It's been a long time since I used steemit and I wanted to update everyone on a project that will be starting but may take a few years to complete.
Introducing one of the rarest rotary engine parts on the market. The Mazda 13G triple rotor eccentric shaft. My plan will be to have the shaft fitted with Racing Beat Type 2 stationary gears and low compression rotors for a new heart in the rx7.
For those of you who do not know about the 20b rotary engine (or triple rotor) it is the jaw dropping, heart racing, barrel of angry bees that top tier enthusiasts drop in. While some four rotors are slowly entering the market the majority of rx7 drivers will only ever own a 13B twin rotor. The main reason is the substantial cost required to bring a three rotor onto the street compared to the average cost of the car itself. While FD RX7s are trending up in price the 20b center irons have doubled in recent years. Currently sitting at $4,471 USD used and $8,937 USD for new at Atkins Rotary in the states.
The build I am looking at is unique, and it starts with the eccentric shaft. The 13G shaft was engineered by Mazda Racing for the Le Mans car of the early 80s. There isn't a lot of information out there about it but what is available suggests its a promising collectors piece.
The 13G engine was produced around 1983/1984 for the 1984 LeMans 727c race car, and was used until about 1989.
The engine was based on the 13B engine of the time, with some special parts:
*Special centre housing with phasing gear
*Eccentric shaft to suit the 3 rotor design
*Different front housing (which has holes for the tension bolts to go through, as the tension bolts screw into the special centre housing).
*The rotor housings were the type with the water seal groove. (But, the external shape of the housings is narrower than the 13B)
*Most other parts, while virtually identical to the 13B, were custom-made for this engine
The eccentric shaft used was a new design not previously tried by Mazda. Previous designs were made from modified 2 rotor eccentric shafts joined together with bolts and keyways, which were not rigid enough for extended periods of reliable operation. (This claim I find hard to believe considering it was being used in a Le Mans 24h car.)
Essentially it was a 2 rotor shaft with a long extension on the front of it that went all the way to the front pulley. Then for the front rotor there is an eccentric shaft "sleeve" which slides over the front extension on the eccentric shaft until the angled section of the main eccentric shaft meets the corresponding section in the "sleeve" (Just like the flywheel does in any Mazda rotary).
The bearing/spacer/bolt down plate used to adjust the backlash (as in any Mazda rotary) performs the task of pushing the extension sleeve onto the tapered section.
The extension sleeve is indexed (so the rotor is in the correct phase with the other rotors) by a small keyway.
