by Vin Heron for webBikeWorld
Reading the webBikeWorld
technical article about fitting a tachometer to a Moto Guzzi ‘Jackal’
got the old brain cells whirring.
Since buying my Jackal I had really missed the benefits of a
tacho and as it was my first Guzzi, I could only go by the sound and feel of
the engine to tell me whether or not it was happy with the revs I was using
during changing up or down the box – I did not have a clue as to what those
revs actually were.
OK, I wasn’t doing clutchless racing changes all over the
place, and my lap times to the local bikers meet were not really a
consideration, but still, I was determined to fit a tachometer to see what
was going on in the noisy bit. I also really wanted an analogue clock
for use when touring (I was late a couple of times last year when touring in
the wilds of N.W. Scotland and missed a couple of closing times which led to
all sorts of grief) but that’s a different story.
After reading the article, I talked both to Martin at
Motoworks Pete
Morecambe at
Reboot Guzzi Spares to see what was available in the way of second-hand
tachometers. I also examined the drawings in the Guzzi manual.
I suppose I could have bought either a new or second-hand
Cali EV dash but they don’t seem to be all that easy to get hold of and I
had made up my mind to see what I could produce in the way of a new
dashboard myself (I am often accused of doing everything the hard way).
I also wanted to try and keep the horizontal layout of the original warning
light cluster, in preference to the Cali EV version.
The original Jackal item is stamped out of 4mm alloy plate
and the edge finish is pretty poor – surely I could improve on that at
least?
Well, in the end, it came out not too shabby and I’m quite
happy with it. The making of the thing was only the half of it
however; obtaining the right tachometer (I wanted one that matched the
speedometer), the cabling, the wiring loom etc were the other half and I
will tell you what I found out and the odd problems I encountered along the
way.
Materials
I could not determine what type of alloy was used by Moto Guzzi for the
original 4mm thick Jackal dashboard but experience told me that most
aluminium alloys would probably do the job by using a bit of care during
manufacture. As for stresses on the dash, these would be pretty
minimal.
For the technically-minded among you, the material I made
mine from was a bit of 4mm thick 1050-H14 aluminium (BS
1470). This is a 99.5% pure aluminium, which is malleable and has
good corrosion resistance. You can get a table, which will convert BS
(British Standards) to ASTM (American Society for Testing Materials) if you
need to.
Don’t worry if you do not have this material available; just
use what you can get. As long as you can pull a bend on the mounting
‘Lugs’ without it cracking, then it will probably be fine. Aluminium
comes in various grades of hardness: fully soft, half-hard and fully hard.
I don’t have a clue what grade the bit I got was. I just made a test
piece, put it in the vice, and it bent OK (fine, we’ll use that then).
Manufacturing Methods and Tools
This section may seem to be too early in the proceedings but how you intend
to manufacture the dash has a bearing on everything else.
Water Jet Cutting
I originally intended to have my dash cut out by the water jet cutting
process and found a local company that does it. As with anything,
start-up costs are the killer but this particular company makes aerospace
bits and is used to one-offs thus keeping it fairly economical.
Enough orders and it would be worth having a batch done.
I talked to the Managing Director about composite cutting
and PU / PE plastics and he showed me some samples that were beautifully
done with a splendid finish cut directly from CAD via Laser. Very
nice. This got me going I can tell you! Look for local firms -
it's amazing what you can find on your doorstep although it can be a bit
of a Sherlock Holmes job.
If you get stuck, take the original dash to the company
that does the water jetting and ask if they will use it as a template for
the warning light cluster holes PCD (Pitch Centre Diameter) and the
mounting holes and explain to them via a sketch what you want & where you
it. The company I spoke to were quite happy to produce a CAD
(Computer Aided Drafting) manufacturing drawings from my description.
Plasma Cutting
This is not a bad way to do it if you can’t be bothered to cut out the
profile yourself. Bear in mind though, that it will leave a
relatively rough edge which you will need to finish off yourself using
files, linisher, sander, flapwheels, whatever. You could extend the
process to cutting out the 85mm (diameter) holes for the instruments but
once again, you will need to finish the edges of the cut by hand and there
are much better ways of cutting these two large holes.
Laser Cutting
I looked at this method but rejected it in favour of water jet cutting.
This was only my personal preference and there is nothing that says you
can’t use it yourself.
CNC Milling
Possible and feasible if you own, or have access to the right bits of kit.
I don’t and haven’t so this one went out the window from the off.
Produce it Yourself
And who said today was going to be boring?
Tools
To cut it out yourself you need some basic hand tools and a
drill. If you have a small bandsaw, so much the better. If you don’t have a bandsaw, use a hacksaw but wear some
Wellies to catch the sweat.
I was given a little Black & Decker bandsaw which must be
about 300 years old. The blade is fairly coarse at 10 tpi (teeth per inch)
and I am sure it is a wood, rather than metal, cutting blade, however, I
took my time and didn’t force it when cutting out the profile, and it did
the job beautifully. A good tip here is to drill a hole at each corner
for
when a line changes direction; this will allow you to rotate the dash and
stop the blade snagging.
To cut the 85mm
diameter holes (or 3.346” in old money), go out &
buy a hole cutter if you don’t already have one.
The cutter I used is what I
have always known as a ‘trepanning’ tool – they call them ‘Tank Cutters’
nowadays in the UK (see photo left).
It is infinitely adjustable and can be used
for all sorts of other stuff. It cost about £8, so it won’t break the bank
and gives not a bad finish with a little tweaking here and there.
A hole saw
gives the best cut; however, I couldn’t get one anywhere in 85mm.
A couple of medium / fine flap wheels are needed, both for
finishing off the edges (although I used files and wet & dry paper) and for
doing the brushed satin finish.
A few files, a bit of wet & dry sandpaper, a couple of drills and a countersinker for the warning light cluster / mounting screw holes and
that’s about it really.
Manufacture
Drawings
I produced the drawing as I originally intended to use water
jet cutting. As it happens, it came in handy anyway. The only dimensions
that are fairly critical are the holes for the warning light cluster
(including the 3 x off countersunk holes for the screws that retain the
cluster to the dash). The remainder of the dimensions have some tolerance,
and you can make adjustments to the fit. The bend line also has a bit of
tolerance.
Handling The Material
You won’t get a good brushed finish if at the end of
machining / cutting out, your dash is covered in scratches, gouges and
dents. Aluminium normally comes with a translucent cling film type of
covering – remove it from one side and cover it with masking tape. This will
protect the finish and give you a good surface to do your marking-out on
with a very sharp pencil. You can centre-pop the holes through the masking
tape and you only need to totally remove it when you have finished the
machining / cutting out.
Marking Out
See the drawing for the dimensions. If you do not like the
shape, tweak it to suit yourself.
You have a couple of options here; either mark out the shape
on the masking tape using pencil, compass and scribers or print-out a full
size copy of the drawing and use it as a template to transfer the outline
shape to the plate.
Probably more accurate to mark out all the hole centres
onto the masking tape and then use a template to mark-out the outline.
You should be able to see the rolling direction of the
plate; make sure the ‘grain’ of your dash runs fore and aft as this will
help give you a better finish.
I used the original dash as a template and drew the whole
thing out on the piece of Aluminium. I then drew a horizontal line through
the hole centre and used this as the horizontal centre line for the twin
holes, spacing their vertical centre lines far enough apart to leave about
5/8” of material between them (at the centre).
I then drew a line parallel
with the circumference of these two holes, to allow about 5/16” of material
around the holes, and using a French curve, drew a smooth radius to blend
the lines into each other.
Cutting Out
The sequence I used to make it was as follows:
-
Mark out the plate, including profile and hole centres
-
Centre-pop all of the hole centres
-
When you have the hole centres marked-out, centre-pop
them using sharp centre-pop. A light tap should do it in a material as
soft as this - you don’t need / want them too deep.
-
Pilot drill each hole centre using something like a 1/16th
drill
-
Cut the 85mm holes
-
Use the trepanner / tank cutter or an 85mm hole saw if you
can get one.
-
Drill the warning light and mounting holes. De-burr.
I finished off the warning light holes in the top face of
the dash using a bit of wet & dry as I wanted a really clean edge to the
holes. For the underside of the dash, I just used a large drill, rotated by
hand. When you have completed this operation, do a trial fit of the warning
light cluster. I had to relieve one hole slightly with a round file to get
the warning light cluster to fit snugly but this only took a couple of light
strokes and in she went.
-
Cut out the profile using a hacksaw / bandsaw / plasma
cutter
-
I used the bandsaw and it gave a really good edge.
-
Smooth off and finish off the edges
-
File, wet & dry, wire wool, flap wheel can all be used to
remove cutting marks and give a nice, neat, smooth edge.
-
Bend the ‘mounting lugs’ to the correct angle using the
original dash as a pattern
Get two pieces of a hardish wood, such as Beech – make sure
they are smooth. Clamp the dash in a vice between the pieces of wood to
prevent marking the Aluminium with the vice jaws. Line it up for where you
want the bend to be using the original dash as a template, and bend to the
correct angle.
I placed a piece of wood behind the dash and gave it a whack
with a wooden mallet, checked it against the original dash, then gave it a
few more whacks until it was at the correct angle. Precision stuff really.
Surface Finish
When you have the ‘mounting lugs’ bent, finish off the dash
with a flap wheel. I used a flap wheel in a pistol drill set at drilling
speed (i.e.: not too fast) and didn’t apply too much pressure. Find a scrap
piece of Aluminium to practice on and you will soon get the idea.
As I was working on my own, I clamped the dash to a bench
(put wood under the clamp to prevent marking the Aluminium). Better to
press-gang a volunteer if you can.
Holding the drill with both hands, and starting at one side, I ran the flap
wheel down the dash in one smooth and even stroke. This will give you a
‘stripe’ of satin brushed finish. I repeated the strokes until I had
completed the surface finish.
There are other finishing options if you don’t fancy doing
it this way. Depending on what is available in your locality, paper
blasting, anodizing, etc. are all good methods of obtaining a professional
looking finish you can be proud of. I think a brushed finish, which is then
anodized would make a fine job and depending on the colour of your bike, you
could be really creative here.
Finishing-Off
Get some Methylated Spirit and de-grease the dash, trying
not to leave any finger marks which show up easily on Aluminium. Spray with a
few coats of acrylic lacquer.
I got a can from a car accessory shop which did the job
perfectly. I allowed the spray can to reach room temperature, warmed the
dash a little, then gave the edges only a couple of light coats.
When these
were dry (about 15 minutes) I then lay it flat and sprayed first one, then
the other, side of the dash with a few coats until I was happy with the
finish. I left it overnight before any subsequent handling, then gave it a
gentle ‘T’ Cut and wax.
Fitting and Connections
Cables
The speedo cable fits fine.
Wiring
The wBW article "Moto
Guzzi Jackal Tachometer Installation"
should give you plenty of information on how to wire things up.
In addition
to the instrument bulb holder, the rear of the tacho has 3 x off spade
terminals (see photo, left); a +ve, an earth and a spade marked ‘1’, this
latter being the connector for the feed from the ECU to power the tacho.
For instrument lights, I took a tapping from both the +ve
wire that powers the speedo instrument light and the -ve earth wire where
they connect to the speedo. That way, the joints are inside the speedo
cover.
I made up two wires; one with spades (+ve instrument lights) and one
with a ring terminal one end and a spade at the other (-ve instrument earth).
The other wiring you need is for the feed to the tacho
itself from the ECU. The jackal is pre-wired for a tacho as shown in the
circuit diagram in Section P, Page 16 of the Guzzi manual. (I assume this is
what ‘Predisp.’) means.
‘All’ you need to do then, is to find the “10-way A Pakard
connector (dashboard)” and trace the pre-wired socket. Easy, no?
Have a poke around the front of the bike (technically
speaking) when you have removed the old dash and you will find it.
