sen2two

one question im not to sure about...



i know when you balance pistons, they have them balanced to each other within a certain weight. so it dosnt really matter wich piston goes where in the firing order.



now, there are matching front a rear rotor weights. but if you get them balanced, does it matter if you switch up the front rear rotors???

RE_TurboFB

What would be the best place to get your engine balanced..??? I dont live to for from atkins rotary and I hear they do a good job..

I know racing beat will do it for $350 plus shipping, And (IMO) they know their **** about rotary's..

RX7 13B 4 UR AZZ

Use BDC im convinced in his work I cant say from experience because i have not used him yet LOL but im going to have him do my port work for my re motor. anyone who can do port work like him is an artist so he must do all his work good

BridgeportTurbo

I too am very interested in this question as i am using my existing turbo2 matched set shaft and rotors but had them machined for 3 mm seals and since then do not know which is front and rear or if it matters at all. does it?

BDC

Front and rear rotors doesn't matter since they're the same weight and have the same job. The only difference is which will wind up being labeled as Front and Rear in regards to the oil control ring springs during assembly day.



B

j9fd3s

ideally if you're reusing the rotor bearings and e shaft, you want to put the bearings back where they came from. in preactise it doesnt seem to matter much, and if you're replacing bearings it doesnt matter at all

j9fd3s

i sent my 12A to AZ rotary rockets, glen works for pual yaw, and is very thorough. i've known both tom and glen for a while too.

7045jc

I used Graham Wilkins Engineering in Seven Hills NSW

He has been building engines for years

I know he must be good because people are sending there rotary balancing from Victoria, QLD and even WA

His number is 02 96747037 or www.wilkinsengineering.com.au

Lynn E. Hanover

If those rotors were from the same engine new, then forget it. If you had to find a counter weight to replace a stock flywheel, then get it balanced.



The rotors will be within 2 alfas in stock trim. Close enough. The rotors are very heavy. Over 9 pounds each. So a few grams more or less is not a factor.



For example, suppose we have two flywheels and one flywheel weighs 10,000 pounds, is 10 feet in diameter and is out of balance a full pound and that pound is at the very outer diameter. Both flywheels turn 1000 RPM.



The second flywheel is the same size and turns the same speed, but weighs only 5 pounds and is also one pound out of balance at the outer edge. Which flywheel will you notice being out of balance? And why?



The second flywheel will cause you to flee the dyno room, as it tries to pull the dyno out of the floor.



You would probably be able to tell there was a problem with the first flywheel, but maybe not.



The balance error in the first flywheel is such a small percentage of its total weight, that it might go unnoticed.



Not the case with the second flywheel where the imbalance is a large percentage of its total weight.



In the rotary, with its heavy rotors, there can be a bit larger error in balance than say if the rotors weighed 2 pounds each.



Or, if the rotors had been extensively lightened.



Also, the rotors are just about filled with oil during operation. Under braking, the front rotor might contain just a bit more oil than the rear. When accellerating, the rear rotor might contain just a bit more oil than the front rotor.





As the engine runs, the oil picks up air and becomes foamed, so the weight of the oil is less as the engine runs.



So during operation, the engine passes back and fourth through the ideal balance, so long as the rotors start out reasonably close in weight. And that is what Mazda does.



Get them close.



I made up a balance beam scale out of an 8 foot 2 X 4. Two drywall screws through the center line. Two punch marks on a jack stand, and two hooks bent up out of lengths of 3/8 round rod from Lowes. You can bias the beam with a penny taped

along the top. A washer with a punch mark is screwed on at each end of the board. You keep reversing the hooks to be sure that they weight the same. Once you have it dialed in, a penny added to either end will show up dramatically. I think a penny is about 3 grams, so you can get real close with this home made scale.



I can do a drawing if anyone wants one.



Just clean up the rotors and dry them. Hang them in the hooks. Mark the heavy rotor. Reverse the rotors to be sure the heavy rotor is also heavy when on the other end of the scale.



Add 1/4" washers to the light rotor, until a balance is achieved. Reverse and check again.



The stack of washers gives you an idea of how much mass must be removed from the heavy rotor.



Use a very short 1/4" drill bit in a press. Adjust the positive stop to limit drilling to about 1/16". (about the thickness of one washer). Support the corner of the rotor with a shim or it will rock about on the land area. Drill a single hole on each corner of one side, along side of the factory balance holes. Not in one. If it appears that you will need less than three, make the holes shallower. If more than three, flip the rotor and drill some on the opposite side. Blow off all of the chips (wearing eye protection) and weigh again.



If you get it close on an 8 foot balance beam, it will be as good or better than Mazda did it.



If the counter weights came with this engine, just stick them back in. The rocking couple being out of spec a bit is nothing compared to the rotors being off weight.



Lynn E. Hanover



16X rotor on the left. 12A width but bigger diameter and more stroke.