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Compressors for the ABC

Over the last couple of days, I've spent some productive time cleaning and renovating the two small 300 psi compressors I bought at Enstone. They are correct for my ex - Sunderland flying boat ABC MkII Auxiliary engine and the multitude of stamps and numbers hiding under the dirt confirms their origin as aeronautical.

Whilst both have the same configuration, one is un-named and the other is by British Thompson-Houston (BTH). Both of them have CX prefixes on their part numbers and this can help to identify the actual manufacturer - "FB" would have indicated Bristol Aero Engines for instance. Anyone recognise the code?

Naturally, they are extremely well made and the big end assembly is a curiously arranged affair that consists of a brass block which shuttles to and fro in a slide machined into the ali centre crankcase. The conn rod is pivoted in the top part of the block . A good deal of the load which would otherwise be borne by the mainshafts is absorbed by this sliding block's (relatively speaking) huge surface area. Thus, the crank has two quite spindly main shafts which are supported by light weight roller bearings located in the two crankcase side covers which are in turn rigidly supported by a deep spigot around the mating face. One main shaft protrudes through the cover and is driven via a spline.

It is an elegant and well thought out little device.

Cleaned and wire brushed with a brass cup brush, I painted them black with a cellulose gloss enamel and set them aside to dry. Tonight I'll try fitting them - which, at a cursory glance, looked to me like it might be easier said than done!

Regards,

Kim Siddorn

Reply to
J K Siddorn
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Well, that's about as successful a venture as I can remember in recent times!

Tonight, I dragged the ABC blinking into the light, removed the two blanking plates fitted to the ancillary gearbox and fitted the two compressors.

It really was more or less as easy as it sounds. I had to shorten four studs each side, rethread them and grind a flat on the bottom of the compressor on the starboard side as the fuel pump was a bit in the way, but that was about it. Only took me a couple of hours.

While I was about it, I fitted the two new shrouded spark plugs and leads I bought from Roland Craven months ago. Very fetching!

I've uploaded a photographic record of the work from the found state to fitted into my Webshots ABC engines album. Page three, look for "BTH compressor" and then they are all in sequence.

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Regards,

Kim Siddorn,

Reply to
J K Siddorn

Did you take a pic of the big end assy you describe?

Reply to
Nick H

No. I knew at the time someone would ask, but I was up to my ears in filth and couldn't be bothered to go and wash me hands in order to use the digital camera. ;o))

Regards,

Kim Siddorn,

Reply to
J K Siddorn

I'll just have to read your description a couple more times then, in the hope that it sinks into my poor mechanically challenged brain!

Reply to
Nick H

OK. Are we talking some sort of scotch yoke arrangement?

Reply to
Nick H

Thenks Kuim, yes I think it is a scotch yoke or some slight variant thereof, but there is no substitute for actually turning a mechansme over in ones hands and seeing qhat it does. I think it is an appreciation of this sort of thing which separates the enginemen fron=m the boys. It may not be pretty with lots of shiny whirly bits to impress at rallies, but the engineering is gorgeous.

BTW, blue hylomar really is the ne plus ultra of jointing compounds, hurah to R-R for inventing it!

Reply to
Nick H

Reminded of my duty, I removed one of the BTH compressors, opened it up and took several photos of the crank in different positions. These I've uploaded to Webshots with a whole crowd of new pictures of this interesting little engine, all of which are a LOT clearer than the chemical ones that preceded them!

I've also completely reorganised the order in which they are displayed and I hope it makes better sense now.

The compressor pics have a blue Hylomar -ed face, so are easy to spot.

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Regards,

Kim Siddorn, Regia Anglorum

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Reply to
J K Siddorn

I like Hylomar and the now almost solid paste I have in the torn open tube on the bench has been around for about thirty years, a trophy of war from my parts managing days at Rolls-Royce. Not just nicked from the stores, but a pressy from the Rolls-Royce Cars warranty dept when I expressed doubts about its efficacy!

I responded that I thought their cars were no better than Jaguars, but it didn't work and I still don't have one!

The thin layer around the face was achieved by applying a "wedge" of paste into the angle of the locating spigot and doing up the nuts evenly. Good machining!

Regards,

Kim Siddorn,

Reply to
J K Siddorn

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