Replacing speedo gear

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Tunglegubbin
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Replacing speedo gear

#1

Post by Tunglegubbin » Sun Oct 07, 2012 8:23 pm

I need to move the speedo gear from my original countershaft to my new aftermarket one.
I cannot find the procedure for this.

Do I just grind out the stake marks and then press it off?
Does quick heating, so it wont have time to transfer to the main gear, help?

/Mikael



Cotten
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Re: Replacing speedo gear

#2

Post by Cotten » Sun Oct 07, 2012 8:56 pm

Mikael!

Please do not heat or grind.
The drive gear should press on cold, but trued with a dial indicator between centers.
Please avoid tapping upon the gear near the ends of teeth, as it is quite brittle.

Your aftermarket countershaft cluster gear may be at variance, so please inspect all dimensions closely!

....Cotten

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Re: Replacing speedo gear

#3

Post by 1950Panhead » Sun Oct 07, 2012 11:11 pm

Your aftermarket countershaft cluster gear may be at variance, so please inspect all dimensions closely!
After you press the speedo gear off use a micrometer, measure old ring and new ring.
Jerry

Robert Luland
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Re: Replacing speedo gear

#4

Post by Robert Luland » Sun Oct 07, 2012 11:24 pm

And soon as you get ready to press it on the new cluster you will find it's to loose. Get ready to tack weld it on. You don't have to go nuts with the welder. just a couple of tacks on each side will do. Remember it's only turning a fiber speedo gear. Here's picture of how I do it. Make sure ya use the little c clamps to keep it centered and from drifting from welding shrinkage. Bob L
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Re: Replacing speedo gear

#5

Post by Cotten » Mon Oct 08, 2012 3:47 pm

Folks,

The factory did not weld the gears in place for obvious reasons:
not only does it distort the worm, it softens it near the welds.

If the worm gear is loose upon the clustergear, replace one or the other until a press-fit is achieved.
A simple press-fit (.0015") is all that is necessary to retain the gear, although a loctite-like compound may assist a looser fit.
It must be trued to the clustergear between centers, and a single weld tack risks skewing it from running true.
WORMTRUE.jpg
....Cotten
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Re: Replacing speedo gear

#6

Post by Robert Luland » Mon Oct 08, 2012 4:04 pm

Tom, why don't we just call up them poor unemployed NASA engineers and get a straight answer. They stacked the damm thing because they were cheap and it was the fastest down and dirty way to pull it off. Every one of these I've pressed off has been dangerously loose and no Lock-Tite goup is going to cure it. The gear is the same width as the shoulder on the gear. If ya clamp the thing with four little c clamps, it's going to be centered. I've never had a bit of problems with the ones I've tack welded but I can tell ya this. I also never spent an hour minimum chocking one up in a lathe with a dial indicator either. I got better things to spend my time on. Bob L

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Re: Replacing speedo gear

#7

Post by Cotten » Mon Oct 08, 2012 4:30 pm

Who among us has ever encountered a worm gear that has come off?

.....Cotten

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Re: Replacing speedo gear

#8

Post by Tunglegubbin » Tue Oct 09, 2012 9:13 pm

Thank you guys!

Tonight I thought I should try and get my gear off so I made a support ring to press against the inside diameter of the gear so I wouldn't chip any teeth.
IMG_2043.jpg
IMG_2044.jpg
Turned out the fit was not so strong, didn't take much to get it off, much easier than expected.
IMG_2045.jpg
Measuring my parts turned out something interesting.
The original gear seating area diameter is 55.635mm
My new aftermarket is 55.615mm
The speedo gear inside diameter is 55.655mm, its actually bigger than even the original gear.

So how does it stay on? Well the cross stake marks diameter is just 55.620mm.
Test mounting the speedo gear on my new shaft will give marks only where the stake marks are.

Could it be that the gear is not actually staked in place after mounting but that the gear is staked prior to assembly to provide the press fit?
Seems easier than machining press fits for parts that don't do much work.

The press fit I get now seem equally tight as original.
Im gonna see what Loctite bushing assembly fluid is suitable and add that for peace of mind.

The idea of welding things on my hardened gearbox parts, even though it might work, just seems wrong?
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Re: Replacing speedo gear

#9

Post by Robert Luland » Tue Oct 09, 2012 9:25 pm

Interesting pusher ya made there. Good job but I'm lazy. I just use a 2" pipe coupling in the press. The more I read this thread the more concerned I'm getting. Anybody here got a inside number for the Jet Propulsion Laboratory in Pasadena? Just kidding! You're doing a fine job lad. Bob L

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Re: Replacing speedo gear

#10

Post by Cotten » Tue Oct 09, 2012 10:41 pm

Tunglegubbin!

Your instincts are good.

As I tried to express earlier,
the gear does not need to be extremely tight to stay put.
If it runs true on the clustergear, there is no side thrust;
Even the drive gear through the case will limit it from "walking off" sideways, as it is quite firmly supported in its axis.

Perhaps some fear that the speedometer might freeze, and lock up the transmission?

Your new clustergear shaft does seem small.
Averaging three OEM originals out of the bin gives an average of 55.652mm;
That's about a three and a half thou press into a nominal 2 3/16" bore, or 55.563mm. (More press than I suspected...)

An OEM clustergear will not take a knurl, but an aftermarket might.
It won't need much!

....Cotten

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Re: Replacing speedo gear

#11

Post by Robert Luland » Wed Oct 10, 2012 2:38 am

Perhaps some fear that the speedometer might freeze, and lock up the transmission?

That's why the factory used a fiber gear on the cable drive. To cover there shit engineering job!

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Re: Replacing speedo gear

#12

Post by Cotten » Wed Oct 10, 2012 4:28 pm

Robert Luland wrote:Perhaps some fear that the speedometer might freeze, and lock up the transmission?

That's why the factory used a fiber gear on the cable drive. To cover there shit engineering job!
Uh Robert,

The factory used steel for the cable drive gear on Big Twins.
45s had fiber, and they always seem to break if you do not pull them before removing the brake drum.

....Cotten

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