Another Pony to attempt repair of the Pony

It was local pick-up, but last year's purchase of a Marchant Pony B Special was a mistake. Had already seen on the listing that the machine in cosmetic bad shape (fixable), but had not realised quite how many parts were missing. Too many parts to be recoverable, so first put away in a box.

Just recently however, luck would have it that another badly-damaged Pony B appeared for sale online! The bidding interest in this incomplete and blocked machine may have been puzzling, but it looked to contain just the bits needed to attempt a repair of my Pony number 70049, frame nr. A1007. (The actual meaning and reason for these extra numbers is another thing to be explored.)

So now here a team of Ponies:

The target machine (top in photo above) already partially dismantled and both carriage registers taken out. The bottom machine will be the donor - serial number unknown (no back-plate), but frame number 1828. This donor-machine is a regular Pony B; so no input control-registers as with a 'Special'. The frame and housing of both calculators is mostly identical; to convert a regular Pony to a Special would only (?) require adding the control-register sub-frame (mounting holes are present in the base) and changing the left side-frame and top-cover.

Comparing the two, there are several small design changes visible. The (overly-complex) carriage indexing mechanisms are e.g. subtly different between the two and the revolution-counter is different too. Many/most parts should however be identical (fingers crossed).

Surprisingly the carriages are not interchangeable. The carriage base-rail of one machine is about 0.3 mm wider than the other - carriage 1007 will only fit on machine base 1007 and carriage 1828 will only fit on base 1828. That might be from a small change in the design, but may also be simply variations in size of steel-strip used for the carriage-base. 

Given the overall character of the machine and its Oakland, CA manufacture it is hard to imagine that this would not be a tightly controlled dimension. Interestingly, though probably simply because it's not relevant at the stage drawn, the carriage-width is not a dimension shown in below part-drawing of the baseplate of a Pony A:

Similarly the carriage indexing/holding pawl looks filed to fit its carriage - and stamped.

So at least the carriage, base-casting  and indexing-pawl need to be matched with these assembler numbers, even the right side-wall of the 70049 machine is stamped 1007! 

The machine covers are then all stamped 49 - for machine 70049. 

Oddly, the carriage cover of the donor-machine has 1828 written (pencil?) on the inside - hard to make out, but it's there. That is odd; a snippet of the serial number is expected there.

Both machines how evidence of major, old repairs (and major mistreatment too). The crank-rest of 70049 shows for example an old repair, the casting fixed with brass (brazing?).

This casting had probably been broken by a major impact or fall, as also hinted at by the mangled crank-handle and a slightly bent main crank-shaft. Crank and shaft will be replaced by the straight specimens from the donor machine.

Another hint that this calculator really has seen mis-use; about half of the clearing-pins on the register shafts are 'new', so something caused all these original pins to be broken or needing replacement. Evidence that it was pretty bad is that the whole carriage is actually bent! See the offset against a straight steel ruler:

Now with an extra parts machine, a repair will be attempted of 70049. To start with, a full dis-assembly of the machine and cleaning of all the bits. One sub-assembly at a time, starting with all the carriage bits.

A full rebuild of one (hopefully) working machine from two damaged ones is admittedly a lot of effort for a Marchant Pony B Special. These Marchant Ponies are not that common overhere, but also not so rare that a decent sample couldn't be obtained in time. In this case it is now more about enjoying the puzzle and discovering the mechanism and design choices of Marchant in 1917.

Finding out how the first American manufacturer of Odhner-lineage pinwheel calculators evolved its design :-)