Speedometer Question

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Bikesmith01
Posts: 24
Joined: Sun Jul 12, 2020 4:55 pm

Speedometer Question

Post by Bikesmith01 »

Hey Friends!
I'm working on my speedometer today and something has me puzzled.
So the speedometer part of my VDO speedometer is working great, but the odometer isn't moving. I've opened it up. I disassembled it, cleaned it, and put it all back together. Still not working. I can see exactly where the issue is, but not what the solution should be.
https://freeimage.host/i/22zWcF
Here's what I'm looking at. The shaft that goes through the middle of the odometer spins, driven by gear A (itself driven by a worm gear from the main input). That shaft should spin wheel B, which drives the whole odometer. If I spin wheel B by hand everything works perfectly. The odometer clocks up the miles as it should.
But I don't see any mechanism to transmit torque from the shaft to wheel B. It just spins freely on the shaft. I'd expect to see the shaft keyed to the wheel somehow, but there's nothing. A perfectly smooth shaft through a perfectly smooth hole, which somehow needs to transmit torque.
What the heck am I missing?
Thanks for your help!
-Jon
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Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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schrader7032
Posts: 7402
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: Speedometer Question

Post by schrader7032 »

Never seen the inside of a /2 speedo...only the later ones.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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Bikesmith01
Posts: 24
Joined: Sun Jul 12, 2020 4:55 pm

Re: Speedometer Question

Post by Bikesmith01 »

Update:
I used a teeny, tiny drop of sleeve retaining compound applied to the bore of wheel B with a dental pick. It actually worked perfectly. Everything is reinstalled and fully functional. Speedo and odometer working correctly.
It still seems wrong, though. Something so exquisitely engineered shouldn't rely on glue to work properly. I'm still curious if any of you know how that interface is intended to work.
I'll certainly be opening up that speedo again. This was a functional pass. I'll be going back through for a cosmetic pass at some point (I want to cut new glass for it, polish everything, replace the bezel, etc.), so if there's a better way to set it up I'll do it.
Thanks!
-Jon
******************************************************************
Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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schrader7032
Posts: 7402
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: Speedometer Question

Post by schrader7032 »

On the /7 instrument pod, typically what happens is that the odometer quits working. Turns out the tenths wheel slides to the side and no longer engages the rod. The fix is sort of like what you did...put a but of JBweld (or similar) on the wheel to secure it to the rod.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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jwonder
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Joined: Wed Nov 23, 2016 7:50 pm
Location: Long Island, New York
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Re: Speedometer Question

Post by jwonder »

Jon,

This is VERY COMMON and I know Joe at Joe's Speedometer has the parts (he fixed mine). I would email him and see if he will sell you the parts to fix it. You will need a new bezel as well I would think.

James
James Wonder
1967 R69S, 1966 R50/2, 1965 R27, 1963 R27, 1952 R51/3 and 2018 R1200GS
Long Island, New York

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Bikesmith01
Posts: 24
Joined: Sun Jul 12, 2020 4:55 pm

Re: Speedometer Question

Post by Bikesmith01 »

Update 2:
The speedometer continues to work perfectly. I just wanted to share something I figured out for reassembly. Forgive me if this is common knowledge, but maybe it will help someone:
I used to lathe to carve a shape into a block of wood (see photo) that was a tight fit on the bezel. Then I assembled speedo, glass, and bezel in the wood and carefully used a hammer and drift to crimp the bezel. Worked perfectly.
Also, my bike came without the trip odometer reset knob. So I made one out of titanium. Not a useful thing to share. I'm just kind of proud of how it turned out. You can see it in the second photo.
-Jon
wood.jpg
Speedo.jpg
******************************************************************
Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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palica
Posts: 34
Joined: Sun Jun 28, 2020 10:22 am
Location: Montreal, Qc, Canada

Re: Speedometer Question

Post by palica »

Result is superb. I love the titanium reset button :D
1967 R50/2 with Duna sidecar
1974 R90S

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goaarongo
Posts: 45
Joined: Wed Apr 11, 2018 10:40 pm

Re: Speedometer Question

Post by goaarongo »

I'll take a number for one of those knobs. Mine is missing too. Honestly was never sure what (if anything) went there...

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schrader7032
Posts: 7402
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: Speedometer Question

Post by schrader7032 »

Not sure if something at McMaster Carr might work as an interim solution:

https://www.mcmaster.com/threaded-knobs ... e-knobs-6/
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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Bikesmith01
Posts: 24
Joined: Sun Jul 12, 2020 4:55 pm

Re: Speedometer Question

Post by Bikesmith01 »

A threaded knob won't work. The shaft isn't threaded. It has a dimple to accept a set screw in the knob.

With a lathe it's a pretty straightforward part to make. Even without a lathe you can make a decent one:
The shaft is 3mm diameter. If you're lucky you can find a knob with a 3mm hole. Otherwise, find a knob with a hole smaller than 3mm (or no hole at all) and drill it out to 3mm. This fit needs to be pretty precise. For the rough draft of the knob I made I just used whatever drill bit I had that was close to 3mm. It was a bit too big. Tightening the set screw into the shaft dimple skewed the knob so it sat at an angle. Second attempt I used an exactly 3mm bit and it worked perfectly.

Next, measure the distance from where you want the bottom of the knob to be (close to, but not touching, the glass) up to the center of the dimple on the shaft. Note that the shaft can move up and down a little bit (or at least mine can) because of play in the bevel gear at its other end. You want to take the measurement with the shaft at its lowest position. Otherwise you might end up with a knob that rubs against the glass. Mark a spot on your knob that distance from the bottom and drill and tap it. It helps to drill not just into the center bore but partway into the other side. That allows you to tap the hole completely without worrying about bottoming out the tap. I used a 2.5mm set screw, but I don't think the size is critical. With a larger set screw you'll just need to make sure to dress the tip so it fits into the dimple on the shaft. Be careful with the tiny drill bit and tiny tap. It's easy to break them off in the knob. Ask me how I know :lol:

That's it. Just any old knob, with a 3mm hole in the bottom and a set screw in the side at the appropriate height from the bottom. I think you could even use plastic. It's a pretty low stress application. I just used titanium because I wanted to bring the weight of the bike down ;)

Next task - Custom titanium tickler buttons!
******************************************************************
Jon the Bikesmith
1959 BMW R60
1940 Royal Enfield WD-C/O
1942 Chevy 3/4-ton special Flatbed
1985 BMW K100RS
******************************************************************

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