I bought a Miehle Dexter Twin screw supercharger at an auction around 20 years ago, it bolts up to a Chevy spreadbore 4 barrel intake. It is about twice as big and 5 times as heavy as the Whipple SC on my TBI 454. When I google it all I find is printing press info. Anyone know anything about these, or even better where I might get a pulley for it? Long shot I know, but worth a try.
Yeah,yeah, post pics. Feast your eyes on this. I set the Afb on just to give it some scale. Somebody somewhere must have heard of these, I just can't find them. Bottom
I have not heard of them in terms of making automotive superchargers...not that it's a gilt-edged guarantee, but I collect information & trivia about superchargers & have information about quite a few oddities & obscure brands. Judging by the location of the oil line & what appears to be a vent, and the fact that the back bearings are relatively small & have zerks....aaaand the appearance of the inlet & outlet....my guess is that it was made for industrial use and was backyard-adapted to a car. You should be able to simply pick a steel pulley with the appropriate shaft diameter & keyway... determine the pulley "diameter" & V-belt groove by first choosing a lower pulley for your intended engine (so's you can choose a drive ratio)...and have at it. I'd use a good steel pulley if you can find one...not a cast-iron one (unless you can keep the blower rpm reasonably low), & definitely not a zinc or aluminum pulley. I suspect by looking at it that you will have to extend the input shaft somehow, but the pictures could be deceiving as to the length of the blower. Double or even triple V-belts would help a good deal as well, if you can find a crank pulley that will allow them. Have to rig an idler, too. To be honest, I doubt you'll get much actual "boost", but done correctly it will look like a home-rigged blower setup from the later '50s, which is cool. Too much boost & the V-belts will slip anyway. The old Cragar V-belt drive used three V-belts.
Observing that the patent numbers are in the 2 1/2 million range should tell you that this is a very old design. Here is an excerpt from comments by Stuart Hilborn, the father of the latter day mechanical fuel injection systems.....he is reflecting on the 1964 or 1965 Indianapolis 500 race.... " The power of the new fuel injected Ford V -8 was substantially better than the Offenhauser, but I couldn't help but feel sorry that I was essentially putting Ford into the racing business and putting Meyer and Drake, the Offenhauser engine manufacturers, out of business. The Ford engine quickly became the dominant engine. In an effort to revive the Offy engine, Champion Spark Plug Company put together a supercharged version of the Offy using a GMC Roots type blower which was currently being used very successfully in drag racing. I supplied the fuel injector system for it, but I didn't really believe in the concept. The blower was large and bulky, but the main problem was that Roots blowers have no internal compression and suffer from poor efficiency, particularly when the supercharger pressure is high. The final result was more horsepower than the Ford, but not a lot. The centrifugal supercharger project that we had been testing on and off for about 10 years produced much more power but had poor reliability in the blower and the blower drive. Meyer and Drake, inspired by the reasonably good power of the Champion Spark Plug project, decided to do one themselves. They chose to use a Roots blower built by Miehle-Dexter, and asked me to make a fuel injector for it. I did so and was invited to come to the first dyno test to oversee the fuel injector. Upon arriving for the test I got my first look at the blower, and was shocked. It was a standard commercial blower with, of all things, die cast rotors. This was not racing quality equipment. The rotors, in particular, were suspect, running at the high pressure and high rpm necessary in racing. The test got underway and on the first run, at about 3/4 throttle there was a bang and a clank, and the engine spit both rotors right out onto the floor of the dyno room. They had broken up into pieces and came right out through the injector throats, ruining the throttle shaft and butterflies in the process. The project pretty much died right there. They talked about maybe having better quality rotors made, but I am not sure it was ever done." Author's Note: I'm pretty sure Mr. Hilborn was referencing the Meyer-Drake 183 cubic inch motor used in this test. The small size of the blower would have been about right for 3 litres. The size was correct, but the materials used were not up to the task.
That's just what I was thinking. I've been an industrial plant operator for over 20 years and have seen lots of industrial blowers. Definitely looks like an industrial unit. Some of the roots types even look exactly like small car units. Most are usually a constant low volume, when running at a high speed, attached to an constant speed electric motor. Due to the fact that it was probably designed for a high speed boost may be low at typical engine speeds. Definitely looks cool and you would be the only one around running one, if you can work out all the kinks.
I found a reference to the company making industrial twin-lobe compressors for gaseous helium. Appearance-wise, the tag looks Sixty-ish to me...also doesn't have a zip code on it, which isn't a dead-certain giveaway, but often means that it's late '60s or earlier. Cool piece, regardless. Probably weighs 50 lb. or more?
Thanks for the good information and tips. That is the first time I have seen a reference to one in print. Very cool to see. This thing weighs closer to 100 lbs. I was in a hurry before work when I took the pics this morning or I would have weighed it too. I took the box it was in down from an overhead shelf and it made me stagger back, even being ready for it.
The actual manufacture of the piece could have been anywhere from 1949 to the present, but the patent numbers on the plate run from 2,491,677 to 2,519,588 (or something close to that, hard to read). Referencing these patent numbers to years issued produces this information.... <TABLE style="BORDER-BOTTOM: 1px outset; TEXT-ALIGN: center; BORDER-LEFT: 1px outset; BORDER-TOP: 1px outset; BORDER-RIGHT: 1px outset" rules=all cellSpacing=0 summary="The following table displays the calendar year along with the first corresponding document number issued in each year for selected patent document types (utility, design, plant, and reissue patents and statutory invention registrations)" cellPadding=7 ;><TBODY><TR><TD>1949</TD><TD style="TEXT-ALIGN: right">2457797</TD><TD>D152235 </TD><TD>PP00818 </TD><TD>RE23068 </TD><TD> </TD></TR><TR><TD>1950</TD><TD style="TEXT-ALIGN: right">2492944</TD><TD>D156686 </TD><TD>PP00911 </TD><TD>RE23186 </TD><TD> </TD></TR><TR><TD>1951</TD><TD style="TEXT-ALIGN: right">2536016</TD><TD>D161404 </TD><TD>PP01001 </TD><TD>RE23315 </TD></TR></TBODY></TABLE> So the DESIGN is at least 58 years old and like I said, the actual production of the piece could have been between 1949 and the present.
I weighed it before I put it away just now, 93.6 lbs. The word "Outlet" is cast on the housing on either side of the opening on top that the carburetor adapter is on. The bottom does not say "inlet". More fun and games.
Roots blowers push air between the rotor and the inside diameter of the case. The inter-meshing of the rotors in the middle keeps most of the backwash in check. Your blower will move air properly according to the outlet that is cast into the housing by rotating the driveshaft counter-clockwise as you view the shaft. With the outlet up, it would move air from the bottom to the top of the housing. By turning the driveshaft clockwise, the air flow would be reversed, moving from the outlet port in the top of the case to the inlet port in the bottom of the case. Question is, are the gears and bearings up to the change of direction? If the gears are spiral cut, the thrust will change. Is there provision for thrust in the opposite direction? Of course, if they're straight cut, there should be no difficulty.
darned if it doesnt look like the old blowers that were used on the old walk in refrigerators at an old hospital i used to work at years ago
in the HOT ROD YEARBOOK #5 ('66) they make reference to and show pics of the MIEHLE-DEXTER supercharger on the 168 offenhauser in the 1966 INDY 500. put out 17 lbs of boost underdriven .750. i believe i have a small 2 lobe of the same manufacture (see pic) but has no markings. weighs 40 lbs. there was another on the hamb w/ one that might be M-D on a flathead..search ...blower i.d or supercharger id....good luck
Hello Filthy McChevy, Just checking on how this blower situation turned out. I have a simular blower I would like to use and could use some parts. Did you keep this, get it running or gather any other information. Leave your phone number and I will call. Gary Gould
The Jalopy Journal
