Trailer Tongue Weight Scale

[Titaniumboy]

Here is an interesting little DIY project from back when Popular Mechanics magazine assumed many of their readers could operate a metal lathe. The article is from October 1978.

The cool part to me is that the cylinder bore diameter of 1.128” was not chosen at random. It turns out that a circle with a diameter of 1.128” has an area of almost exactly 1 square inch (within 0.07%).

https://books.google.com/books?id=4M4D ... e&q&f=true


The article is in error about the width of the two piston grooves. The grooves should be 0.180” wide instead of the 1/8” shown. The dimensions of the groove tool are correct. Another error in the article is that the aluminum rod for the piston should be 2-3/32” long instead of the 23/32” long as shown in the Materials List.

This next link is from January 1979 a couple months later and shows two Letters to the Editor regarding the trailer scale.

https://books.google.com/books?id=i88D ... e&q&f=true


Of course you could buy one already made from Sherline for about $157.

https://www.sherline.com/product/sherl ... escription

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[bruceb58]

I have the Sherline. It's awesome and inexpensive...no need to make one.

[DEcosse]

I got a cheap one from EBay
https://www.ebay.com/itm/192874481388

These are typically rated to be 3% (this particular one linked does not state)
But honestly, if it's even 10%, does it really matter?
I mean conversely, if scale was absolutely accurate and your measured weight was 50lb off the 'ideal' median, it's not like you would change your distibution for that, would you? (or would you?! )

It's something that is going to be used once and then sit in the garage, so personally, that's good enough for me.
It would be nice to otherwise support an American company, but with it's expected utilization it's hard (for me) to justify the cost differential.

p.s. I was actually surprised to see that Sherline does not appear to list an accuracy in their specs - I may have missed it, but I looked at both description and specs pages.

[bruceb58]

p.s. I was actually surprised to see that Sherline does not appear to list an accuracy in their specs - I may have missed it, but I looked at both description and specs pages.

As accurate as the gauge itself is. The bore is one square inch so its just supplying the oil under pressure to the gauge.

I actually use my Sherline fairly often as I change things on my travel trailer. On a boat trailer, it won't matter as much.

This is my R5 with very little fuel.

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