Sleeve gear bush material

[Slymo]

Had an unfortunate experience using an off the shelf bronze bush from a local bearing provider in my A10 box. It lasted about six months before I found the noise suspicious and pulled the box apart again. The bush I had made had literally squished out front and back of the sleeve gear making the clutch wobble up and down in a very distressing fashion. I had a spare sleeve gear with a used but serviceable bush in it and the bike has been fine since. I'm keen though to sort out the one that was in there but obviously need to know exactly what sort of alloy I'm after for the bush. Anyone able to provide an answer or point me at a supplier?

[KiwiGF]

It’s 6 pages this has some useful info.

My newly fitted sleeve gear bushes failed quickly first time around, but I am still not 100% sure why  but the rep,acements have been ok for getting up to 9000 miles now tho, despite a belt drive being fitted (albeit I am not sure “tension” in the belt accelerates wear…..yet)

https://www.a7a10.net/forum/index.php?topic=5202.75

I used a cheap hone designed for brake slave cylinders to get the clearance on the new bushes from draganfly, the second time around.

[Slymo]

Read all six entertaining pages but didn’t see an answer to my question other that the Gunmetal reference on page six. Searching the WWW I found an English firm: https://www.rightonblackburns.co.uk/news/guide-to-bronze-sleeve-bearings that gives an excellent description of the various types and applications of bronze bushing materials and their various strengths and weaknesses. I’ve emailed them and in the event they respond I’ll post the result here. In my case there was no oil starvation and no excessive primary tightness, just a very soft alloy that literally squished out either end of the sleeve gear. It took around 6 months of regular use but was clearly a product failure.

[trevinoz]

I think that the material I used was leaded gunmetal, LG1 from memory.
Check out Fraser Bronze, an Aussie mob but have branches in N.Z.

[Slymo]

Excellent will look them up. Cheers :)

[Brian]

Even if the material used was not "correct" for the job I dont think it should have failed like it has. Being a "off the shelf" item it was probably  phosphor bronze which is more than capable. A couple of things to check, when you fitted it did you ensure the three radial oil supply holes lined up ? Another is possibly the primary chain being too tight.

[Swarfcut]

 Original design is two bushes, a plain bush outboard, and an inner, drilled bush. This is relieved on the ID where it joins the outer bush to provide a small reservoir for oil, providing lubricant as the mainshaft rotates at a different speed to the sleeve gear in the intermediate gears. In top gear mainshaft and sleeve gear rotate as one.
 
  Most originals I have seen were steel backed split tube type bushes, with a thin layer of bearing metal as a facing.  A single solid bush still needs the gap in the middle  and the three oil holes. There's probably a name for this type of composite bush, also seen on car front suspension units where the damper rod moves into the strut body.

 Swarfy.

[RDfella]

Most originals I have seen were steel backed split tube type bushes, with a thin layer of bearing metal as a facing. 

As Swarfy says, made in the same way as automotive small-end bushes etc.
Bronze is a metallurgy issue all of its own. There's hundreds of different bronze alloys to suit many different purposes - the details given in the link to Blackburns gave some idea of the scope. I note they didn't mention two very popular bronzes - Phosphor and Silicon (the latter widely used in marine application). High performance propellers are usually Nickel Aluminium Bronze - extremely strong but a pig to machine.
Maybe the bush that failed was Oilite? That's a sintered bronze loaded with oil and can crumble if abused. Ideal for situations where lubrication is required but cannot be provided. The bronze most firms will have in stock is Phosphor, usually in hollow bar form ready for machining to size.
   

[Slymo]

1.No not sintered bronze it was a plain bronze bush off the shelf at A&E Bearings. 2. All oil ways were drilled and appropriately positioned and a recess was machined in the middle of the bush as per the original. 3. The fit was around .002" clearance and there was no sign of tightening or galling. Also there was almost no sign of bronze in the gearbox oil. Finally the bush was machined so that there was nothing poking out of either end of the sleeve gear however on removal there was a protrusion of around .040" from the output side and .015" to .020" from the inside. The bush as stated had simply squished out.

[Slymo]

Alllllsoooo! I have a couple of spare sleeve gears in very nice condition gear and dog wise but both without bushing. Thought I may as well sort both while I’m at it and discovered that both of them have the smaller ID than usual 15/6” spec. Both of them have a hole 29/32” (906.5 thou). Can’t see a reference to this anomaly anywhere in the literature but two in my collection of three clearly mean that it isn’t that unusual. I’m guessing it’s an earlier Plunger box feature but as they are otherwise identical I’ll try not to lose sleep over it.

[chaterlea25]

Hi All,
The squishy bush may have been SAE660
it is coppery in colour compared to LG1 or PB1
SAE 660 is quite soft by comparison??
I was recommended this to make a split big end bearing for an early Blackburne engine, on this the con rod has a flat plate at the end of the rod and the 2 halves of the bush bolt to this
Test fitting and tightening the bolts squashed the bronze every time
I got it sorted eventually

John

[BSA_54A10]

I use LG2 or 85:5:5:5 for just about every bush
Not the asolute best in every application but it makes by workshop inventory easier
Phos bronze is too hard
You want the bust to wear, not the shaft
However a big problem is main shafts that are oval or even bent
I went through all that I have here and not a single one was both strait & round so I have been doing a bit of press work to true one up good enough to fit .