Ask an Engineer

[bogan]

With Easyflow or similar you'd make most of the length of the joint about 0.05mm clearance, with perhaps the centre 4mm of the pin size for size. Tin the pin and cam bores, lay it into a simple jig to keep it aligned and timed, heat it up to about 650c and push the lot firmly together. As long as the surfaces are tinned properly that won't move, but it takes a mere 10 minutes to cross drill and ream the assembly and fit taper pins.

Editedit: You could probably use the same technique with the appropriate loctite instead of solder.

With loctite would you get away with a smaller clearance? I'm just thinking the jig would difficult to make, so if we could get away with just fitting it together and pinning it that would be awesome.

[pete376403]

Can cast iron be silver soldered? (easyflow/silfos are the only two I learned of, but that was a long time ago)

[Ocean1]

With loctite would you get away with a smaller clearance? I'm just thinking the jig would difficult to make, so if we could get away with just fitting it together and pinning it that would be awesome.

Yes. Less secure but probably OK, and you don't have issues with the heat distorting shit or damagine hardening. I'd look at the cam joint prep wall thickness as the weak point, make the pin a couple of mm smaller to compensate. And make sure the bottom of the bore is radiused. Think the shaft OD was 24mm nom? What size is the existing hole down the shaft?

Loctite 640 (iirc) is for high temp close tolerance applications. Needs to be oil resistant too, check if it's been superseeded. You'd have to research clearances but I suspect you'd get away with as little as 0.005mm. Guess you could dummy assemble it, set the timing up right and then drill and ream for taper pins before taking the lot apart to clean and glue. I'd cut the pins 1mm proud on the minor dia side and csk that side of the hole very slightly, so you can carefully peen the pin after it's well tapped home.

How critical is the journal to journal pitch, are you going to get away with losing the thickness of the cut, (1.5mm?) or do you need two doner cams?

[Ocean1]

Can cast iron be silver soldered? (easyflow/silfos are the only two I learned of, but that was a long time ago)

I've had trouble with shit grey iron, heaps of free graphite, but I think you'd be OK with anything they'd make a cam out of.

[ducatilover]

Yes. Less secure but probably OK, and you don't have issues with the heat distorting shit or damagine hardening. I'd look at the cam joint prep wall thickness as the weak point, make the pin a couple of mm smaller to compensate. And make sure the bottom of the bore is radiused. Think the shaft OD was 24mm nom? What size is the existing hole down the shaft?

Loctite 640 (iirc) is for high temp close tolerance applications. Needs to be oil resistant too, check if it's been superseeded. You'd have to research clearances but I suspect you'd get away with as little as 0.005mm. Guess you could dummy assemble it, set the timing up right and then drill and ream for taper pins before taking the lot apart to clean and glue. I'd cut the pins 1mm proud on the minor dia side and csk that side of the hole very slightly, so you can carefully peen the pin after it's well tapped home.

How critical is the journal to journal pitch, are you going to get away with losing the thickness of the cut, (1.5mm?) or do you need two doner cams?

The first two paragraphs are a wee bit above me...

I hadn't actually considered the cut. I think there's a tiny bit of room to play with, but I personally wouldn't try much
I suppose some sort of spacer may be needed? If I had, say, 2mm taken with the cut and run a 2mm spacer in it?

[Canis G.]

Is there a reason why stainless exaust studs are not used on bikes (I am thinking air-cooled here)? Seems it would make it a damn site easier to remove exausts etc instead of dealing with gunged up steel ones.

Cheers for your patience.

[bogan]

Is there a reason why stainless exaust studs are not used on bikes (I am thinking air-cooled here)? Seems it would make it a damn site easier to remove exausts etc instead of dealing with gunged up steel ones.

Cheers for your patience.

Stainless has more potential to corrode inside the aluminium head. They just went with the lesser of two evils and kept the corrosion on the outside. Though cost is probably a factor too.

[Ocean1]

It also cold-welds to itself, you have trouble with nuts siezing onto bolts with SS unless you use the right lubricants. It's also not as strong, (generally) as most modern fasteners materials. Having said that I've never been happy with the common OE practice of using cadnium plated screws in alloy cases, and I've used SS replacements before now.

Edit: good thread lubricant and general all-round corrosion preventitive is Prolan, (lanolin) available from most fasteners suppliers.

[carburator]

Stainless has more potential to corrode inside the aluminium head. They just went with the lesser of two evils and kept the corrosion on the outside. Though cost is probably a factor too.

thermal exspanion properties..
get liberal with copper or zinc or never seaise and no issues or either happening..
however i did use copper washers and brass nuts ( lockwired ) on a mainfold that
we would take on and off a lot ( racing )

[imdying]

How about Ti studs? If you had a bike with Ti exhaust studs, what sort of nuts would you use on them?

[carburator]

How about Ti studs? If you had a bike with Ti exhaust studs, what sort of nuts would you use on them?

Ti is a pain in the ass more so for heat cycles, Inconel studs if you really need the strenght factor, however over the
years ( lost count ) how many Ive drilled out on LPT cases is not funny and after a couple of heat cycles are hard MO Fo's
to drill out if snapped off..

end of the day MS ( mild steel ) zinc plated work well for non turbo applications.. or anything really..

[schrodingers cat]

end of the day MS ( mild steel ) zinc plated work well for non turbo applications.. or anything really..

Regular maintanence? It will never catch on

[Ocean1]

How about Ti studs? If you had a bike with Ti exhaust studs, what sort of nuts would you use on them?

Depends. Why are the studs Ti? Is the extra tensile strength needed? If not I'd get rid of them, it's almost impossible to predict service duty cycles for it, they might crack any time.

I'd look at AB2 nuts at a full dia length, (8mm long for an M8 thread) for Ti exhause studs. If they wern't up to the strength requirements then I'd probably get rid of the Ti studs anyway and uprate the thread size.

Edit: Sorry, AB2 is an aluminium bronze alloy.

[Ocean1]

Ti is a pain in the ass more so for heat cycles, Inconel studs if you really need the strenght factor, however over the
years ( lost count ) how many Ive drilled out on LPT cases is not funny and after a couple of heat cycles are hard MO Fo's
to drill out if snapped off..

end of the day MS ( mild steel ) zinc plated work well for non turbo applications.. or anything really..

Oversizing studs has an advantage beyond reducing the requirement for high-strung materials, you can pre-drill a 2-3mm hole up the full length. You've got surplus CSA anyway, and it makes drilling the wee fuckers out SO much easier of they fail.

PS, anyone seen LH drills for sale recently? I've managed to fuck most of my limited supply.

[pete-blen]

Right you clever buggers
Question/scenario thing

I have a plan, change my firing order to a "medium bang" set up.
Current is a typical flat plane crank (ZZR600D), waste spark and carbs
What I'm planning: 1&4 fire together, then 2/3 as normal.
So it'd be 1/4-2-nothing-3, repeat.

Reason, coz I want to.

The best idea I have seen so far has been the #4 lobes off, machine down the cam shaft then put it back together with the new timing by press fitting the two parts in a sleeve. (like an RC30 cam)

Now...
How tight am I wanting the sleeve,
Slightly smaller I/D than the O/D of the cam? Then heat it...lots...and press 'em together (in a jig to get timing right)

I also considered vaing a small keyway in the cam and sleeve to allign it, but I'm concerned it may weaken the sleeve.

Help an idiot out, for a choccy fush.

I've been chatting to Bogan about it, but he hates 4cyls, so he's probably wanting me to do it and explode my motor so I have to buy another Bros650...

I'm also aware that the added effort to turn 1/4 over on the cimp stroke may be detrimental to the starter...or it may simply not have enough juice to turn over.

Been there done that... made a GSXR750 think it was a twin...
for one of my TQ midgets...
Cut the cams turn one end 180* re-weld back togeather..
change the plug leads..
just don't try to rev it it 11,000 rpm... set the red line about 7500/8000
and make use of the massive torque it will gain..

Gavin Sendle/Craig Webby won the NZ speedway side car champs with a
GSXR1100 running as a twin..