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hayfield

Alan Gibson hornblocks and mainframes

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7 hours ago, hayfield said:

One step forward and about 3 back

 

https://www.rmweb.co.uk/community/uploads/monthly_2019_11/978.jpeg.eedef67d4aa1e9f056c488d7e6c594fb.jpeg

 

It took me ages to get the first hornblock fitted but go easier with each one. Trouble is the springs seem too strong, wheels are all over the place quartering is now out and definitely lost its free running charistics

 

I will take the chassis back to its state last night, where it was free running, Firstly see if the quartering is OK. Then figure out the springing again.

I have used the Gibson sprung hornblocks on a couple of chassis.  The main reason being that you can drop wheelsets in and out just like many RTR chassis.  I don't like disassembling Gibson wheels once fitted square on the axle....  Because they project inside the chassis they do somewhat limit the gearbox width.  OK for P4 but I had some trouble with an O-16.5 chassis.

 

The normal setup for 0-6-0s is to level the chassis using the outside adjusting screws then unscrew the centre axle screws to allow a little upward movement.

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20 hours ago, hayfield said:

as the milled cutouts seemed to fit the coupling rods fine.

 

As we are dealing with some small tolerances between a free and stiff chassis, I am not sure how you can establish this without using the jig to assemble the chassis.  

 

I have never encountered a problem when soldering with 145 degree on my Hobby Holidays jig.  One solution to the heatsink issue is to solder the side away from the main body of the jig first, take the chassis off, flip it and solder the other side.

 

Another thought is that with an all horn block construction, the wheelbase is a moveable feast as things move up and down, so you will need to open out the rods slightly.  However, looking at the pics, you appear to be using the Romford crank pins which IIRC are about 1mm whereas the Hobby Holidays jig is designed to use 1.5mm rod holes so I am wonder whether the jig was setup using these rods?

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Brassey

 

Thanks for the reply, yes I used these coupling rods when setting up the jig, and am using Romford wheels until I am happy with the chassis. As it happens the kit of bits never had any coupling rods, these are of the correct size and came from my spare coupling rod box

 

I do think the main issue is from not using the jig and perhaps soldering the hornblock guides slightly out of square

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10 hours ago, cctransuk said:

 

All this 'floppy chassis' business seems to me to be making trouble for oneself; I'm with Tony Wright on this - give me a good old rigid chassis any time.

 

(..... and, yes - I have built compensated and sprung chassis, but they were a lot more faff and didn't run as well as my rigid ones).

 

Regards,

John Isherwood.

 

I might be coming round to this way of thinking, as I said its a test bed for me and I always thought it would be a big learning curve. Having said this I made a flexi-chassis many years ago without any jigs !!!

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But Tony Wright is building for 00. For P4 you need to employ different techniques to rigid. I have a feeling this chassis is EM?

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12 hours ago, cctransuk said:

 

All this 'floppy chassis' business seems to me to be making trouble for oneself; I'm with Tony Wright on this - give me a good old rigid chassis any time.

 

(..... and, yes - I have built compensated and sprung chassis, but they were a lot more faff and didn't run as well as my rigid ones).

 

Regards,

John Isherwood.

Interesting, my experience is the complete opposite! I just can't  get all the wheels in contact with the rail at the same time, I need the flanges to keep the vehicle on the track. For me, compensation works much better.

 

Cheers

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1 hour ago, PenrithBeacon said:

Interesting, my experience is the complete opposite! I just can't  get all the wheels in contact with the rail at the same time, I need the flanges to keep the vehicle on the track. For me, compensation works much better.

 

Cheers

 

David

 

Using my Hobby Holidays chassis jig it is very easy to get a rigid  chassis square simply by first fitting the bearings into the sides, then using the same chassis to keep both frames square whilst soldering the frame spacers together.

 

The problem I am facing is the fact that there seems to be quite a lot of slop between the horn block guides and hornblocks, which should be taken up by the U shaped wire which acts both as a guide and retaining strap

 

I do to have 2 other styles of guides one being the MJT another being a London Road type, I will see how I get on 

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The bearings should be a loose enough fit in the guides so that they fall out under their own weight but definitely not sloppy.  Were these acquire used?

 

Both the MJT and LRM types are unsprung so will need either some beam compensation or CSB setup.

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16 minutes ago, Brassey said:

The bearings should be a loose enough fit in the guides so that they fall out under their own weight but definitely not sloppy.  Were these acquire used?

 

Both the MJT and LRM types are unsprung so will need either some beam compensation or CSB setup.

 

Brassey

 

No the units were new, and as I said its down to how I have fitted them

 

I need to revisit the how I fitted them, as now I have a better understanding of how they are supposed to work

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If I recall from my 850 build the retaining wires on the Gibson sprung blocks don’t play any part in guiding the square bearings, the cheeks on the horn guides should do that. The bearings are not always square so try them in different orientation and mark them so you can put them back in the same orientations and hornguides.

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Not true, the wires go between the half grooves in both the hornblock and square axle bearing.  This effectively constrains lateral axle movement.

 

IIRC the grooves in the bearings are off centre allowing the outer bearing face to be proud of the hornblock which is meant to be flush with the frame.

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Apologies, evidently I didn’t appreciate that the wires had that effect. 

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