I've heard a bunch of different names for these, but I guess they're a tachometer cup? Tach holder, gauge mount, I don't know. But i made one because I bought this really sweeeeeet rediculous looking marine tach, while I was looking for a tach on ebay. It had a bunch of other stuff in a panel for $35, but this was the only piece I wanted. I tested it under hood with my timing light's tach, and it is pretty close reading to the light so I'm going to give it the OK on functionality.
Did I mention it also says CHRYSLER, and the number "6"? Yeah it's perfect. The marine word can stay for now, but I'll probably pop it apart and make it go away later.
The only problem is I did not have anything to put it in once I pulled it out of the rest of the cluster - SO I made something.
Materials I used:
ABS glue $6.00
1x 3" ABS cap $1.50
1x 3" ABS slip/slip joint $2.00
A 5" wide section of 3" (had some)
Some wire and wire shielding
Solder
Electrical tape
Tools:
Chop saw (could use a hacksaw?)
Soldering Iron
80gritt, 220, and 320 sandpaper
First, I took the cap, and used some 80gritt to take the raised lettering, numbers, and casting marks off.
After that, I smoothed it back out with some 220 and then 320.
I inserted the leftover 3" abs into the cap, and set it on the chop saw so I had something to clamp to when I cut the back half of the cap off - so it would shorten the overall assembly.
I cut a small portion of 3" ABS pipe off, and made a piece about 2" wide that tapered to 1".
This allowed one part to stick out, and the other to be flush mostly with the cap. It was hard to take a picture to display the shape. I glued it into the shortened cap using ABS glue.
I then drilled one 3/8" inch hole in 6oclock position of the cap, and a 3/8" hole in the 3oclock position, and a smaller 1/4" hole in the 9oclock. The 3 and 9 will allow me to put a screw into the 1/4" using a screwdriver inserted through the 3/8" hole to screw the assembly into a small hole in the A pillar of my car. I may add more holding power, but for now, getting it set up right and visibly will be key, then I can measure and make another mounting point.
I set the small cap assembly onto the 3" slip/slip joint. I did not glue this. Instead I drilled a small hole through the slip, and into the longer section of the 3" abs in the cap to attach the two pieces together. This holds it sturdily together, and will allow me to remove the cap and push the tach out, or deal with an electronic issue in the future easily.
There's a small ridge that stops the two sections of pipe you would join in the slip/slip joint. I used 80gritt and patiently sanded the ridge away till it was just right to slip the tach in tightly and not allow it to move.
I then started wiring the harness for the tach. I used a small 12v bulb I had to light the tach till I find a pig tail that will fit inside the hole in the tach and bulb. I made a small plastic holder with two wires that i wrapped in tape to keep the bulb from moving around. It's pretty stable. I rigged it all to the tach, along with the feed line that will go to the coil.
This is the harness complete and the bulb swapped over to the other ground post and it sets nicely in the lighting spot.
This shows the tach pushed into the slip joint, and how the assembly comes apart. The harness slips out through the 3/8" hole in the 6oclock position of the assembly.
The lip on the other side of the abs allows the tach to sink in before it sits flush, and you can not remove it unless you take the back off, and push the tach out from the back. It takes a lot of pressure to do so. I sanded the casting ridge off the slip joint, and smoothed the whole thing out with some 220 and then 320.
Here you can see the exit hole i will use to install the stealth screw in. This is what the finished assembly looks like, and tomorrow I will dissasemble it again and hit it with some nice satin black paint to finish it off - or maybe white. I haven't decided.
I've been using ABS to mount gauges in for a while in cars and other stuff. This is the biggest one I've made so far. Usually you just have to decide what part of the pipe you need. The pipe itself will be 3" inside, but the OD is 3 1/2" so the coupler will be 3 1/2" inside. This particular gauge was just shy of 3 1/2" diameter - so it needed to be mounted in the slip joint.
For the smaller 2 1/8" ones, I use the 2" PVC or abs slip joints. You need to make up about 1/8 or 1/16 of material, so I wrap the gauge in electrical tape in one stripe till it is just slightly larger than the slip, and then pack it into the slip. It will stay till you pull the back off, and push it out.
