To fix the wobbly linespacing of the Hammond Multiplex typewriter, the rear-roller was covered with a single layer of heat-shrink tubing. The rubber of the rollers on most Hammond machines has aged badly, usually cracked from shrinkage. When acquired 2 years ago, the roller looked pretty bad.
It had already been sanded to make its surface even. Now also one length of 25mm (shrunk) diameter polyolefin tube was fitted over the old rubber. This worked to increase the diameter of the rear feed-roller and hide all the cracks.
With a clean, new roller-surface. The excess bits were cut off with a scalpel.
Whilst it is indeed possible to remove the rear-roller without taking the whole carriage apart, it is not recommended. Mr Hammond could certainly have made this a lot less difficult. It may be just this particular machine or it is the effect of accumulated design-changes that obscured the original design-intent. The tolerances are almost-but-not-quite-enough for cleanly taking out the roller. If only three parts would've been made about a mm shorter, it would've worked without issues. The parts being as they are, means that the erasing-plate even needs to be loosened to give the side-frames a way to flex (!) a little bit. These side-frames are delicate castings, that makes removal of the roller a risky undertaking. Fortunately it all went well and no broken casting - but removing the rear-roller still not a recommended thing to do.
The adjustments after re-fitting are also an interesting look into 1880s engineering - not before on a typewriter had I seen the need to adjust the linespacing detent to match the position of the linespacing ratchet. And there's so much more to adjust!
Result of it all is a Multiplex with a very firm grip on the paper and spacing lines as it should :-)
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