Dettingen GCR might have been layout

[micklner]

JW

 

    Is the Pivot arm free to move at both ends? . How is it fixed/located onto the front screw ? Any spring at the Bogie end ? Is the Bogie still removable ?

 

Thanks for the photo and drawing .

 

Mick

[ian@stenochs]

18 hours ago, jwealleans said:

 

Here you go, Mick.   The arm pivots on the bolt you can see at the front of the cylinder and then attaches to the bogie centre where you see the nut.   This is how you work out the pivot position:

 

 

 

 

I used a similar set up on a Duchess I built in S7. The beam pulled the rear bogie wheel forward away from the brake hanger on curves. As it was 7mm scale, with a bit more mass, I added a light tension spring which pulled the bar straight and gave a self centering effect which helped steer the engine into curves.  

Sorry I don't have a photo.

Ian.

[jwealleans]

17 hours ago, micklner said:

Is the Pivot arm free to move at both ends? . How is it fixed/located onto the front screw ? Any spring at the Bogie end ? Is the Bogie still removable ?

 

Morning Mick,

 

Yes, it is.   There's just a nut on the fixed screw with Tacky Wax to stop it unscrewing.   No springs, the bogie just stays on the track through it's own weight.   It does all unscrew and come apart if necessary

 

[Clive Mortimore]

20 hours ago, richard i said:

Looks interesting. I am guessing the 3/8th comes from when all the measurements were done in imperial.

that has got the cogs whirling.

thanks

richard 

Richard, have a chat with your scientist wife.

 

3/8ths is a ratio. So if your wheel base, X, is 30 mm long you multiply by 3 then divide by 8.

3x30=90

90/8=11.25

 

Therefore the swing arm pivot points, A and B, are spaced at 11.25mm apart.

[gr.king]

For those who collapse in terror at the sight of a fraction such as 3/8ths, just multiply by 0.375, or ask a gadget to do it for you.

[billbedford]

That is inordinately precise for a model railway bodge.

 

How about - The swing link has to be long enough to clear the bogie's leading axle or headstock and the fix pin should not foul the loco's buffer beam. 

Edited February 26 by billbedford

[ian@stenochs]

2 hours ago, billbedford said:

That is inordinately precise for a model railway bodge.

 

How about - The swing link has to be long enough to clear the bogie's leading axle or headstock and the fix pin should not foul the loco's buffer beam. 

 

Just remember that a short swing link will pull the bogie further forward than a long one. 

 

[Jol Wilkinson]

A bogie retaining link has the same effect as a radial (curved) slot. The front mounted link has the effect of moving the bogie pivot point forward as the bogie moves sideways, the opposite with a rear mounted link (the normal configuration).

 

Other than possibly providing additional clearance to chassis mounted fittings such as brake gear, the fore or aft displacement will be relatively small unless on very sharp curves so it is difficult to envisage what other benefits there are.

[richard i]

5 hours ago, gr.king said:

For those who collapse in terror at the sight of a fraction such as 3/8ths, just multiply by 0.375, or ask a gadget to do it for you.

No fear of fractions, just noting that imperial measures break down into 12th 32nd or 64th so guessed that is where it came from. 
richard 

[billbedford]

The Atlantic frames were tapered by 3 inches in front of the smokebox. So by slightly exaggerating the taper and moving the bogie pivot back, you should be able to get enough movement in the bogie to clear the frames and cylinders. 

[richard i]

Holiday project.

have to travel light as need to get 5 peoples luggage and a dog plus it’s luggage in a car. 
able to fit tools glue and paint to make this. Tree branch free of charge off the ground. 
placed on the layout. It needs a driver, at some point I will need to admit there is no more space for cars or carts. They will have to become wagon loads.
work on the Atlantic can slowly resume. 
Richard

[richard i]

A big step. Major components fitted together.

Now whispering it quietly I think it has all been designed for p4. It has needed fettling to get this far and it looks like it needs some space made around the bogie wheels on the frame. 
decision time, cylinders or the small items on the body next?

 

it certainly now feels like this loco will get finished. Something I have not always thought.

richard 

no need to discuss the light reading behind. An occupational hazard/ necessity.

[Caley Jim]

1 hour ago, richard i said:

decision time, cylinders or the small items on the body next?

I always like to get a loco in working order before I start adding any details. 

 

Jim 

[jimwal]

Get the chassis up and running with motor, gears and pick-ups. Coupling rods, cylinders, slidebars connecting rods and valve gear if appropriate. During these processes it is worth checking the body fixings are holding the body parallel to the rails and not twisting the frames.

 

Then start adding details.

Less chance of damage whilst fettling any of the above.

[Jol Wilkinson]

9 hours ago, jimwal said:

Get the chassis up and running with motor, gears and pick-ups. Coupling rods, cylinders, slidebars connecting rods and valve gear if appropriate. During these processes it is worth checking the body fixings are holding the body parallel to the rails and not twisting the frames.

 

Then start adding details.

Less chance of damage whilst fettling any of the above.

I find it is best to fix only one body retainer tightly, leaving the other very slightly "loose". That way the invariably torsionally rigid body assembly doesn't twist the frames.

[gr.king]

An alternative to leaving the second screw slightly loose would be to arrange things so that the second screw goes into a blind hole, and so that the screw is just slightly too long to be able to nip the body and chassis together when fully tightened. The screw could then be tightened, minimising the chance that it will progressively unwind and then fall out due to vibration when the loco is running, or being transported to/from shows.

[richard i]

3 hours ago, gr.king said:

minimising the chance that it will progressively unwind and then fall out due to vibration when the loco is running, or being transported to/from shows.

Speaking from experience I assume?

 

thanks one and all for the advice. 
richard 

[ian@stenochs]

15 hours ago, richard i said:

A big step. Major components fitted together.

Now whispering it quietly I think it has all been designed for p4. It has needed fettling to get this far and it looks like it needs some space made around the bogie wheels on the frame. 
decision time, cylinders or the small items on the body next?

 

it certainly now feels like this loco will get finished. Something I have not always thought.

richard 

no need to discuss the light reading behind. An occupational hazard/ necessity.

Better to scale down from full size and then make compromises for the model gauge rather than the other way round!   
 

Ian,

[Caley Jim]

Many years ago I was recommended to only use one screw to fix loco bodies to chassis.  That way there's no chance of causing torsion.  As long as the fixing point is a little way in from the end it will sit OK.  If need be, at the other end have some 'guides' either side of the chassis to centralise the body.  Where you are employing split frame collection, these need to be styrene, or other non-conducting material.

 

Jim

[gr.king]

21 hours ago, richard i said:

Speaking from experience I assume?

 

thanks one and all for the advice. 
richard 

I'm no stranger to finding that loose screws eventually fall out.

16 hours ago, Caley Jim said:

Many years ago I was recommended to only use one screw to fix loco bodies to chassis.  That way there's no chance of causing torsion.  As long as the fixing point is a little way in from the end it will sit OK.  If need be, at the other end have some 'guides' either side of the chassis to centralise the body.  Where you are employing split frame collection, these need to be styrene, or other non-conducting material.

 

Jim

Yet another option is to arrange for one end of the chassis to simply slot into some sort of slightly larger recess or loop under / within the body, much like the traditional Triang/Hornby arrangement. That end of the chassis is then held central and prevented from flopping down, without being gripped tightly to the body.