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  #41  
Old 01-06-2020, 03:41 PM
creosotewind creosotewind is offline
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What? No "Schweppes Lemon Squash"? (whatever that is)

But this whole thing looks great. And a great presentation as well.
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  #42  
Old 01-07-2020, 04:36 AM
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Quote:
Originally Posted by creosotewind View Post
What? No "Schweppes Lemon Squash"? (whatever that is)

But this whole thing looks great. And a great presentation as well.
"I believe it is a popular fruit drink, M'lud." I have no photographs of B340 carrying an advertisement for Schweppes, but I have no doubt that B-types did so from time to time in the 1910s and -20s. It is the LTM's preserved K-type K424 which appears to have one currently on its right-hand side. The ABC model (see my first post in this thread) shows it on both sides, but recent photos of the left-hand side of K424 show an advertisement for the Great Western Railway.

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Now for the mostly black chassis. The two faces of each long side are layered on thin cardboard - my stock is 0.65mm thick - then again on thin card or paper until the combined thickness of the two sides is 2mm. Then the ends and bottom receive a covering strip to hide the cardboard filling. The top does not need a cover, as it is glued to the floor plate.

London General B-type bus, 1:32-pic49.jpg London General B-type bus, 1:32-pic50.jpg London General B-type bus, 1:32-pic51.jpg

The prototype chassis is in fact wooden, sheathed in steel plate, so I claim that my design is very authentic... In fact, of course, it was just the easiest way of making a tidy, strong girder.

The cross pieces are similar, but lighter - 1.3mm thick.

London General B-type bus, 1:32-pic52.jpg

They can all go together. There is also a tie rod joining the front horns, which I just made flat, as it is too small to roll a cylinder.

London General B-type bus, 1:32-pic53.jpg
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  #43  
Old 01-09-2020, 03:06 AM
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Now for the drive train. There is the engine crankcase at the front, with a large exposed flywheel, the chain operated gearbox in the middle, and a worm driven rear axle. These are all only just visible from the side, so I have simplified them greatly. In the case of the gearbox and final drive, all that can be seen is a protective undertray, so I have just continued the profiles upwards as a block.

London General B-type bus, 1:32-pic54.jpg London General B-type bus, 1:32-pic55.jpg

The front two blocks can be glued to the chassis, whereas the final drive floats on top of the rear axle, so will await that.

London General B-type bus, 1:32-pic56.jpg

At this point I discovered that somehow I had managed to mirror the gearbox cover, so that the holes for the transmission shafts were in the wrong place. Back to the printer to fix that, and I'll take the opportunity to fix the colour of the lamp brackets and try to improve the bonnet handgrips.
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  #44  
Old 01-11-2020, 08:45 AM
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Fixing the gearbox cover was no problem.

London General B-type bus, 1:32-pic57.jpg

Nor was the recolouring of the lamp brackets. However, when I was thinking about the handholds I found a good nearly-side-on view of B340, and scaled it to sit underneath the part outlines. The proportions of the markings as taken from Mr. Rose's drawing were nowhere near the real ones. The straight sides were not tall enough so the curved top was too deep and curvy to make the overall height come out about right. In addition the fleet number plates were too small and the printed handholds too large and too close together. Of course I failed to resist redoing it all, but I did at least manage to make some plausible handholds

London General B-type bus, 1:32-pic58.jpg London General B-type bus, 1:32-pic59.jpg

A bit of a waste of time really, but I do think it looks better.

London General B-type bus, 1:32-pic60.jpg
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  #45  
Old 01-11-2020, 10:04 AM
rifleman rifleman is offline
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well to me its not a waste of time it really looks the part nice touch well done
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  #46  
Old 01-13-2020, 02:37 PM
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I think I have made a serious mistake... I have just obtained a second-hand copy of "AEC Vehicles: Origins to 1929" by Brian Thackray. It has many photographs and drawings of the early LGOC and AEC buses and lorries and a fascinating story of their development. I am going to have a great problem stopping myself redoing everything in the light of this new information.

London General B-type bus, 1:32-pic61.jpg London General B-type bus, 1:32-pic62.jpg

Apparently the reason General started designing its own buses in 1909 was that the Metropolitan Police, who were the licencing authority for all public passenger-carrying vehicles in London, chose to impose much stricter restrictions on London buses than the rules applying to the rest of the country. As a result the majority of the General fleet was non-compliant, and couldn't be replaced with standard products from other manufacturers. The regulations specified maximum length, width and wheelbase as well as unladen weight and gross axle loadings.

A further requirement was a very low level of noise in operation. This was unachievable with the normal straight-cut sliding mesh gears of the time, or even with a helical-cut constant-mesh box. As a last resort a large, heavy and expensive chain gearbox was chosen.


Image from the London Transport Museum web site.

In 1926 Frank Searle, the LGOC Chief Engineer and designer of the X-type and B-type, said "I am sorry to say that the X type soon proved to have rather serious defects", though sadly he did not expand on what they were. This is what led to the B-type.
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  #47  
Old 01-14-2020, 10:18 AM
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sharunas sharunas is offline
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Looks like predecessor of modern CVT gearbox.
Very interesting post.
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  #48  
Old 01-16-2020, 02:57 AM
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Quote:
Originally Posted by sharunas View Post
Looks like predecessor of modern CVT gearbox.
Very interesting post.
Indeed, though with internally toothed chains it was very definitely fixed-ratio.

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Back to construction, with the rear axle. A simple approximation to a sphere for the differential, a tube to contain the half-axles proper, and strengthening ribs and bar, all copied (by eye) from the Airfix model.

London General B-type bus, 1:32-pic63.jpg London General B-type bus, 1:32-pic64.jpg

It sits partly inside the final drive slab, suggesting where the worm drive belongs.

London General B-type bus, 1:32-pic65.jpg

This is upside down - once installed the worm drive sits on top rather than underneath.

Here I nearly succumbed to the temptation to redesign it, as the actual differential housing is more like a double cone with a narrow central cylinder, much as I have shown it, but with the axis parallel to the axle rather than fore-and-aft. Reason has prevailed, however, as it is quite well hidden on the final model and presents an acceptable shape should it be glimpsed.
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  #49  
Old 01-18-2020, 04:41 AM
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Now for the springs. These are made up of separate leaves, seven for the front springs and eight longer, wider and thicker ones for the rear.

London General B-type bus, 1:32-pic66.jpg

I first spot glued them at the centre, to get them aligned, then glued the remainder of the leaves and put them in a sliding former made from 1.5mm mounting board and let them dry under pressure.

London General B-type bus, 1:32-pic67.jpg London General B-type bus, 1:32-pic68.jpg

Then the same for the rear springs with another larger former.

London General B-type bus, 1:32-pic69.jpg

I haven't detailed the leaf clamps, as they are very small and mostly hidden - they are just narrow strips wound around the leaves to give an impression. The spring ends are hooked to fit the hangers and shackles by which they are supported.

London General B-type bus, 1:32-pic70.jpg
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  #50  
Old 01-20-2020, 03:02 PM
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Fitting the springs. The front spring is simple, being hung directly off the chassis rail. The front end fits directly into a U-shaped hanger, while the back connects to its hanger through a swinging shackle, which takes up the elongation of the spring as it is compressed.

London General B-type bus, 1:32-pic71.jpg London General B-type bus, 1:32-pic72.jpg London General B-type bus, 1:32-pic73.jpg

The rear springs are a bit more complicated. They are some distance outside the chassis frame, so the hangers have to be cantilevered out, and are a good deal more substantial.

London General B-type bus, 1:32-pic74.jpg

Again the rear hanger has a swinging shackle, though this time the lower end of the shackle is attached to the hanger, and the upper end to the spring (the reverse in the photos as the chassis is shown upside down).

London General B-type bus, 1:32-pic75.jpg London General B-type bus, 1:32-pic76.jpg
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