Engine Balancing

Rotary Engine Balance

With 20+ years of experience and a keen understanding of Rotary engineering, along with the aid of a Sunnen engine balancer and our milling center, REC has perfected the process of dynamic balancing of all Rotary engine rotating assemblies. Below are some balancing services we offer.

Rotating Assembly Balancing

Once the matching and balancing of a set of rotors is complete it becomes necessary to dynamically balance the entire rotating assembly. This procedure is accomplished by mounting custom components called "Bob Weights" to the rotor bearing journals of the eccentric shaft which from thereon stimulate the actual weight of the rotors themselves. REC has had a very specially designed custom Bob weight manufactured to allow us to accommodate all different weights of rotors within a tolerance of 1 gram. After the Bob weights are installed, the shaft is then dressed with the rest of the rotating components and counterweights. The rotating assembly is then spun to approximately 1200 RPM on the dynamic balancer. The balancer then electronically measures and points out the spots on the counterweights (or flywheel) where material needs to be removed.

Within ours sophisticated equipment the milling head can accurately be aligned to the spots with pinpoint placement. When it is determined that material needs to be removed, the correction can be performed while the rotating assembly is still fastened to the machine. In instances where weight needs to be added the counterweights and or flywheel are removed and remotely fitted with heavy tungsten metal slugs. We then perform a procedure to securely anchor these slugs of specified weight into the subcomponents. A final spool up and measurement is performed to check and finalize a perfect balance of the rotating assembly.

Prices for lightened assemblies (corrections to remove material)
10a, 12a & 13B: $170.00
20B & 3 Rotor: $235.00

Prices for heavier assemblies (corrections where material is added)
10a, 12a & 13B: $190.00-$260.00
20B & 3 Rotor: $255.00-325.00
Call for additonal information.

Factory Re-Balancing

Although Mazda factory rotating assemblies are balanced fairly accurately when produced, REC has perfected methods to increase accuracy and performance. One area of the rotating assembly which we have learned can be improved is the rotor itself. The rotor rebalancing is a procedure performed on just the rotor using a series of corrections and adjustments by removing material from certain areas of the rotor. This procedure is referred to as balancing the rotor on its own axis. With a specially designed custom arbor, and the use of our high end machine, we can determine where material needs to be removed accurate to half a gram.

The rotors which become candidates for rebalancing would be units which have been machined or altered in any way, rotors which has been lightened, clearance'd or had 3 mm slots milled into the apex's, are all good examples for units which should be rebalanced. When mixed and matched parts from different years and models are used it is always a good idea to perform this procedure. We recommend re-balancing factory, already balanced, rotors when building a performance or high-end engine which will be used for racing.

Re-balancing unmodified factory rotors, clearance rotors or rotors which have had apex modifications is one of the more straightforward applications for re-balancing the rotor on its own axis. In these circumstances we see limited or very little corrections to be made. Notwithstanding, this is still a very relevant and important procedure to complete. Rebalancing rotors which have undergone extensive modifications such as removing material to make the rotors the same weight or lightening rotor such as the CNC lightening which we offer, require more extensive work to accurately be re-balanced.

It is also recommended that once the rotors are balanced on their own axis, that the counterweight corrections and balancing of the entire rotating assembly becomes absolutely necessary.

Re-balance lightly modified rotors: $65.00 per rotor
Re-balance weight matched or lightened rotors: $90.00 per rotor

Flywheel & Clutch

REC offers rebalancing of your factory or aftermarket flywheel by itsself or with the clutch assembly. This procedure is performed by balancing the flywheel / clutch assembly on its own axis. For the ultimate smoothness and performance, this balancing process puts the final touch on any engine rotating assembly. When your parts are returned you will notice we have indexed the flywheel to counterweight and clutch to flywheel positions which must be reinstalled with these marks aligned. Although the flywheel can be balanced as part of the entire rotating assembly, we recommend balancing the clutch on its own axis with the flywheel assembly.

Flywheel balancing: $75.00
Flywheel & Clutch Assembly: $135.00

Counterweight Corrections

If you should so choose to swap out the engine rotors with a different model year or style of rotor or you have a pair of unknown counterweights, we can perform counterweight corrections only. Or, if you have a pair of rotors to which you know their actual weight in grams, and you wish to purchase a set of counterweights whereby we will perform the counterweight corrections only.

We give our customers the availability to either send us weights/flywheel or purchase them from us and either fax or e-mail us the actual weight of the rotors so we can send the customer a set of weights that will be at balanced matched to your rotating assembly.

Price range: $135.00-$325.00 plus weights