Bachmann B1

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barhamd
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Re: Bachmann B1

Postby barhamd » Thu May 14, 2020 10:15 pm

Thanks to Wizard of the Moor and a mail from Dave Bradwell I think I have worked out that the part 59 in the instructions actually refers to part 109 on the etch (described as the drain cock linkage). Dave suggests I don't actually fit this until later so the next task is the drop link.

I've been searching for some pictures which show 61046 in more detail/clearer than the two pictures I have at Clare from Transport Treasury but had no luck yet. I have a photo of 61048 in Cambridge next to a Class 31 which has the the earlier linkage. I'm not sure if any of the detail in Yeadons helps me.

I think that unless I can find out more I'll have to default to the earlier linkage.

David

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barhamd
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Re: Bachmann B1

Postby barhamd » Mon May 18, 2020 6:29 pm

So over the weekend I made some pretty good progress on the B1 chassis.

I managed to make up the drop links, complete with their little tiny oil fillers and fit them to the cross heads. These really were small but went on well, fastened with the rivet for the connecting rods. The cast piston valve ends were cleaned up soldered on without issue. I was then finally able to fasten the slide bars on and finally fix the clearances between the rods.

I was expecting the cylinder wrappers to be difficult but actually they curved up and soldered on quite easily. I just have the cylinder covers left to put on.

IMG_7991a.jpg


IMG_7992a.jpg


Thanks to Dave Bradwell for his support thus far, I'll remind him of his words 'the valve gear is actually straightforward...' when I ask more damn fool questions later..

IMG_7993a.jpg


IMG_7994a.jpg


I need to adjust the height of the front end. I think the springing on the bogie is currently too firm. Obviously at the moment there is no weight in the front end at all. I am getting a good few hours 'play value' out of this kit and very much enjoying it so far.

David

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PeteT
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Re: Bachmann B1

Postby PeteT » Mon May 18, 2020 8:06 pm

barhamd wrote:I am getting a good few hours 'play value' out of this kit and very much enjoying it so far.


Looking good! I can very much appreciate what you're saying here (from the J39), not the quickest - but it is all there and designed to go together, and an enjoyable journey.

Julian Roberts
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Re: Bachmann B1

Postby Julian Roberts » Mon May 18, 2020 8:29 pm

I think the springing on the bogie is currently too firm. Obviously at the moment there is no weight in the front end at all.

Could I suggest you get the weight in before adjusting the springing? My 2-6-0 experience suggests plenty of weight on carrying wheels is needed for reliable track holding. Great to read of your progress.

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barhamd
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Re: Bachmann B1

Postby barhamd » Mon May 18, 2020 8:47 pm

Julian Roberts wrote:
I think the springing on the bogie is currently too firm. Obviously at the moment there is no weight in the front end at all.

Could I suggest you get the weight in before adjusting the springing? My 2-6-0 experience suggests plenty of weight on carrying wheels is needed for reliable track holding. Great to read of your progress.


Yep, I think that is the best plan. I actually purchased a set of tiny electronic scales (as favoured by your local drug dealer :? ) onto which I built a track which would allow the weight of a single wheel to be weighed individually. I first used this on my J39 as it allowed me to get the weight on each wheel similar, particularly left and right sides.
David

davebradwell
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Re: Bachmann B1

Postby davebradwell » Mon May 18, 2020 9:27 pm

So you can start to think about weight distribution, assume the whole bogie will carry the same weight as a coupled axle. The loco should then balance initially around mid way between the front 2 coupled axles so you might find a handy lump of lead that will help testing. It's worth reflecting that twiddling the spring adjusting screws might change the distribution of weight but doesn't move the centre of gravity.

You'll probably find eventually that the bogie is well behaved without carrying much weight, unlike pony trucks which seem more troublesome.

Not much you can do to avoid the valvegear now!

DaveB

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barhamd
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Re: Bachmann B1

Postby barhamd » Mon May 18, 2020 10:07 pm

I'm just reading at this point, but slightly confused by the etching for the radius rods. I'm thinking I might be having to drill a hole that didn't get etched through but wanted to check.

IMG_7999a.jpg


IMG_8000a.jpg


Or does the hole which ends up in the middle of the expansion link get drilled afterwards?
Also I can see that there is a considerably different size between the holes in the radius rods (part 25) and the overlays (part 24). I'm presuming these need to get opened out on the overlay (which will be a fun job).


Thanks
David

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Will L
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Re: Bachmann B1

Postby Will L » Mon May 18, 2020 10:25 pm

barhamd wrote:...I actually purchased a set of tiny electronic scales (as favoured by your local drug dealer :? ) onto which I built a track which would allow the weight of a single wheel to be weighed individually. ...

Getting a weigh bridge to accurately weigh individual wheels/axles one at a time is notoriously difficult. I know Don Roland tried and failed as part of the Vice Chairman's Cup loco performance competition that used to be so much fun at Scaleforum years ago. I too have a modern strain gauge based scale and I've had ideas as to how it might be done but I haven't actually tried to put them into action.

Of course the proof is in the measuring. If you weigh each wheel/axle and add them together, how close does the total come to the real loco weight? Nowhere near was the answer for Don but I don't think he had the help of the sort of strain gauges available today. I'd be interested how close you got and how you did it.

Edited for spelling, we are getting our competitions and our compensations confused
Last edited by Will L on Tue May 19, 2020 12:37 pm, edited 1 time in total.

davebradwell
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Re: Bachmann B1

Postby davebradwell » Tue May 19, 2020 8:08 am

Yes, the pip on the overlay 26 should be a hole - it will be on the other side.

The hole in the middle of 24 is the pivot for the expansion link to rock. The hole in 26 is for a pin that goes through the slot in the centre layer of 24. They are different sizes.

DaveB

Julian Roberts
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Re: Bachmann B1

Postby Julian Roberts » Tue May 19, 2020 11:17 am

Yes - scales to weigh individual wheel weight is very interesting if they work, and particularly for me with my weird compensation ideas - but (and please excuse me for butting in again!) I personally would conclusively prove the loco fully works properly on all my track (once it's operational with rolling chassis and at least one pair of pickups), weighted as if complete, before going on to the fun stuff. But anyway you're obviously doing such wonderful stuff you can do without idiotic suggestions from me! :thumb

Dave Holt
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Re: Bachmann B1

Postby Dave Holt » Tue May 19, 2020 7:12 pm

It's not just model scales that have accuracy/repeatability issues! The railway where our loco is based has installed a set of load cells under short lengths of rail for axle load checking. I get the impression that every time a loco is pulled/pushed over, you get a different reading for every wheel, even when no adjustments have been made and the total weight doesn't always add up to the same, nor concur with the weight diagram.
Dave.

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barhamd
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Re: Bachmann B1

Postby barhamd » Tue May 19, 2020 10:29 pm

I would not try to say my weighbridge is particularly accurate in terms of absolutes but where it did come in use was getting a feel for which axles were taking most load.

IMG_8001a.jpg


I just put a load of lead in the body of the B1 and came up with the following, these are not final figures just an example...

Total loco appeared to weight 230g

weighing each wheel at a time (and I know this doesn't add up to 230) gives

from front to back

Left right
15g 15g
10g 20g
30g 60g
14g 16g
40g 20g

As I said I don't think this is worth much in terms of absolutes because the numbers are not stable enough but I think it is useful in terms of relatives. What I feel I could learn from this is that I have adjusted the grub screw too low on the right front driver and too low on the rear left. I'm slightly surprised by the difference on the bogie though, one rear wheel is reporting twice the weight of the other but that might be being impacted by the off balance leading axle behind it.

So I'll make a few adjustments and see how the numbers change and if the track holding changes at all.

One of the reasons I have not done a great deal of running with the chassis yet is that I didn't have a decent analogue controller. I didn't want to chip the loco until I had the running sorted out. I've got a controller on order which will hopeful arrive tomorrow and I'll be able to actually try and drive the loco around Clare and sort out any weight and balance issues.

I'll let you know how I get on.

David

Dave Holt
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Re: Bachmann B1

Postby Dave Holt » Wed May 20, 2020 9:31 am

David.
I think it's probably more important to try to even out weights across each axle than to get the ideal front to back values, although, for traction reasons, you want a sensible range between bogie and driving axles.
I suggest you make very small adjustments to the grub screws because, as you suspect, a change in one place will affect all the others. If it's anything like the full size, it will be a slow, repetitive process to get the result you want, but worth the effort.
Dave.

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Will L
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Re: Bachmann B1

Postby Will L » Wed May 20, 2020 9:43 am

barhamd wrote:I would not try to say my weighbridge is particularly accurate in terms of absolutes but where it did come in use was getting a feel for which axles were taking most load...


Thanks for that. I think it is a pretty creditable effort and the error (+10 gm or 4.3% over) is well within acceptable limits for most purposes. The scientist within me does wonder how repeatable the answers were but... So long as they are repeatedly consistent, that certainly gives you an useful basis on which to set up individually adjustable springs.

The difficulty when dealing with any sprung chassis is that quite small changes in the defection of a spring are significant in the degree they affect the weight being carried. If you're weighing a single wheel/axle and the weigh bridge deflects at all then you can start getting silly answers, which was what underlay Don's problem all those year ago. I can see it is defiantly worth while having a go at this now.

I suspect it may be the camera angle but the picture looks as if the rail bed either side isn't entirely flat, which could also affect the results.... but I may be getting a bit picky now.

nberrington
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Re: Bachmann B1

Postby nberrington » Wed May 20, 2020 10:50 am

barhamd wrote:I would not try to say my weighbridge is particularly accurate in terms of absolutes but where it did come in use was getting a feel for which axles were taking most ....

That’s a nifty weighbridge. Is there a detailed description somewhere?

Winander
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Re: Bachmann B1

Postby Winander » Wed May 20, 2020 10:53 am

Barry Luck used a similar system documented on is website http://www.lbscrmodels.co.uk/weight%20distribution.html
Richard Hodgson

davebradwell
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Re: Bachmann B1

Postby davebradwell » Wed May 20, 2020 1:32 pm

A good way to start spring setting is by turning the model upside-down and adjusting the springs until all axleboxes are sitting at the same rest height. The axle with the motor won't comply, of course, but at least it can be set level. Yes, this should be in the instructions. This gets you pretty close for starters. I then do a rough check with the model on a flat surface by going round each wheel and lifting it a little with a screwdriver, mainly to test for any sticking axleboxes but it also reveals any extreme light/heavy loadings. Measurements of footplate height front/rear enable the thing to be levelled and a square put against the cab side reveals any lean.

After that running trials may result in adjustments to weight on bogie and tender first running round curves is a good test for weight distribution.

Regarding weighbridges, going back a while there was the Deputy Chairman's Cup competition and which was taken over by one of the Scottish groups. They built or improved a weighbridge and did have considerable trouble getting reliable results. It was all written up somewhere, perhaps one of our archive specialists might know where. I recall they had to average several sets of readings.

DaveB

Paul Hutfield
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Re: Bachmann B1

Postby Paul Hutfield » Thu May 21, 2020 11:51 am

Thanks Dave, some very helpful/useful advice there and not just to B1 builders! A consistent starting point for setting the axleboxes prior to adjustment is certainly key in my mind before going any further. Assuming all the top of the horn guides are consistent across the driving wheels, it may well be worth making a gauge of some sort that can be placed between horn block and horn guide to assist with this process, doesn't have to be anything fancy. Looking at David's initial results, it does look read like the loco is not just nose heavy, but leaning to one side too.

I've spent many years in the model engineering hobby and attended and competed in a miniature locomotive efficiency competition called IMLEC on several occasions. One feature of this competition on occasions has been the ability to record axle weights, weighing each axle individually on a floating bit of rail, acting on a set of scales. I've always questioned the accuracy of this method wondering about the deflection of weight across the remaining axles with direct force on the fixed rail. In my mind, the truly accurate solution is to weigh all axles/wheels individually at the same time, just like they do on the full size stuff. A bit OTT for P4 of course ;)

Dave, I've sent you a PM but not sure if it's made it to you? Still showing in my outbox. Let me know if you haven't received anything. (Apologies for the slight diversion David)

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barhamd
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Re: Bachmann B1

Postby barhamd » Fri May 29, 2020 11:33 pm

I've not done much over the last week as I've been driven mad by builders doing 12 hour days on the house next door for 13 days straight. It seems they have to drill large holes in concrete once ever 2 minutes all the way through lock down.

Anyway I finally managed to get a few moments peace this evening and assemble the expansion links. I'd had to do a lot of work to shape these as the half etched sides were particularly under etched. Expanding the curved hole with a piecing saw to something which matched the inner, full etched part. The whole unit is pinned together with .35mm wire and consists of 11 parts.

IMG_8005a.jpg


I managed to get the pair made up and soldered without the inserted radius rods coming apart.

IMG_8006a.jpg


The radius rods are quite a tight fit around the expansion link and I am unsure how much rotation there is meant to be. It might be that the expansion link needs further thinning down to increase the angle the radius rod and rotate through? Trying to hold the expansion link at the same angle allows the radius rod to rotate between the two pencil marks below.

IMG_8007a.jpg


IMG_8008a.jpg


Putting the expansion links onto the motion bracket shows a few issues. On the left hand side of the locomotive the end of the radius rod seems to line up pretty well with the valve spindle, but on the right hand side things are way out and it is nowhere close. I'm not quite sure where the problem lies, the motion bracket is an extremely tight fit on the over the frames.

IMG_8009a.jpg


I think I have a bit more fettling to do, at least the expansion links clear the other rods and the wheels still go around.

David

davebradwell
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Re: Bachmann B1

Postby davebradwell » Sat May 30, 2020 8:44 am

You've done a lot of extra work there - the slots in the outer layers of the expansion link are purely cosmetic and much smaller than you've ended up with - the real slot on the prototype is only in the centre layer and the pin doesn't extend into the outers - note 'flush" instruction on diagram. Your arrangement wouldn't allow the engine to reverse as the dieblock can't go past the centre pivot. See prototype photos.

As for alignment, it looks as if during assembly of your motion brkt the wires through the frames have been distorted - try putting them in place again and see if a straight piece of wire will fit undeformed. This will have resulted in misaligned brackets. There are diagrams in the instructions showing the motion at the extremes of movement and as you assemble the parts check that they can move to these positions. If you're finding them a bit small why not print yourself enlarged versions as this is very important information. Concerning the offset in the radius rod, check that the holes are still parallel and at right angles to the frames. A thick piercing saw blade is handy for cleaning out forks and certainly the radius rod/expansion link requires careful fettling - it might have been a good idea to check swing before soldering.

When you make the combination lever use a drill as a gauge to check the 0.7 offset and confirm sections each side of the joggle are parallel by laying a straightedge along the component. Again, getting the valve spindle and radius rod to clear when lever at extreme angles will probably require some careful work around the outside of these forks. You might have trouble with your radius rod forks as widths taper - look at the drawing - you'll need full width as far as the half etched section on the back of the rod. Same applies to eccentric rod.

Ah well, it'll get easier! The devil's in the detail.

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Horsetan
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Re: Bachmann B1

Postby Horsetan » Sat May 30, 2020 10:29 am

I think the point of underetching small parts like these is to provide the builder with enough safety margin to file down.
That would be an ecumenical matter.

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barhamd
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Re: Bachmann B1

Postby barhamd » Sat May 30, 2020 1:35 pm

Well I can see I royally c*£ked that up...

Now that I understand the diagram and the fact that the slots in the external sides were cosmetic has been pointed out I understand.

So the question I'm left with is do I take the expansion links apart again, fill and recut the slots smaller and try again or live with my mistake.

The prototype looks like this....

b12-valve-gear2.jpg
b12-valve-gear2.jpg (111.64 KiB) Viewed 1117 times


Mine look like this (now I've pushed the pin between the radius rod and the expansion link flush with the radius rod)

IMG_8010a.jpg


I'm tempted to leave accept it and keep going...

Wouldn't it be good if you could have a photograph of the appropriate level of detail showing the valve gear in anything other than neutral!

David

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barhamd
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Re: Bachmann B1

Postby barhamd » Sat May 30, 2020 6:00 pm

The next bit of confusion is with the eccentric rod.

The instructions say:- Similarly assemble the eccentric rod as the diagram adding the fork at the front and the overlay at the rear.

I can understand how the overlay at the rear fits, but don't quite understand how the front overlay should be folded and soldered to form the fork. I can see different ways it could be bent, most of them probably wrong.

IMG_8011a.jpg


The rod has a half-etched recess in the end and the diagram says you need .7mm clearance in the fork.

Any ideas?

thanks
David

davebradwell
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Re: Bachmann B1

Postby davebradwell » Sat May 30, 2020 7:02 pm

I think you'd best leave expansion link well alone, although you'll have to find enough clearance to allow it to rock with respect to the radius rod. A bit of rounding of the lump on the radius rod will tidy it up. It's a pretty standard link on LNER engines, in fact the motion is very similar on nearly all classes should you be looking for more pics. The exceptions are the Thomson Pacifics - look at A2/2 and A2/3 to see a horrible link to model with the lifting arms passing through another layer of it.

A further thought - did you assemble the link with the corner pins held vertically in a block? If not and it's skewed then this might be causing your misalignment.

I'm sorry the instructions haven't guided you properly but after a few comments hinting at earlier efforts being rather dictatorial I've gone for a softer tone more recently.
I did wonder if I had some spare bits but don't, I'm afraid.

Adding the eccentric rod, there's a diagram at the top, middle of the page. You have your block with a suitable bit of wire sticking up vertically like it says and you put the rod face down with the pin through the front half of the fork. Rear bit is the half etched piece nearby which you bend near the straight end and similarly put over the pin. This fork is actually 0.45 wide so that's a bad start but put a spacer in the fork and solder 2 bits of knuckle together after adjusting length of little bent bit. The radius rod diagram shows it bigger - it joins the main bit at a steep angle. Spacer can be a piece of scrap etch with a notch to clear the pin.

DaveB

Crepello
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Re: Bachmann B1

Postby Crepello » Sat May 30, 2020 8:29 pm

davebradwell wrote:The exceptions are the Thomson Pacifics - look at A2/2 and A2/3 to see a horrible link to model with the lifting arms passing through another layer of it.

So no chassis from you for the forthcoming Hornby ones then? ;)


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