Output flange bolts: torque?

[John Roberts]

I've just got hold of the special spanner for the above job: BMW Special Tool No. 00.2.560.

It's a simple enough thing, just a short ring spanner that is slim enough to get at the stretch bolts on the output flange, you can't get a normal socket on to them because there's not enough room for one or the ratchet or tommy bar or whatever. The other end has the usual half-inch (or perhaps three-eighths) socket for your torque wrench to fit into.

As it is possible to attach the torque wrench in more than one way to the special tool the actual torque put on the bolts can vary for any given reading on the wrench because the distances A and B (that is, the leverage) in the diagram are different, suppose the reading is 40 Newton Metres in both cases, but the bolt in case B will have 20% roughly more torque than in case A. They give a warning in Haynes regarding the changed torque on the bolt, but there is no mention of how the spanner should be aligned.

My guess is that it should both be in line, but it's only a guess, I could be out by 20%.

So how should it be?

 

[Rob Farmer]

Ring spanner twatted with a hammer works well for me. I guess there'd be a 20% difference between tight and f'in tight

 

[cookie]

i asked the same question here last year, and a long discussion ensued.

you'll have to do a search, 'cos i can't remember what the answer was now

 

[Kenny]

Forget the torquing down...just tighten them up as tight as you can, they are stretch bolts and won't come loose !! (Done loads and never had any problem - then again most are in the scrap yard now )

The ring spanner for the job is in the original toolkit in case anyone else enquires

Your nearly there now John !!

 

[cookie]

if they are really stretch bolts, how come...

there's no angular torque setting?

they don't feel like stretch bolts when you do them up?


i'm just wondering. you're not the first person to declare them stretch bolts. i have my doubts that they are any more stretch bolts than any other high tensile bolt

 

[MattW]

if they are really stretch bolts, how come...

there's no angular torque setting?

they don't feel like stretch bolts when you do them up?


i'm just wondering. you're not the first person to declare them stretch bolts. i have my doubts that they are any more stretch bolts than any other high tensile bolt

I guess they might still be stretch bolts but as they've got such a short 'stretchable' free length they'll feel a lot different to something like a head stud which has plenty of stretchable bolt?

 

[Steptoe]

The torque setting i use is FT ( fecking tight). Torque applied with a short scaffold tube on a 10mm ring spanner. As the spanner starts to bend, stop tightening.

I've re-used the bolts for as long as i can remember without any problems. The early models had a split/locking washer to be used with the bolt. The later models don't bother with it. .

 

[Magwych]

4o Nm is about 30 ft lb. So on a 6" spanner that would be a force of 60 lb/ 27 Kilo or effin' tight, depending on how you measure. On my old airheads that was about as much pain as I could take on teh palm using my ring spanner.

Not one came loose over 250 k miles of despatch riding; unless I undid it to disconnect the shaft .

 

[John Roberts]

i asked the same question here last year, and a long discussion ensued.

you'll have to do a search, 'cos i can't remember what the answer was now

Got it, eventually, you posted it on 18-11-09:
http://www.ukgser.com/forums/showthread.php?p=2101693&highlight=bolts#post2101693