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10 Jan 1914. Saturday.

11/01/2014

Perhaps Frank had an early finish on the Friday, because he was in on the Saturday to finish off the details of the chassis.

Drawing 546 shows the bracket that fits on top of the crossmember at each end in order to complete the junction between it and the rear stanchions, and drawing 547 shows the axle.

546 Chassis Detail of Bracket B 10-1-14

547 Axle & Details 10-1-14

These are the last sketches of the chassis, so it might be worth going through the changes that were made later on in the production run.

After the first flight in March, the chassis was widened from 1250 to 1460mm track (you can see reference to this on sketch 547 where it gives the new length of the axle. They must presumably have altered the stanchions and crossmember, and quite likely the fittings too, but there’s no reference to these on the old drawings, or on later ones.)

Then in December 1914 when they got the first production order, they made a number of other changes. The crossmember was made solid from a single piece of spruce – possibly to save weight, but more likely, in my view, because the glue joint between the two halves would have been prone to coming apart in service. The rear stanchions were made in ash, not spruce. Ash, being a hardwood, is much heavier, but it’s better able to withstand compression loads, and the rear stanchions get LOTS of those! And all the stanchions and crossmember were wrapped in fabric to help protect them from stone damage.

I don’t know if they had a sudden drive to save weight, but a number of bits that were originally made of steel were altered to aluminium. These include the bracket in sketch 546, (which loses its web, since aluminium generally wasn’t welded in those days) the fittings at the top of the front stanchions (sketch 543) and the sleeves for the axle. These are areas we wouldn’t use aluminium today for sound engineering reasons, so 1246 has reverted to the original steel specification of the prototype!

One other change was made – probably at the transition from the C to the D in late 1915. If you look at the axle sketch (547) you can see at the top right a note with an asterisk referring to a steady cable. They are clearer in the photograph from the parts list below.

They went from the axle to the chassis foot on the opposite side, and were there to stop the axle from slipping sideways. It’s an odd system, and having fitted it on 1264, we are concerned that there’s nothing to stop the axle from rotating, and wrenching these cables as it does so. At some point (possibly on the D Scout upgrade) they added metal hoops to the chassis foot fittings which enabled the axle to slide up and down a limited amount, but stopped it moving sideways.

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