Rockerbox studs and nuts and bolts in general

[duTch]

Bugga!
   
I had intended to start this about something to do with shims but lost the plot!! so did this instead.

  While searching the free googley net for specs on rocker box studs a while back I came across a couple year old discussion about rocker box leaks and other stuff but now can't find it so am starting again.

    I recall maybe Rocket racer? or Road Rocket? posting about socket caps , and Muskrat -in out,in out? I know that sounds dodgy, but that's the words I remember -sorry, and Beezas Bill,Macc and or Bob?

   I have used socket caps instead of the standard double ended studs because either I didn't have the correct ones, or they were trashed, or socket caps seemed easy to use,not just in the rocker box but crankcases, and any where there is a joint too.
      Somewhere it occurred to me that the double ended studs are like that for a reason  (maybe I'm just getting older)
 in particular the ones with coarse thread one end, fine the other.
  I'm probably stating the obvious here, but it seemed reasonable that the fine thread will not only cope with vibration better, but also give a tighter, more controlled and even torque for less effort, which I figure is better for sealing oil tight joints, as opposed to the whitworth thread .
   
      Yes I agree with Rocket(R-box hard to get on/off- studs hard to get in/out?) and Musky(constant out/in will wear them?) both with what ever they said, but in essence I reckon advantageous (circumstances permitting)to utilise the studs coarse thread for case retention and the fine thread for the tighten/loosen action, even if it means loosen/tighten using fine thread(nut) and maybe add a locknut to remove/replace stud for personal convenience?
 

Could be wrong but,Beeza Bill,Macc or Bob (?) mentioned replacing Stainless with regular steel in cases?? just am wondering the background on that, I imagine electrolytic action ?

Also I did a dummy run on that rear bottom r-box long nut -potential bitch! oh yeah I was supplied with those, a couple of snug fitting spring washers-is that it?? never had those before

   'nuff for now, comments welcome -got it out there, but saturday night, need food that I didn't find last night- will get back on re shims later
 

    From duTch 

[Goldy]

Dutch. You are exactly right in what you say. The course thread gives good anchorage into the soft aluminium alloy and the fine thread gives better vibration resistance and torques up better. Stainless bolts can produce what is called galling but that is usually stainless nuts on stainless threads and will then be difficult to remove. Rocker box fasteners can be plain steel as they are not in a position to corrode and also cannot be seen. all the best Goldy

[muskrat]

 Always use anti seize on ss bolts with ss nuts. Studs are good locaters and a stud will take a lot longer to wear the thread than a bolt going in and out of alloy. Beats me why they went to fine threads in alloy on the A65's
Cheers

[bsa-bill]

Hi Dutch
The benefit of using studs is that should one get stripped it is easily repaired by replacement, whereas a stripped thread in he rocker box casting means drilling out the old thread and using one of a variety of insert.
It could be said of course that this is no big job these days, however there is also a good chance that if to much tension is used on a socket cap not only will you strip the thread in the rocker box but more than likely crack the corner of the box as well.
The coarse thread on the stud screws into the alloy box as is standard practise in alloy, the fine thread will be the first to strip if the box is overtightened so act in a sort of sacrificial way.
I've not had any issue with using stainless in alloy, perhaps after it's been in for a half century it might be an issue though , on the other hand stainless threads should always be lubricated before using and I'm sure there is a lubricant that will prevent corrosion .
Re the rear nuts, I did have a problem with these, the cause was that Draganfly supplied wrong studs,  I did not pick up on the difference soon enough, the studs have as you say two threads, the fine thread should be longer than the coarse one, the ones I got were the other way around, consequently not all the coarse thread was within the rocker box but more important there was not enough of the fine thread to allow the long nut to pull the box down (it was thread bound before the box was down) a second washer would have cured this maybe ?????, I would recommend you check yours as there should be only one washer in there.
All the best - Bill

[duTch]

Good stuff, we're all on the same page, I know about the 'galling' and use nicklestuff/never seize,
Also,

the fine thread will be the first to strip if the box is overtightened so act in a sort of sacrificial way.

This is why I had to go the other way before as cycle threads were hard to find 'round here 30 yrs' ago, nuts of unknown quality could be procured from a bicycle shop then,but not studs ,but I went into same recently, maybe from curiosity (or perverse entertainment), and the guys looked at me kind of funny, like more funny than any other day -cycle thread??
  Bill yes I remember that part of the thread now, and checked mine, I think about 9/16 ww & 15mm+ cyc-no binding. I think it was that concern that made me research it and found the thread. can't recall now where I got the (Zn)studs, maybe Supreme Nuts& washers (+ other fancy stuff) came from Lightning Spares, the washer is nice fit but there's not a lot of ally material there(under hex) to seat on so'm a bit 'concerned' but is probably ok.
  Could ramble on but best not.  Thanks blokes -it's been bugging me for a bit but figured good to get it back out in the wind.

         cheers for now

[beezermacc]

A further point regarding fine and coarse threaded studs into aluminium. In nearly all circumstances a coarse thread is screwed into the aluminium up to the shoulder of the thread i.e the thread does not 'bottom out' to the base of the hole. When tightening a stud into aluminium, up to the shoulder, the shoulder acts as a taper lock onto the seat of the aluminium so it takes more force to remove it than it did to screw it home. If you were to use a fine thread in the same situation the greater leverage (almost x2 sometimes) would make it less obvious when the shoulder hits the aluminium (due to the more gradual travel rate) making it more like likely to shatter the aluminium component. Provided the fine threads are clean and free running the fine threads should release first when undoing a fitting of this type. This is also the reason why fitting a nylok or other self gripping nut to studs in alumium is not very good practice as this nearly always draws the whole stud out when unscrewing, so it is important to seperate the nut from the stud and screw the stud fully home during reassembly. End of lesson - sorry!

[bsa-bill]

the shoulder acts as a taper lock onto the seat of the aluminium so it takes more force to remove it than it did to screw it home.

Now that I did not know, Thanks Beezermacc

[duTch]

Thanks B-Macc, All points noted, I think that's what I had in mind with the 'locknut' idea in 'blind' situations like the rocker box that in some cases may necessitate removal of the stud to clear the head and protruding pushrods, loosening the fine thread first then add the lock nut to remove stud, and reverse procedure to replace stud then remove locknut and torque up with the fine thread. Noting though that this may not be possible with the rear r/box extended nuts!

 Cheers

[bsa-bill]

I and many others I think with alloy heads locktite the nut on that top rear rocker stud so that the stud does come out when removing the cover, in view of Beezermacc's info I'll perhaps counter sink the stud hole a little to make the stud easier to remove

[beezermacc]

The rear, upper, stud should have flats on its sides to enable removal with a spanner, that's why it has a different part no.

[Rocket Racer]

I'm currently using cap screws, primarily due to clearances fitting the rockerbox, but also for convenience.
The top ends been on and off a few times for unrelated maintenance and they have stood removal and refitting well.
I assemble them with low strength loctite.
I am however conscious I dont get the same pull down sensitivity as a fine stud thread and may consider trialing removable studs in future, but not a high priority at present.
I make no claims my rockerbox is weap free, but then this motor does not have an easy life.