Oehler Research · Ballistic Chronographs
Oehler Model 35x2
A two-way chronograph that captures inbound and rebound velocity in one pass and computes the coefficient of restitution (COR) on every shot.
The Model 35x2 is a two-way chronograph designed for rebound testing. A ball is fired at a rigid plate; the instrument measures the inbound velocity, then the ball rebounds back through the same screens and the rebound velocity is measured. The ratio of the two is the coefficient of restitution (COR). COR is a key performance and compliance figure for golf, tennis and baseball equipment, and because Taiwan is a major manufacturing base for golf clubs and sporting goods, R&D and QC teams here need a measurement baseline that matches international practice. The sensors are Model 57 infrared screens, unaffected by room lighting; in a rebound setup they detect objects larger than .17 caliber traveling faster than 300 fps. Output is a 2.25 in adding-machine tape printer with a replaceable ink roller.
Overview
The difficulty in COR measurement is that one set of sensors must handle two passes in opposite directions within a very short time, and the second pass is much slower than the first. The Model 35x2 builds the measurement zone from two Model 57 infrared screens: it records the inbound velocity as the ball enters, then the rebound velocity as it comes back through the same zone after striking the rigid plate, and computes and prints the COR for each shot. Because the screens carry their own infrared source, lighting inside the test chamber does not affect the result. In the rebound setup the detection limit is .17 caliber and 300 fps (the Model 57 on its own is rated down to 250 fps under the best conditions); for larger, slower balls, low-velocity screens are available. Power is 120V AC stepped down to 9V DC by a plug-in transformer; output is a 2.25 in adding-machine tape printer with a replaceable ink roller.
Key specifications
| Purpose | Rebound testing of sporting balls (golf, tennis, baseball and similar) |
|---|---|
| Measurement | Two Model 57 screens capture both inbound and rebound velocity |
| Screen capability | In the rebound setup, detects objects larger than .17 caliber and faster than 300 fps (Model 57 alone is rated down to 250 fps under the best conditions) |
| Computed output | Coefficient of restitution (COR) computed automatically per shot |
| Output | 2.25 in adding-machine tape printer with replaceable ink roller |
| Power | 120V AC stepped down to 9V DC by a plug-in transformer |
Features
Both velocities from one pass
Inbound and rebound velocity come from the same screens in the same test; no second instrument to synchronize.
COR computed per shot
The coefficient of restitution is calculated and printed at once; no conversion by hand afterwards.
Infrared screens unaffected by lighting
Uses the Model 57's own infrared source, so the lighting in the test chamber does not change the result.
Low-velocity screens available
Extends the measurable range to larger, slower balls.
Tape printout for the file
The record attaches directly to the test report; the ink roller is replaceable.
Measurement setup and applications
SENSOR LAYOUT · SENSORS
Two Model 57 units form the measurement zone
The ball passes through the same zone going in and coming back; the active infrared source keeps chamber lighting from affecting the trigger.
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