The Ford Barn - View Single Post - Round speedometer adjustment/calibration ?

160B · 03-03-2018, 06:52 PM

Leave the hair sping as it is. Calibration is accomplished by moving the adjusting plate on the bottom of the magnet.

The paragraph below is from the article by Gordon Fischer of THE BEAVER CHAPTER, MAFCA Portland, Oregon

http://www.modelahouse.com/tech/spee...r/fischer.html
CALIBRATION

The odometer and trip are gear driven and no adjustment can be made. Drive a measured mile, or better yet five miles, at any speed. If the odometer and trip do not agree with the measured distance, the gear, in the gear box on the drive shaft, is probably incorrect for the ring gear, or the tires and wheels. A good speedometer shop can supply a correct gear box to make the odometer accurate. With the odometer accurate, the speed reading can be varied a few mph by moving the adjusting plate on the bottom of the magnet. Moving the plate counter clockwise (looking at the magnet from below) will make the speed read faster, move it clockwise for a slower speed-reading. A variation of from 4 to 6 mph is possible, if the magnet is strong. The tension on the hairspring will also have a substantial effect. The spring must just have tension to return the speed cup to a positive 0 every time. The most accurate way (outside of a speedometer shop) to check the speed calibration is to compare it with the speed of a modern car at the speed you usually drive, probably about 40 mph. You can also time how many seconds it takes you to drive one measured mile at any steady speed. Divide those seconds into 3600 to find the true speed. If your speedometer is accurate at a speed of 30 or 40 mph, it is as accurate at all other speeds, as it can be made. That part is built in (partially into the decal), and there is no adjustment.

The calibrating plate on the magnet (fig. 1) can be adjusted while the speedometer is completely assembled. Once you have determined that the odometer measures the correct mileage, you can calibrate the speed dial, if it is off a little. Make the tools shown in figure 13, only the 7/16" dimension must be exact. On the back of the case, remove the plug located immediately above the screw head. Insert the 7/16" end of tool #7 through

03-03-2018, 06:52 PM	#4
160B Senior Member Join Date: Aug 2010 Location: Port Orchard, WA Posts: 1,498	Re: Round speedometer adjustment/calibration ? Leave the hair sping as it is. Calibration is accomplished by moving the adjusting plate on the bottom of the magnet. The paragraph below is from the article by Gordon Fischer of THE BEAVER CHAPTER, MAFCA Portland, Oregon http://www.modelahouse.com/tech/spee...r/fischer.html CALIBRATION The odometer and trip are gear driven and no adjustment can be made. Drive a measured mile, or better yet five miles, at any speed. If the odometer and trip do not agree with the measured distance, the gear, in the gear box on the drive shaft, is probably incorrect for the ring gear, or the tires and wheels. A good speedometer shop can supply a correct gear box to make the odometer accurate. With the odometer accurate, the speed reading can be varied a few mph by moving the adjusting plate on the bottom of the magnet. Moving the plate counter clockwise (looking at the magnet from below) will make the speed read faster, move it clockwise for a slower speed-reading. A variation of from 4 to 6 mph is possible, if the magnet is strong. The tension on the hairspring will also have a substantial effect. The spring must just have tension to return the speed cup to a positive 0 every time. The most accurate way (outside of a speedometer shop) to check the speed calibration is to compare it with the speed of a modern car at the speed you usually drive, probably about 40 mph. You can also time how many seconds it takes you to drive one measured mile at any steady speed. Divide those seconds into 3600 to find the true speed. If your speedometer is accurate at a speed of 30 or 40 mph, it is as accurate at all other speeds, as it can be made. That part is built in (partially into the decal), and there is no adjustment. The calibrating plate on the magnet (fig. 1) can be adjusted while the speedometer is completely assembled. Once you have determined that the odometer measures the correct mileage, you can calibrate the speed dial, if it is off a little. Make the tools shown in figure 13, only the 7/16" dimension must be exact. On the back of the case, remove the plug located immediately above the screw head. Insert the 7/16" end of tool #7 through __________________ 1931 160B & 1931 68B If you don't have time to do it right the 1st time, how do you have time to do it the 2nd time?