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The Atlas Thread

Norton Models (not Commando or P11)

Re: The Atlas Thread

Postby kernel65 » Wed Mar 18, 2015 1:24 pm

Does anyone know if any 2:1 speedometer drive will work on the Atlas? Mine crapped out (I can turn the inner cable with my fingers and have a clunking sound in the drive). If not, what is the correct BG number?

Scott
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1965 Norton Atlas
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Re: The Atlas Thread

Postby texasSlick » Wed Mar 18, 2015 2:51 pm

Scott

Pt No 24563 is drive gearbox. I do not know if you can sub any 2:1 GB. Perhaps internals can be swapped from one 2:1 to another.

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Re: The Atlas Thread

Postby BillT » Wed Mar 18, 2015 3:06 pm

kernel65 wrote:Does anyone know if any 2:1 speedometer drive will work on the Atlas? Mine crapped out (I can turn the inner cable with my fingers and have a clunking sound in the drive). If not, what is the correct BG number?

Scott


BG1508/05
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Re: The Atlas Thread

Postby kernel65 » Wed Mar 18, 2015 3:44 pm

Thanks guys but those look like Tach drives. I'm looking for a speedo drive.

I found part number 22888 and a cross to BG 5330/257.

I did see one /257 on ebay in England but would any other BG 5330/XXX work?

Scott
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Re: The Atlas Thread

Postby texasSlick » Wed Mar 18, 2015 5:05 pm

Scott

I must be getting dyslexic in my old age .... I read that as tachometer drive.

Ok .... I am fairly well certain any 2:1 speedometer GB drive pt no 5330 will work. However, the center hole in the housing varies for the bike application, and the suffix after the "/" refers to the hole diameter variant. The bike mfgr inserts a spacer in that hole to fit the GB to the axle.

I recently bought a NOS GB on EBay which had a 0.750 hole. Time Warp graciously turned me a spacer to reduce the hole diameter to the stock Atlas value which eludes me .... I have it at my office and can PM it tomorrow, or you can press out your top hat spacer and measure the diameter.

Good Luck on finding a replacement. There are newly made knock-offs, but posters on this forum have generally been not satisfied with the life expectancy of the knock-offs. I would feel more comfortable with a genuine used Smiths.

It is possible to transfer the innards from one housing to another to get around the hole diameter problem.

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Re: The Atlas Thread

Postby BillT » Wed Mar 18, 2015 5:40 pm

I misread it, too. Sorry.

Yeah, BG5330/257 for speedo drive. The /257 designation means its a 2:1 reversing gearbox with the center hole sized for the Norton spindle spacer. Specified for most of the Nortons and Norton-wheeled hybrids until the Commando

According to my Smiths manual, the other 2:1 5330 boxes are:

BG 5330/31
BG 5330/247
BG 5330/287

The manual does not give the spindle hole diameters on any of these boxes, but the /31 is the box for certain BSA Starfires and Victors, and the /247 and /287 are the boxes for most of the BSA/Triumph twins
'73 Norton 850 Commando - 3030xx
'69 Norton Ranger 750 - P11/1289xx
'67 Matchless G15CS - G15CS/1235xx
'61 Matchless G80CS - 61/G80CS/41xx
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Re: The Atlas Thread

Postby texasSlick » Fri Mar 20, 2015 9:00 am

The hole diameter on the Atlas Speedo GB is 0.665 inches. My original GB obliterated the model / Suffix number when it jammed up and twisted itself into the hub, so I do not know the suffix number.

I recently purchased a 5330 / 287 NOS GB which has a center hole of 0.750 diameter.

The center hole in the GB for the Atlas spindle has a diameter of 0.570 - 0.572 inches. Norton fits a top hat bushing into the 0.665 hole to sleeve it down to 0.570.

Any 2:1 5330 GB should work by boring / sleeving the center hole.

Slick
Last edited by texasSlick on Fri Mar 20, 2015 12:49 pm, edited 2 times in total.
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Re: The Atlas Thread

Postby dynodave » Fri Mar 20, 2015 11:43 am

The basic 5330 comes in 2:1 and 12/15 (1.25:1) drive ratio. So it will fit...yes.. but not work to correctly indicate speed without the correct speedo..
I'm measuring the axle as .562" or 9/16". The swing arm slot as .570 and the speedo GB top hat spacer as .570 also.

FWIW
If 2:1 then the drive dogs are solid.
If 1.25:1, the twin drive dogs have holes drill in the face of the dogs.
A 1.25 can be made into a MKIII reverse rotation by completely demanufacturing a regular commando GB and reversing the components of the shaft components...done it several times.
Last edited by dynodave on Sat Mar 21, 2015 6:12 am, edited 1 time in total.
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Re: The Atlas Thread

Postby texasSlick » Fri Mar 20, 2015 12:47 pm

I have edited my previous post to clarify it and be consistant with Dynodave.

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Re: The Atlas Thread

Postby kernel65 » Fri Mar 20, 2015 3:10 pm

Thanks for the information. The measurements came in handy to verify what I am working with.

I think I will crack open the old drive and see what went wrong and keep it for parts. I read an old post on how to disassemble the drive and will go from there.

Thanks again!

Scott
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1965 Norton Atlas
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Re: The Atlas Thread

Postby Possum » Tue Apr 18, 2017 8:54 pm

Is there a drive ratio difference between a speedo drive gearbox for an 18" rear wheel and a speedo drive gearbox for an 19" rear wheel?

If so, what is the Part No. for a speedo drive gearbox for an 18" rear wheel?

And, what is the correct drive ratio? eg. 2:1 or 12/15 (1.25:1) drive ratio

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Re: The Atlas Thread

Postby Rohan » Wed Apr 19, 2017 1:16 am

Possum wrote:Is there a drive ratio difference between a speedo drive gearbox for an 18" rear wheel and a speedo drive gearbox for an 19" rear wheel?


No.
Or they would be in the parts books.

And how could there be, the difference is only fractional.
If you measure the rolling diam of 18" and 19" tyres, there is very little difference,
a 4.00 x 18 and a 3.50 x 19 are not too far different at all..

All you have a choice of is the one in the Atlas/dommie parts book 2:1 P/N 22888
https://andover-norton.co.uk/en/shop-details/17341
http://www.rgmnorton.co.uk/dept/instrum ... d01124.htm

The Commando uses the 15:12 ones, and different speedos.

I'm sure there will be more complexity to it, there always is.
Like c/w and anticlock rotations...
hth

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Re: The Atlas Thread

Postby frankdamp » Wed Apr 19, 2017 7:07 am

When the two prototype Commandos were built, they got speedo drives that weren't the correct ones. For some screwball reason, the Commando instruments were calibrated for drives with (I think) half the number of cable rpm/mph compared to the Atlas. It was a three months or more before we got the correct ones and we had to rely on the tachometer for speed indications. The speedo went off scale high at 50 mph.
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Re: The Atlas Thread

Postby kernel65 » Wed Apr 19, 2017 9:37 am

Just make sure you have the proper top hat spacer that fits the axel in a 2:1 drive ratio and it should work given you're using the original clock.
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Re: The Atlas Thread

Postby texasSlick » Wed Apr 19, 2017 9:58 am

kernel65 wrote:Just make sure you have the proper top hat spacer that fits the axel in a 2:1 drive ratio and it should work given you're using the original clock.


Agree!

Thanks to Time Warp who made me a top hat spacer so I could adapt a NOS 2:1 drive to my axle. Works fine.

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