police speedometer

[bmh]

What would be the differences between a police speedo with a handlock and a standard speedo? Was the same speedo used and a handlock kit added to it?
Brian

[Rubone]

It depends on the year and speedo type. Most police units were specially calibrated for accuracy. Some are identified as police on the face, some not. Some end at 100 MPH, some don't. Most early cases have the opening for a handlock setup so it can basically be added to any version. What year speedo?
Robbie

[bmh]

Was wondering about the 48-52 variety. The parts book doesn't list a police speedo, just the hand lock unit. If police and civilian used the same speedo, was the speedo modified for this application? Also how was the hand lock unit mounted?
Brian

[Chris Haynes]

48-52's all used the same speedometers. The electric stop was a police option added to them.

[Perry Ruiter]

48-52's all used the same speedometers. The electric stop was a police option added to them.

Sorry Chris I gotta disagree with you. There was a civilian and police version of the 48-52 speedo. There was no external marking on the face (in fact both speedometers were assembled from the exact same parts) just the calibration on the police speedos was held tighter. In round numbers typically civilian calibration is never slow and allowed to be up to 5% fast and police calibration as held within 1% slow or fast.
Anyway, the standard speedo for 48-52 was 509ET and police speedos were 509EV. Attached are an application sheet from Stewart Warner documenting this, an extract from a 1952 Stewart Warner speedometer parts book showing 509ET and 509EV and a couple photos of a 509EV can. Sorry folks I thought I had one with a clearer stamp but that's the best one I can put my hands on right now. Trust me it says 509EV. Another indicator is that police speedos were stamped with a P (pointed to by the arrow) ... Perry

[Perry Ruiter]

Also how was the hand lock unit mounted?
Brian

The little door held onto the speedo housing with two small screws is removed the speedo handlock is inserted and the screws hold it in place. The door is discarded. The dash base has a spring steel arm riveted to it that it used to reset the handlock. The arm has a button riveted to it that sticks out the small hole on the left side of your dash cover (that 's what the little hole with the plug in the cover is there for). Let me know if you want pictures of this setup ... Perry

[INLINE4NUT]

Perry if it isnt to much bother please post those pics as well Im just a little curious !! Thankyou !!

[bmh]

Thanks Perry, would also love the pics. Someone had told me that the handlock was controled by a button on the bars. Was it locked by the button on the bars and reset at the dash? or am I wrong about the button?

[Chris Haynes]

Thanks Perry, would also love the pics. Someone had told me that the handlock was controled by a button on the bars. Was it locked by the button on the bars and reset at the dash? or am I wrong about the button?

You are correct.

[Perry Ruiter]

Thanks Perry, would also love the pics. Someone had told me that the handlock was controled by a button on the bars. Was it locked by the button on the bars and reset at the dash? or am I wrong about the button?

The 38 and later handlock is activated by a second horn button on the throttle side (a tip off that your bars were originally from a police bike is if they have two horn buttons on them) and then reset by the arm riveted to the forward left of the dash base. The handlock is a small electromagnet. When you push the button on the bars the centre is pulled in and the nose presses against the speed cup inside the speedo. This prevents the speed cup (and hence needle) from moving and the bike can speed up or stop with the needle remaining frozen in position. Once the centre is pulled in a spring loaded arm snaps over it and holds it in the in position (so you don't need to keep your finger on the button on the bars). To reset and allow the needle to return to zero you push the button sticking out the side of the dash cover. This pushes against the spring loaded arm and allows the center to pop back out thus releasing the speed cup.

Hopefully the attached pictures make clear how things work. I'm embarrassed to say I don't have a base with the reset arm still riveted on. So the reset arm is held in place by toothpicks in the photos. Those toothpicks should be rivets in the real world.

A couple more points - first, this only applies to 38 and later. 36 and 37 had a different set up that was completely mechanical (a push/pull "button" on the handlebars operated a cable that pushed the center nose against the speed cup). This set up was only available for 36 and 37 speedos that had a trip odometer. It wasn't available for a non-trip speedos. Second there are several variants of the small electromagnet. The short nose is for the 509 series speedos (61 and earlier). The long nose is for the 540 series speedos (62 and later) and there are 6 and 12 volt versions of it. In the attached photos the 509 handlock (short nose) has the centre held in. The 540 handlock (long nose) has the centre out ... Perry