the power can be increased until the highest voltage the loco will operate at is reached and leave it to run in aswell as checking lubrication and adding oil if required.

The only loco kit I have built is the O Gauge Scotsman loco that was produced by Hachette back in 2008 / 09 and some of the parts in that required very little modification while others required a bit more to get them to fit ( pictures of this loco appear in my thread in the introductions section of this forum ).

I'm hoping my tips are correct and potentially useful but I'm sure there will be some details I may well have missed.

[jwealleans]

I think back to the frames is what will be required here if the axles aren't square and parallel. Those also look like Gibson wheels: I won't touch them while Romfords or any other self-quartering wheels are available.

Strip it back to the bare frames. Did you use a jig to put the frames together? It really helps, though it's not essential. if yuo don't have one, get some 1/8" rod and put a longish (6"-9" length) through each pair of bearings. That should show you if they're parallel, especially if you place the frames on one of those cutting mats with a grid marked on it. You then need to adjust the frames until they are - either resolder them so the axles are all parallel or adjust individual bearing holes until they are.

Once they're happy that that's done, put the wheelsets back in and make sure it all runs freely. You might need to use a reamer or even gentle filing to ease the bearing holes and also polish the axles if they've tarnished or even rusted. The assembled frames should run up and down on your bench or some track as freely as any rolling stock. That way your motor will be fighting minimal resistance to get it moving.

I then put crankpins in and fit one coupling rod. Don't attach it, just slide it over the crankpins. Roll the chassis backwards and forward again. If there are tight spots, look to see which pins are binding (you can tell if they're pressed hard against the front or back of the hole) and elongate that hole gently with a very small file. You only need a few strokes, you're removing thousandths of an inch only here. Keep doing that until the wheelset rotates freely with the rod in place.

Repeat above for the other side. Then fit both rods - you can use blutak or the sleeving off fine wire to hold them in place - and roll the frames backwards and forward again. When they bind, if they do, decide which rod is causing it (the other one will be slightly loose on the crankpins) and then which hole and gently open that one out a fraction further. Repeat until you have free movement in both directions. This can take a whole evening, but don't be tempted to rush.

Only when your chassis rolls freely with both sets of rods in place should you think about putting the drivetrain in place and powering it.

Hope that helps - that's how I do it. Others may have different approaches.

[Hatfield Shed]

The above advice is good.

As to the design of the mechanism you are assembling, if it is possible I heartily commend using at least a two stage gear train rather than direct drive of the worm onto the axle gear. It's no casual accident that every good RTR OO model mechanism is now made like this.

[mick b]

If you are Gibsons? you need a GW quatering jig to ensure the wheels are 90 degrees from each other on each side.You can quarter by eye but far from simple. How have you fitted the wheels to the axles ? again use the GW jig it will get them on straight.
Is their any clearance on the Rods holes , you need them at least 0.5mm larger than the crankpins as a start or nothing will ever move . You can then adjust any tight holes in the rods when the wheels are turned over by hand . Never try and run the motor first .

[Atlantic 3279]

Did you mean 45 degrees Mick?

It's not impossible to get single stage gears to mesh nicely (smoothly and quietly, for both directions of travel) without the aid of a proprietary gearbox, but it can require a bit of time, patience, observation, deduction and various adjustments.

[Jim de Griz]

Thank you all for your advice.

So, looks like its a right back to the frames job, maybe even a disassemble the frames and start again job because I suspect even with the motor and coupling rods removed she will fail the free running tests that Mersey and Jwealleans suggest. Incidentally is a jig for this sort of job something I buy, or something I make?

I'm afraid the wheels are Gibson's, they were the only ones available in the right size/spoke combination when I brought the kit. They are still a tight fit to the axles, but I'll be damned if I can keep them straight. Do I need to replace them? The GW Quartering Jig sounds interesting, but seems not to be the easiest things to buy? I could definitely do with something to help me get wheels on straight (as my experience with the B12 attests)

The crank pin holes have zero clearance, two of them had to be opened up just to get the pins in....I assume I need some sort of reamer to open them up? I assume I need one that is tapered to open up the hole and a parallel one so I can file the hole to a uniform profile? (On the subject of the con rods, should I have assembled it as one solid piece? The instructions imply I leave the two halves separate, but I think I might be misunderstanding)

About the gear box. I originally dropped from 2 stage to a single because I was having an absolute git of a time getting the 2 stage to fit in the limited space available. The single stage helps in that respect, but it puts the motor between the frames, which has bowed them a little, which is probably not ideal. Would certainly be happy to try a 2 stage again, but does anyone have any advice on which I should try, it needs to be fairly narrow and fairly low.

Jim de Griz

[mick b]

High Level Models for the gearbox. various versions available. On the internet.


GW models are on the phone only
G W MODELS
Specialised Tools
11 Croshaw Close, Lancing, Sussex, BN15 9LE
Telephone 01903 767231

Wheel Press & Quartering Jig for 3&4mm fine scale wheels £28 ea

This is from 2019 no idea of current price.

You will probably have to buy new wheels as Gibsons do not like being pulled off and they tend to go back on crooked . Scalelink do Markits Wheel copies much easier and cheaper as well.

https://www.scalelink.co.uk/acatalog/Lo ... eels_.html

[Mersey508138]

I recommend markits locomotive wheels, much easier to work with.

[Hatfield Shed]

...The single stage helps in that respect, but it puts the motor between the frames, which has bowed them a little, which is probably not ideal...

Actually beyond not ideal, but likely to be a contributory cause to the trouble you have.

To explain, when correctly profiled etched frame kits started to replace 3/32" plain brass strip frames, it was quickly discovered that more attention had to be paid to body attachment to avoid distorting the frames to any extent. An assembled etched frame mechanism which ran beautifully on its own would develop troubles such as a bind with the body mounted, because it was being slightly deformed: more attention was required to make sure that the body solely exerted a vertical load on the frame attachment locations.

[jwealleans]

The above, absolutely. I've built two Crownline J19s and both developed a slight twist in the body, so the fixing screws to the frames have to be left very slightly loose or they run like a sack of spanners.

[earlswood nob]

G'day all

I was a solid Markits fan (when Mainly Trains were about), but since then Markits have slowed down their supply has got very expensive.

I now build the chassis using old Romford/Markits wheels. Then at the last moment I switch to Gibson wheels, using a GW press to get the quartering right.

BTW I still build locos, with the wheels on one side made non-insulating by shorting out with very fine wire.

Malcolm (Earlswood Nob)

[Jim de Griz]

High Level Models for the gearbox. various versions available. On the internet.


GW models are on the phone only
G W MODELS
Specialised Tools
11 Croshaw Close, Lancing, Sussex, BN15 9LE
Telephone 01903 767231

Wheel Press & Quartering Jig for 3&4mm fine scale wheels £28 ea

This is from 2019 no idea of current price.

You will probably have to buy new wheels as Gibsons do not like being pulled off and they tend to go back on crooked . Scalelink do Markits Wheel copies much easier and cheaper as well.

https://www.scalelink.co.uk/acatalog/Lo ... eels_.html

Thanks Mick, that is all very useful. I'm getting the axles with flat is for the axle with the gears?

...The single stage helps in that respect, but it puts the motor between the frames, which has bowed them a little, which is probably not ideal...

Actually beyond not ideal, but likely to be a contributory cause to the trouble you have.

To explain, when correctly profiled etched frame kits started to replace 3/32" plain brass strip frames, it was quickly discovered that more attention had to be paid to body attachment to avoid distorting the frames to any extent. An assembled etched frame mechanism which ran beautifully on its own would develop troubles such as a bind with the body mounted, because it was being slightly deformed: more attention was required to make sure that the body solely exerted a vertical load on the frame attachment locations.

That is very useful to know and adds another vote to the likely need to take the frames apart and rebuild them after flattening everything.

Jim de Griz

[Jim de Griz]

Once more, thank you everyone for the advice.

Current Plan of Action

• Remove motor, gear etc and test axles for running/alignment

• If as I suspect the frame isn't assembled correctly, disassemble and strip paint etc

• Acquire suitable reamers etc, new gear box, new wheels, new bearing etc

• Find long weekend I can concentrate on reassembling the frames

The last might take some time, but I know me, I need to find the spare time or I'll be too tempted to rush it and make all the same mistake again.

Jim de Griz

[mick b]

High Level Models for the gearbox. various versions available. On the internet.


GW models are on the phone only
G W MODELS
Specialised Tools
11 Croshaw Close, Lancing, Sussex, BN15 9LE
Telephone 01903 767231

Wheel Press & Quartering Jig for 3&4mm fine scale wheels £28 ea

This is from 2019 no idea of current price.

You will probably have to buy new wheels as Gibsons do not like being pulled off and they tend to go back on crooked . Scalelink do Markits Wheel copies much easier and cheaper as well.

https://www.scalelink.co.uk/acatalog/Lo ... eels_.html

Thanks Mick, that is all very useful. I'm getting the axles with flat is for the axle with the gears?

...The single stage helps in that respect, but it puts the motor between the frames, which has bowed them a little, which is probably not ideal...

Actually beyond not ideal, but likely to be a contributory cause to the trouble you have.

To explain, when correctly profiled etched frame kits started to replace 3/32" plain brass strip frames, it was quickly discovered that more attention had to be paid to body attachment to avoid distorting the frames to any extent. An assembled etched frame mechanism which ran beautifully on its own would develop troubles such as a bind with the body mounted, because it was being slightly deformed: more attention was required to make sure that the body solely exerted a vertical load on the frame attachment locations.

That is very useful to know and adds another vote to the likely need to take the frames apart and rebuild them after flattening everything.

Jim de Griz

Re
"Thanks Mick, that is all very useful. I'm getting the axles with flat is for the axle with the gears?"

Not sure what you mean? If you use Gibsons you will need to file a flat on the drive/geared axle .I you are using Markits you can buy a axle with the flat already made, or again file a flat on the driven axle.