RH vs LH threads

[Nick WheelerParticipant @nickwheeler]

Posted by Hopper on 14/03/2021 11:28:33:

Posted by Nicholas Wheeler 1 on 14/03/2021 10:55:27:

Posted by SillyOldDuffer on 14/03/2021 10:09:27:PS. Reading the book, which is about values and the 'Metaphysics of Quality', I found the first half delightfully readable but the second half blew my mental fusebox. It plunges deep into the meaning of 'quality' and is too hard for me: I'd be grateful If anyone can explain part two in simple terms!

It's utter drivel.

Is that simple enough?

Either that or you don't understand it. Bit like the Romantic with the left hand thread that SOD mentioned.

I had the same thing when we studied metaphysics at school: it turned out to be a very complicated way of describing/explaining simple things, with little improvement for the effort.

[Bill PhinnParticipant @billphinn90025]

Posted by John MC on 14/03/2021 09:02:24:

A few days I had a "zoom" get together with a few cycling friends. One topic of discussion was why do bicycles use left-hand threads in certain places? I let my friends discuss this then jumped in with the right answer.

In case it's not already been mentioned, the reason has to do with what's termed hypocyclic fretting precession.

[Grindstone CowboyParticipant @grindstonecowboy]

Way back in the 1960s, my dad had a Plymouth car with LH threaded wheelnuts on one side. The local garage stripped one the first time they tried to take a wheel off, so they made a tap and a new nut in their workshop – I doubt many garages would or could do that these days. They gave him the tap, which I still have. Not sure if the stud was undamaged or if that was remanufactured as well.

Rob

[not done it yetParticipant @notdoneityet]

My Bedford TK has both threads on the wheel nuts (not on the same nut!).

[old martParticipant @oldmart]

Years ago, I bought a Ballistic full suspension mountain bike frame. The bottom bracket had been welded on the wrong way round and on my first ride one side of the bottom bracket came loose. Fortunately I had self extracting bolts in the cranks and could tighten the bottom bracket enough to ride home. The bottom bracket, a Shimano XTR was treated to a little threadlock and gave no more trouble. Having right and lefthand threads counteracts the rolling forces which are present in bicycle cranks.

I believe that Italian bicycle bottom brackets have righthand threads both sides, so they may have a method of keeping them tight.

[Andy StopfordParticipant @andystopford50521]

Zen and the Art of Motorcycle Maintenance?

Too much Zen, and not enough motorcycle maintenance, I thought when I read it as a teenager.

And he completely blew it for me when he's doing an oil-change and just lets the old oil run out onto the ground.

Quality, Robert, quality.

[egaParticipant @ega]

Posted by old mart on 14/03/2021 15:15:35:

…

I believe that Italian bicycle bottom brackets have righthand threads both sides, so they may have a method of keeping them tight.

Traditionally, Italian (and French) fixed (RH) cups were indeed right hand threaded and, hence, were very firmly tightened when installed to prevent loosening in use. Left hand threaded cups were, presumably, self tightening and in consequence either kind are difficult to remove.

The subject is well covered by the Sheldon Brown website where, in particular, a DIY removal tool is described. The French call this kind of tool a "bloc-cuvette", literally a cup tightener but the phrase apparently also refers to the clip-on WC bowl cleaner!

[not done it yetParticipant @notdoneityet]

Pedal bikes have clock- and anti-clockwise threaded pedals for a good reason?

[peter smith 5Participant @petersmith5]

And don’t forget that fittings on oxyacetylene are right handed for oxygen and left handed for computable gases

. Note the notch cut on the corners of the nuts to denote LH thread.

pete

[John MCParticipant @johnmc39344]

I thought it time to ressurrect this thread. The choice of LH vs RH threads on a bicycle is done for good reason. Considering the pedals, RH thread on RH side, the often made assumption is that the pedal rotates CW on this side , it doesn't, it rotates ACW, the direction that will undo a RH thread. So why the RH thread?

A couple of the replies to my original question have "got it", what I am looking for is a simple explanation. So, once again over to you guys.

John

[Nick Clarke 3Participant @nickclarke3]

Posted by John MC on 29/03/2021 09:27:05:

I thought it time to ressurrect this thread. The choice of LH vs RH threads on a bicycle is done for good reason. Considering the pedals, RH thread on RH side, the often made assumption is that the pedal rotates CW on this side , it doesn't, it rotates ACW, the direction that will undo a RH thread. So why the RH thread?

A couple of the replies to my original question have "got it", what I am looking for is a simple explanation. So, once again over to you guys.

John

A pedal will indeed turn anti clockwise on its spindle, however the spindle is not totally frictionless so the force of a power stroke from the rider will tend to tighten it in the crank surely?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi John MC, here's my crude diagram of how I understand it. Notice the drag force on the pedal spindle is in the opposite direction to the resistance force, the resistance force is the resistance the road wheel has from turning, therefore a left hand thread on the pedal spindle will tend to tighten.

Regards Nick.

P.S.  If the pedal seizes onto the spindle you will find the pedal may well unscrew if it isn't rusted in, which has happen to me at least once, but I was young enough then to get home on one pedal.

Edited By Nicholas Farr on 29/03/2021 11:00:08

[old martParticipant @oldmart]

Posted by Bill Phinn on 14/03/2021 13:12:05:

Posted by John MC on 14/03/2021 09:02:24:

A few days I had a "zoom" get together with a few cycling friends. One topic of discussion was why do bicycles use left-hand threads in certain places? I let my friends discuss this then jumped in with the right answer.

In case it's not already been mentioned, the reason has to do with what's termed hypocyclic fretting precession.

I dont think anyone paid any attention to your answer, or understood its meaning.

[Andy_GParticipant @andy_g]

Posted by old mart on 29/03/2021 19:00:26:

I dont think anyone paid any attention to your answer, or understood its meaning.

It's still the right answer though.

[Martin KyteParticipant @martinkyte99762]

Posted by Bill Phinn on 14/03/2021 13:12:05:

Posted by John MC on 14/03/2021 09:02:24:

A few days I had a "zoom" get together with a few cycling friends. One topic of discussion was why do bicycles use left-hand threads in certain places? I let my friends discuss this then jumped in with the right answer.

In case it's not already been mentioned, the reason has to do with what's termed hypocyclic fretting precession.

That's a little like the bloke who went to the doctor complaining of an itchy arse. Ah said the doctor you have a bad case of Scabrosa Asinum. What's that said the bloke. Err . . . . it means itchy arse in Latin replied the doctor. Huh said the bloke I came here for a diagnosis not a translation, I already know what to call it I just want to know what causes it.

:O)

regards Martin

[Bill PudneyParticipant @billpudney37759]

I read The Book in the mid 70s, it seemed appropriate at the time. I am a technical person and have been all my life, I also understand the need for beautiful things, and beautiful design. F'instance, for me a 1957 Grand Prix Moto Guzzi 500cc is just about the epitome of pragmatic, elegant design. Of course there are examples wherever you look, but for me that 'Guzzi is perfect!!

cheers

Bill

[HopperParticipant @hopper]

Posted by Bill Pudney on 30/03/2021 00:14:13:

I read The Book in the mid 70s, it seemed appropriate at the time. I am a technical person and have been all my life, I also understand the need for beautiful things, and beautiful design. F'instance, for me a 1957 Grand Prix Moto Guzzi 500cc is just about the epitome of pragmatic, elegant design. Of course there are examples wherever you look, but for me that 'Guzzi is perfect!!

cheers

Bill

Pragmatic and elegant down the straights. Not so much so on the corners. I'll take a Manx thanks. Elegant in its simplicity, straight or corner.

[Gerard O’TooleParticipant @gerardotoole60348]

Posted by Andy Stopford on 15/03/2021 12:14:40:

Zen and the Art of Motorcycle Maintenance?

Too much Zen, and not enough motorcycle maintenance, I thought when I read it as a teenager.

And he completely blew it for me when he's doing an oil-change and just lets the old oil run out onto the ground.

Quality, Robert, quality.

I Think Pirzig addresses that in the very first page of the introduction/preface when he writes

"it should in no way be associated with that great body of factual information relating to orthodox Zen Buddhist practice. It's not very factual on motorcycles, either"

[Bill PudneyParticipant @billpudney37759]

Sorry I mean't to say the single cylinder one, not the V8!! The V8 was certainly an amazing design, but for me the single is so beautiful!!

cheers again

Bill

[John HaineParticipant @johnhaine32865]

Posted by John MC on 29/03/2021 09:27:05:

I thought it time to ressurrect this thread. The choice of LH vs RH threads on a bicycle is done for good reason. Considering the pedals, RH thread on RH side, the often made assumption is that the pedal rotates CW on this side , it doesn't, it rotates ACW, the direction that will undo a RH thread. So why the RH thread?

A couple of the replies to my original question have "got it", what I am looking for is a simple explanation. So, once again over to you guys.

John

So you can put a spanner on the flats on the pedal, with the pedal horizontal and facing forward, so the spanner handle is near the bottom bracket. Then stand on the handle to exert maximum torque to undo while holding the bike down and back firmly.

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