Another use for solder

ard126k · Post by **ard126k** » Sat Nov 17, 2018 10:07 am

Last night in the 'social centre' the discussion turned to gear backlash and methods of measuring it. A former mechanic said that he used to do it by sticking a piece of solder wire between the teeth and turning the gears. The solder pushed the teeth apart and then got squashed between them. Turning the gears the opposite way released the solder which could then be measured to give the backlash. Same idea as Plastigage but cheaper if you have some solder lying about.

Anyone heard of this trick of the trade?

Alex.

Post by **Oldconn** » Sat Nov 17, 2018 10:29 am

That sounds good to me!

Post by **b.c.flat hat** » Sat Nov 17, 2018 12:45 pm

Hi Alex, it's definitely very "old school" but works. I've used it to equalise weights on the axles of steam locos, cut 1" wide pieces of lead, put them in front of all the wheels and run the loco over them. Mic the thickness and adjust the spring hangers. Repeat until the thickness is about equal or indicates that the correct ratio of tonnage is on the appropriate wheels. Simples

Post by **Will Yarrow** » Sat Nov 17, 2018 12:50 pm

I use this all the time for checking the squish on cylinder heads and anything you can't get a feeler gauge into, cheap and accurate.

Post by **Roger Pennington** » Sun Nov 18, 2018 2:23 pm

It's definitely a good idea, however, strictly speaking it's not quite the same as plastiguage. This works in a different way - it comes in the form of a fine plastic rod, which is available in a number of different, very precisely calibrated, sizes. If you want to measure, for example, a bearing clearance, you select the appropriate size of rod (to suit the clearance you want to measure), place a length across the bearing, and torque it up. When you undo it again, the rod will have been squashed, and will have spread to a particular *width*. Because the diameter of the rod was precisely known in the beginning, the width to which it spreads has a precise relationship to the clearance. So by comparing the width of the squashed plastguage to a scale on the packet, you can read off the clearance, without having to measure very tiny amounts, with greater possibility of error.