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Hello all,
A long long time ago in a far off land I was engaged in Her Majesty's
Service and was privileged to see the fine handiwork of the Royal
Electrical and Mechanical Engineers (REME). In our outfit we had
occasion to pull some civvy recruiting trailers and other non SMP
trailers, which meant trying to sign out one of the much used Transit
Vans which as they were multi seater units was a hassle. We got talking
to the REME gods one day and broached the subject over a glass of brain
lubricator and they said that this should be a non issue as they could
knock up an adapter in a jiffy, why hadn't we asked for one before?
At the time I thought it was a neat idea and we kept ours in then unit
stores and slapped it on as required. Now in my current life I am the
owner of an ex military Land Rover 110 with the same fine rotating
pintle hitch, which if you ask me is the cats ass of all hitches ,
because it can be locked or allowed to rotate freely, unlike most other
pintle hitches that I know off. I also use my 110 as my daily driver and
want to be able to tow civvy trailers but REFUSE to hack my truck around
and remove the pintle for any other half assed unit. So my grey cells
warmed and glowed recently and after a trip to the meditation room with
a paper and pencil I sketched out my design idea and have now made two
units.
My copy of the REME Gods unit is made up of two plates sandwiching the
hitch with a spacer in-between to stop crushing and to located the ball
hitch which passes through the centre and bolts to a captive nut welded
to the lower plate, as I can't find a ball with a long enough shank to
pass right through and have space left for the nut and spring washer.
The nut is welded on the upper side of the lower plate and intrudes into
the opening. On the lower side of the same plate a flat bar, I used 1" X
3/8" bar stock, is welded and mates into the lock tab for the jaw. This
now stops the jaw from rotating, and keeps the ball upper most.
If you unlock the pintle and rotate it anti clock wise by 90 degrees you
now are presented with a vertical opening. This and the fact that the
Brit pintle locks are the key to this unit. I made up two plates of mild
steel 3" X 3" X 1/4" thick with a 1" hole dead centre in each. I am
fortunate as the hole making is done by an Amada Vipros 358 Fabricator
in one punch in a nano second, I know it is sickening for the rest of
you guys to have to buy the drill bits and all that jazz or torch it an
grind the result. Expensive and messy.
Welded to the upper plate directly under the 1" diam hole is a piece of
1 1/2" square HSS (hollow structural steel) with a 3/16" wall. The
length of this piece plus the height of the nut on top of the lower
plate should be a tad less than the total width of the hitch, to ensure
a tight fit. You will have to very carefully grind a little of one ( or
more ) of the corners of the HSS to fit your hitch real tight. I have
tried mine on two other hitches and found that they are not too NASA
tolerances so your adapter will only fit yours exactly unless by fluke
another is the same.
I have used a pair of balls from Hidden Hitch in 1 7/8" and 2" for my
adapter, both are 3 3/16" long shanks. The threads between the two are
common. Who knows they may be an industry standard but it is of no
consequence to me. I use the spring washer provided on the top plate
under the shoulder for the ball, to stop this un-screwing under
vibration.
You will notice that using this adapter will slightly mark your hitch
but this will depend on the amount of free play you build in, grind a
little at a time on the tube and you will have a real snug fit in the
opening and a tight grip between the plates.
I am a welder and fabricator by trade and MIG welded mine, but stick
welding with 7018 electrodes would be a good alternate. DO NOT USE the
60 series of rods i.e. 6011 etc. I ground the nut surface to remove the
chrome plating and laid a nice hot weld around the entire circumference
with a good tie in at the end. The same goes for the 1 1/2" HSS to the
upper plate and the locking tab on the under side. If you don't know
what your doing get a pro to do it.
Because we get alot of our work zinc plated I had mine electro plated
with aprox a 2 thou build up which is actually real good because the
thread was a little sloppy before but now is nice and snug. You could
red oxide prime and paint yours. I hate seeing rusting steel.
I am making a few of these for some very close friends but other wise I
am not going into production as I can't stand the thought of what some
idiots who have no common sense will do with such a unit and then come
back with their lawyers in tow, you get the picture.
If you have any questions I would be happy to answer them but all advice
and this article comes with the DISCLAIMER that this is for information
purposes ONLY and you make one of these on your own initiative and your
own RISK and RESPONSIBILITY.
rgds
Robin Craig
This archive was generated by hypermail 2b29 : Tue Apr 04 2000 - 21:57:27 PDT