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#553356 - 07/17/14 3:25 pm Smith's Chronometric speedo disassembly?  
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zoe Offline
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How do remove the trip meter re-setting shaft so you can remove the speedo movement from its housing?

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#553372 - 07/17/14 4:38 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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gREgg-K Online content
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Ottawa, Canada
If it is the type that exits the rear of the housing, the knob is held to the shaft by means of a tiny cotter pin.

Sometimes the pin is rusted in place, and needs to be drilled out. The knob is sometimes rusted onto the shaft, as well.

... Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#553398 - 07/17/14 7:01 pm Re: Smith's Chronometric speedo disassembly? [Re: gREgg-K]  
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To remove the movement from the case you need to first remove the reset knurled knob by removing the cotter pin.Then take off the bezel and glass then the 2 screws at the back this will allow enough movement for the reset pin to be lightly pushed into the can and the complete mechanism removed from the can.

#553404 - 07/17/14 7:39 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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downhere Offline
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I repair these as a hobby if you need any more information.

#553460 - 07/18/14 4:09 am Re: Smith's Chronometric speedo disassembly? [Re: downhere]  
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Ponce Offline
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Hi Downhere,
Can U tell me please what type of lubricant U use on the drive shaft in the speedo. Someone said ordinary grease but I suspect it may be hard to turn when in the cold weather. Hope U can help, thanks.
Ponce

#553595 - 07/18/14 8:17 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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downhere Offline
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Modern grease will be fine, but sparingly so it doesn't splatter over everything else. You can't remove it before removing other things if that was your plan.

#553631 - 07/19/14 12:44 am Re: Smith's Chronometric speedo disassembly? [Re: downhere]  
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zoe Offline
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Thanks for the information.

I unscrewed and removed the bezel and glass. Got the knob off the reset shaft and removed the movement from the can. Everything inside looks to be in good condition but when the drive is turned, as if there were a turning cable in it, the needle doesn't move. Lots of the little gears in there move and there is a watch-like mechanism that seems to be working. It worked perfectly up until a couple of days ago. I like to try to fix stuff myself but I'm at a loss on this one.

Have any of you successfully repaired one of these 1960 vintage Smith's Chronometric speedos? What should I be looking for?

Bob

#553665 - 07/19/14 4:51 am Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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Originally Posted By: zoe
<SNIP> It worked perfectly up until a couple of days ago. I like to try to fix stuff myself but I'm at a loss on this one.
Have any of you successfully repaired one of these 1960 vintage Smith's Chronometric speedos? What should I be looking for?

Bob

Bob, You may have thought of this, but just in case: have you tried driving your speedo counter-clockwise, as viewed from the rear of the instrument? They were made in both types.

Chronometrics are not rocket science, but (speaking as someone who restores them), you need a delicate touch and the right tools, or you may be worse off if you dismantle it.

Check the "comb spring" in the mechanism ... are all its leaves in good condition and not broken? Could also be that one of its leaves is no longer correctly engaged with the mechanism.

.. Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#553686 - 07/19/14 9:10 am Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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As Greg says you need to confirm the correct direction of rotation, once you have established this ,if it still doesn't move you need to check that the driving pin on the second gear counting from the top is not broken off it is about 3/16 long and is attached to the top of the second gear and engages the top gear (the disc with no teeth) and this drives the needle.A simple check is to manually move the needle to say 40 MPH and the needle should stay there and you will feel a light ratcheting as it moves, if it just moves back to zero once you release it the pin is likely broken off.If it stays at 40 to return it to zero put a square drive or cable in the drive and just flick it and the needle will return to zero.Also check the plate that locks the input drive gear to the gear frame,it is just above the cable and held with one screw,take it out and check for wear on the under side any visible wear causes the mechanism to work intermittently, turn the plate over and reinstall.I've found that even wear as little as .006 was enough to upset the drive.This wear is caused by the cable "stand-off" being too long and it pushes up on the input gear.

#553758 - 07/19/14 5:50 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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zoe Offline
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Gregg & Johnnie,

It turns counterclockwise when viewed from the back.

When I move the needle up to about 40 mph (slight ratcheting sound) and then turn the drive in the correct rotation the needle pops back to zero.

The little pin I think you are referring to appears to be intact and in the proper position.

What must be the comb spring has four (I think) leaves on it, three of which appear to be in the same plane, the other one is not in the same plane. Maybe this is the problem?

Like I said earlier this speedo worked perfectly and then just stopped working at all.

Bob

#553770 - 07/19/14 8:15 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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I'm staying out of this now. If it worked before then don't touch anything until you've pulled one apart 100 times!

#553953 - 07/20/14 6:44 pm Re: Smith's Chronometric speedo disassembly? [Re: downhere]  
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zoe Offline
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Is the book "Magnetic Speedometer Repair" from the UK worthwhile?

My odometer and trip meter work fine but the MPH needle doesn't work. A few days ago it worked very smoothly and then it just stopped working as if the cable had broken. The cable is good.

All of the intricate internal parts appear to be clean and they turn/move when I apply the proper rotation to them with my drill motor.

Should all of the comb spring plates/tines be in the same plane or should one of them sit at a different angle?

Bob

#554000 - 07/20/14 11:32 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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gREgg-K Online content
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Originally Posted By: zoe
Is the book "Magnetic Speedometer Repair" from the UK worthwhile?

My odometer and trip meter work fine but the MPH needle doesn't work. A few days ago it worked very smoothly and then it just stopped working as if the cable had broken. The cable is good.

All of the intricate internal parts appear to be clean and they turn/move when I apply the proper rotation to them with my drill motor.

Should all of the comb spring plates/tines be in the same plane or should one of them sit at a different angle?

Bob

Bob,
Thought I would answer your PM here, so that more people would benefit from the answer.

1. The "Magnetic Speedometer Repair" book from the UK does not deal with Chronometrics at all. In fact, it even overlooks some very important aspects of the Magnetic instruments, like how you dismantle the main spindle in order to lube it ... possibly the most important aspect of the task.

2. The comb Spring has 4 tines/leaves, each of which is different in length and/or shape. The top leaf has a small kink at its end to serve as a detent for the disk it rides on, and the second from the top is bent noticeably outward and must sit between the tines of a curved fork. I've seen this leaf bent and not correctly engaged with the fork. The lower leaves are what give the ratchet sound your hear.

.. Gewgg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#554001 - 07/20/14 11:55 pm Re: Smith's Chronometric speedo disassembly? [Re: gREgg-K]  
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Bob,

Just had another thought: on the very right hand side of the speedo mechanism there is a vertical shaft with an extremely fine gear cut into its surface. This is teh so-called "rocking shaft", and its purpose is to drive the gear linked to the needle.

Could be the gear is stripped, badly worn, or the rocking shaft is stuck in the outward extremity of its travel and no longer engaging with the driven gear.

.. Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#554114 - 07/21/14 3:20 pm Re: Smith's Chronometric speedo disassembly? [Re: gREgg-K]  
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Gregg,

Thanks for staying with me on this issue.

Your latest post is close to the issue I must resolve.

I've now got the Chronometric movement removed from the odometer/trip meter frame. Again everything looks very good but the lever on the end of the rocking spindle which has one end "hook shaped", that hook which should capture the end of the tine on the bent tine of the comb spring, but it has slipped out of position so it no longer captures that tine on the comb spring. I have repositioned it correctly but, due to the rocking spindle being tipped at a slight angle, I'm afraid the bent tine of the comb spring will move out of that hooked end of the lever again. Do you have any idea how I can prevent that from happening?

The very fine gear teeth on the Rocking Spindle shaft look good.

Gregg, Upon further examination I feel I need to remove the Rocking Spindle, complete with the lever which has the hooked shaped end on it and put a slight bend in that hooked portion so it will be centered on the comb spring tine and remain there. Better yet, without removing it, I believe I could put a very slight bend only in the portion of the hook which contacts the spring and that way I wouldn't change the portion that contacts the cam. Having been a dentist for forty-three years I have access to very special little wire bending pliers which would do this job.

Thanks again, Gregg, for your help. I'm waiting to hear from you before I do something I might regret.

Bob

Last edited by zoe; 07/21/14 4:18 pm.
#554146 - 07/21/14 7:24 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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Bob,

Not sure about bending the lever that has the hooks to capture the comb spring leaf. I've never tried (nor had to) bend one, because to me it looks hardened, and I fear it would snap if bent.

I suggest you find a different way to align the parts, since I believe that is the cause of your problem. IN your shoes, I would slacken the screws that retain the comb spring, and move it slightly to better engage the hooks.

Good luck!
... Gregg (aka SpeedoMan)


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#554156 - 07/21/14 8:56 pm Re: Smith's Chronometric speedo disassembly? [Re: gREgg-K]  
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Thanks for your reply, Gregg. I tested the speedo with the hook properly aligned on the comb spring tine and it works properly. I know the finger on the hook won't stay there unless I do something.
Your comment about that part being hardened concerns me. How I can get those two parts to remain aligned perplexes me but I will give it some thought.
Thanks again for your input.
Bob

Last edited by zoe; 07/21/14 9:08 pm.
#554168 - 07/21/14 10:08 pm Re: Smith's Chronometric speedo disassembly? [Re: zoe]  
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Originally Posted By: zoe
Thanks for your reply, Gregg. I tested the speedo with the hook properly aligned on the comb spring tine and it works properly. I know the finger on the hook won't stay there unless I do something.
Your comment about that part being hardened concerns me. How I can get those two parts to remain aligned perplexes me but I will give it some thought.
Thanks again for your input.
Bob


You're welcome, Bob, and I'm pleased we were able to zero in on the cause. As regards whether the hook bit is hardened or not, I don't know that for a fact ... but if the part looks flat, I would leave it alone ... those parts are very scarce if you break it, and with a hardened part, you won't get much warning.

Did you try releasing the two tiny screws that secure the comb spring and re-aligning it? That usually works.

. Gregg


Spyder Integrated Technologies
Lucas, BTH, & Miller Magneto & Dynamo Restoration
SMITHS Chronometric Restoration
magneto@spyder-it.com
#554176 - 07/21/14 11:06 pm Re: Smith's Chronometric speedo disassembly? [Re: gREgg-K]  
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Thanks, Gregg. I'll try realigning the comb spring tonight. The problem seems to be a little too much play in the bushing on both sides of the flat lever with the hook in the end or the bore of that flat lever with the hook on the end has worn to allow it to sit at an angle on its shaft instead of at 90*.
I might be able to take that wobble out if I removed the screw holding its shaft to the brass plate and filed about .001" or .002" off the end of the shaft. That would tighten things up a bit and probably help maintain the alignment of the two parts. I can see the tiny wear mark on the spring and the finger on the lever has always been close to sliding off the side of the spring.

Bob

#560410 - 08/27/14 11:51 am Re: Smith's Chronometric speedo disassembly? [Re: downhere]  
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Jerry Roy Online content
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Originally Posted By: downhere
I repair these as a hobby if you need any more information.


Howdy DH

I'm not Zoe, but I share his enthusiasm for doing everything he can on his bike. So I will take you up on your offer.
I am restoring a BSA GS that I parked 45 years ago.
The "clocks" are in need of refreshing. One of the bezels have chrome flaking off, and the tach has some rust around the center of the needle. Can new bezels be purchased, and from where?
The tenths dial on the speedo has the color faded to a light brown, but the rest of the numbers look OK. How does one restore the orange color to the numbers? J. Jones, in his article, http://www.hells-confetti.com/Technical%...%20Overhaul.pdf
states that they can be cleaned with soapy water and a cotton swab. Does that jibe with your experience?
And what sort of cleaning do you use? Can an assembled unit be put in an ultrasonic cleaner, minus the number wheels, and be cleaned that way?
What sort of lubrication do you recommend? I have some instrument oil that is supposed to be for clocks, etc.
Can the rubber glass gasket be purchased, and if so, from who?
Thank you for sharing any hints or tips that you can.

Jerry Roy


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