What is this-James Brake Decelerometer Gauge Instrument?

[Tom Laferriere]

Bought this and would like to know how it is used?

Thanks,

tom

[drwatson]

Googling seems to say it's a device used by aircraft. Here's one quote: "Initially the James Brake Decelerometer was used to obtain a measure of friction on contaminated runway surfaces. These friction values were referred to as the "James Brake Index" or JBI’s."

[MCHinson]

We use modern ones to measure the coefficient of friction for a roadway. That is used to calculate the speed of a vehicle from skid marks while doing traffic crash investigation. I guess this one is a very early one judging from the text on the face referring to a 20 mph speed for testing.

I would guess you would just secure it to a fixed location in the car, point the arrow as instructed, accelerate up to 20 mph, slam on the brakes and read the meter as you are skidding (or not) to a stop.

[Tom Laferriere]

Thanks all

[Guest De Soto Frank]

I think MC Hinson's explanation was probably most related

to your gizmo... sure is a neat-looking device.

I have seen pictures in a couple of 1940's vo-tech textbooks of a number of big drive-on brake-testers that were mfd in the '20s & '30s, that involved various drums and such that contacted the road wheels.

One model(Weaver?) had four vertical standards, at each corner, with a big dial gauge at the top of each, to indicate the braking effort of each wheel.

I believe they were designed to help service departments properly set-up and equalize mechanical braking systems.

[DJKSETX]

I was an enlisted USAF weather observer in the late 1960s at Reese AFB, Lubbock, TX. The Base Operations Ford station wagon had a flat mounting plate on the tranny hump less than a foot square. The decelerometer sat on it and when the runways were frosty the driver would run down the concrete, stomp the brake and measure how well the tires gripped. The weather observer was then required to encode a remark on the observation indicating that the braking action was poor etc. This was to prevent the 'Nam jet training aircraft from running off the end of the runway into the cotton fields.

DJ Kava

Beaumont, TX

[R Walling]

For the longest time, Ma. had a gauge that an inspection station operator hung on the drivers window and slammed on the brakes as part of the vehicle inspection station equipment.

I never seen one used in any test, but the private stations had to have one. And you bought it off of the Ma.Registry Inspector. (Cash, no doubt)

[Tom Laferriere]

You can have it for $300