Author Topic: ATD and Frankenstein nut  (Read 632 times)

Offline PDMiller

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ATD and Frankenstein nut
« on: 02.03. 2019 18:29 »
In an effort to stop my rebuild costs exceeding those of Bluebird I thought I might save a few quid and use the ATD to drive the tacho gearbox. I plan to convert the mag to manual and disable the ATD to stop it advancing. I guess the drive to the gearbox is then by a "Frankenstein nut"  My questions are: Does anyone have a picture or drawing of the nut, why is it called a Frankenstein nut and how do I separate the original nut from the ATD?
Any advice and comments much appreciated.
Thanks
Pete
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Offline Swarfcut

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Re: ATD and Frankenstein nut
« Reply #1 on: 02.03. 2019 19:27 »
Hi Pete....Welcome to the World of Theoretical Physics.  The ATD retaining bolt simply unscrews from the unit   (dream on)...it has a left hand thread, the so called self extracting mechanism, but they are usually reluctant to come out...like I say, theoretical.  Disabling the ATD is usually done by tack welding it up, but this is a bit of a one way trip, so only do it if the ATD is well worn and knackered, they still have some  good residual  value.

 Better to treat yourself to a new or used quality (?) fixed drive gear and a new retaining bolt.

 The Frankenstein Nuts I have seen were cheapskate homespun drive tags welded to the standard retaining bolt, a bit ugly, hence the name. If a genuine part exists, it  will be a bit of a search.

   No doubt Julian will be along soon, to shoot me down in flames. Probably got the left hand and right hand threads confused.

 Swarfy.
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Offline PDMiller

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Re: ATD and Frankenstein nut
« Reply #2 on: 02.03. 2019 20:26 »
You're probably right Swarfy, the £40 for a drive pinion pales into insignificance compared to the ever spiraling cost of the rebuild. It's a bit daft because in the 10 years that I've owned my Hinkley Bonneville I've probably looked at the rev counter three times but on the A10  it just looks the part and the gearbox drive appeals to my warped sense of what looks good.
The other thing that's a bit of a saga is finding a cable to fit the Indian tacho. The thread is 18mm x 1.5 Someone must sell them , I'll just have to keep looking.
Thinking of drilling a couple of small holes in the radial pieces of the ATD (that move apart when advancing) and wiring them together so that it's not  permanent.
If I can get the nut out of the ATU I'll make a new one to suit the tacho gearbox.
I thought retirement was going to be all feet up and panatellas but it keeps the old grey matter ticking over.
Cheers
Pete
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Offline duTch

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Re: ATD and Frankenstein nut
« Reply #3 on: 02.03. 2019 20:49 »

 I agree that it could be  a can o' worms, but for what it's worth if I recall to get the nut out, you need to undo from the armature as per normal which then pulls the ATD, and once free from the armature apply light outward pressure to the nut and turn it the other way to engage the Left Hand Thread and keep turning....I think
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Re: ATD and Frankenstein nut
« Reply #4 on: 02.03. 2019 21:49 »
G'day Pete.
A quick search finds a nut.
https://tinyurl.com/yxtw52zr
And the pinion.
https://tinyurl.com/yyk8guy5
But I'd try Andrew at Priory Magnetos first
https://sites.google.com/site/priorymagnetos/home
Cheers
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Offline Swarfcut

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Re: ATD and Frankenstein nut
« Reply #5 on: 02.03. 2019 23:07 »
Pete.. There you are... Thanks to esteemed members  duTch and Musky.   All you need.... and a choice.......you lucky fella!

Nicely done, Guys.

Lateral thinking to wire it up-never thought of that!


 
Swarfy.
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Offline PDMiller

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Re: ATD and Frankenstein nut
« Reply #6 on: 03.03. 2019 08:36 »
What a team. I wonder how long it would take the forum to sort Brexit. 😯. Thanks lads.
The man cave beckons 😎
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Offline Swarfcut

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Re: ATD and Frankenstein nut
« Reply #7 on: 04.03. 2019 20:45 »
Pete, The more I think about it a bike with an ATD would be unlikely to have a Tacho driven by the maggy, only the more sporting variants with manual mags would be so fitted.

 So an official part which combines a ATD bolt and drive tags is unlikely, except as a custom mod. Hence the backyard Franky weldup.

 The bolts suggested  by Musky are only suitable for  fixed drive gear mags with manual advance.

 Swarfy.
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Re: ATD and Frankenstein nut
« Reply #8 on: 05.03. 2019 01:15 »
Yes Swarfy you are right. The drag on the nut by the tacho drive would upset the auto unit. I thought Pete was going for a manual and was going to lock the ATD and save a few $ by altering the nut.
Cheers
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Offline PDMiller

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Re: ATD and Frankenstein nut
« Reply #9 on: 05.03. 2019 08:48 »
Yes it's the wired up ATD and manual AR for me  :!  maybe.. I planned to make a custom nut ,left hand thread and all but failed miserably to remove the nut from the ATD . Guess the left hand thread must be burred over with years of use. I eventually locked the nut in place using a 3/8 BSF stud gripped in the lathe so I could drill the head deep enough to mount an adapter to drive the tacho gearbox.  I'll post a pic next time i'm in the garage just for people to giggle at but now I'm having second thoughts.
If the weakened head snaps off or the adapter comes adrift I could have a horror story of Groily's proportions to report. Then if the contraption is a couple of thou off centre it would wreck the bearings in the very expensive tacho gearbox.
The answer is obvious: BUY THE RIGHT BITS. TIGHT FISTED B~&&£r. *eek*
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Online Black Sheep

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Re: ATD and Frankenstein nut
« Reply #10 on: 05.03. 2019 14:29 »
Ah yes, one reason the ATD has fibre teeth is that should the mag lock up you only lose a few fibre teeth rather than something more catastrophic occurring. Always an exciting if remote possibility with a solid alloy pinion.
The correct mag pinion for a manual mag isn't really that expensive...
The reason I opted for a manual mag on the Star Twin was to be able to go full advance early to get a bit more grunt on steep trials sections. It does work. 
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Offline PDMiller

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Re: ATD and Frankenstein nut
« Reply #11 on: 05.03. 2019 18:13 »
The Jury is out but this might be confined to history, filed under "Almost Ran". It would probably be OK but maybe not worth the worry?
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Offline UncleD

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Re: ATD and Frankenstein nut
« Reply #12 on: 16.03. 2019 04:43 »
The other thing that's a bit of a saga is finding a cable to fit the Indian tacho.

I have had excellent service (and price) on custom cables from this mob.

http://vintagebritishcables.com/Smiths-Speedometer-Cable-SmithsTachometer-Cable.php
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Offline PDMiller

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Re: ATD and Frankenstein nut
« Reply #13 on: 24.03. 2019 18:55 »
Carrot Cycles keep the cables and will supply the nuts and the cable end ferrules to fit the Indian ( and probably any other ) speedo. With their fittings I was able to cobble together speedo and tacho cables. I think they will make cables with any combination of fittings so a handy name to remember.
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