Fantastic information. I didn't realize there were crank driven tachs. So now I'll be looking for a 4-5K mechanical tach and try and find the bits and pieces to attach it to the front of the crank. Very cool.
The drive with the bracket is attached to the crank through a short flex shaft. It needs the bracket to hold the angle housing in place. The drive with the through-bolt is not going to move because the the through-bolt is holding it to the front of the engine. If the cable wasn't hooked up, it would spin around with the crank. But if you attach the cable and make sure the cable doesn't have too much slack, the housing will ride just fine. The actual housing casting is probably very similar in both applications. The internals would differ, and there may be a different flange for bracketery (or no bracketry), but those are incidental. Grease them both VERY well.
This is a good price (currently $75) for this tach. And if a guy wanted a black face or a different RPM range, it could probably be rebuilt for $150-200. Overall a cheap way to get into a vintage tach. A fella can make his own bracket for the drive, and buy one of these: https://www.pegasusautoracing.com/productdetails.asp?RecID=254
There's a 2to1 right angle tach drive on E-Bay for 24.85. http://www.ebay.com/itm/JONES-MOTRO...-500-RATIO-HOTROD-RATROD-MARINE-/251007555072
I patterened my tach drive after the cast piece shown above. The right angle drives are on ebay quite often. i had to machine a new part (the black nut) that holds it to the angle drive. The crank nut was turned down and a piece of flexible shaft permanently mounted. The end of the shaft has the tang which engages in the angle drive. The crank nut now requires a deep socket to install, then the rest is screwed onto the front of the engine. Took quite a bit to get everything perfectly lined up, but it's working great. The panel is an early Chris Craft (SW made?) panel. The tach is counter clock rotating which looks kind of cool. SW made these tachs in all kinds of rpm ranges and both rotations. more pictures of the roadster http://www.jalopyjournal.com/forum/showthread.php?t=704312
alchemy & swissmike thanks for all the great useful information and links. Thanks to everyone else that has contributed to a not too often thought about item. It seems I can easily fab up a bracket to hold in place a readily available right angled tach drive adaptor onto the end of any crankshaft. That to me screams pre war. What really spins my crank (pun intended) is that early purpose built dry lakes style Rod, and a crank driven mechanical tach would really fit the bill.
A Boned, good luck on the crank drive, it will be one of those items that when seen will be a definitely cool factor. Add a 4-5 grand early tach and it definitely wll fit the pre-war era. Half the fun is the hunt.
Wanted to see if anybody knows if the Flathead crank bolt sizes are all the same? The crank drive I have is for a 59 ab. Will it fit in my 21 stud crank?
They are the same for 8BA and 59A and I am almost certain they are the same for the earlier ones as well.
Man, that is one of the nicest gauge panels I think I've ever seen, regardless of what vintage instruments have been installed. Wow. Gary
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