Line boring ( Ariel Square Four was Parkerizing)

[nornet]

A picture is worth a thousand words especially with a twin crank engine.



Top View



Front View



New bearing to be machined



Other side of new bearing.

When the bike was built, there were about 4 bearing sizes available: std, +.20, +.40 and +.60. These could and probably were reamed to size. The only bearing available today is +.100. it would not be possible to ream this much.

The diameter of the unfinished bearing is about 1.1" and the depth of the bearing is about 1.1"

All the equipment I have seen in basically automotive shops is unsuitable as the blocks they are working on have a flat reference plane on the bottom.

 

[bitzz]

So you want to increase the ID of that bush by 0.100" ? There isn't enough babbitt.
You are going to have to remove the babbitt, increase the hole size, then repour the babbitt.

Then ream the babbitt to the shaft size(s) then press them into the cases.
No align boring necessary.

You can't bore babbitt, it is too soft. You scrape it with a knife or reamer.

 

[nornet]

Correct, I want to increase the size of the bearing by about .100". The more knowledgeable members of the vintage Ariel motorcycle club (AOMCC) in the UK have this work done in a shop that use the line boring process. There are a number of shops over there that can perform this but shipping is prohibitive.

I think they are boring these now because there is so much extra Babbitt that has to be removed. I will ask Gord Bush about this (he can't do the work as I mentioned previously). He certainly will know if it doable.​

You can view the AOMCC forums on their site without an ID.

Select the section "Four Stroke"

Search "line bore" or "line boring"

Scraping is an art I wouldn't even consider, I'd love to be able to pour Babbitt. John at Canadian Crank has some stories about old timers that were wizards.

 

[Delboy]

Hi. A co worker rebuilt a square 4 motor a few years ago. IMHO he buggered it up though as he built a bobber around it and ruined it. Anyway....

He said give Draganfly in the UK a call - +44 (0) 1986 894798.

He said they were able to supply him with larger diameter as his crankcases were worn and there was enough meat in them to size the ID for his crank. He just had a local precision machine shop fit them.

Brad at Steffan in Oshawa is a good guy and is always willing to provide advice

 

[nornet]

Hi. A co worker rebuilt a square 4 motor a few years ago. IMHO he buggered it up though as he built a bobber around it and ruined it. Anyway....

He said give Draganfly in the UK a call - +44 (0) 1986 894798.

He said they were able to supply him with larger diameter as his crankcases were worn and there was enough meat in them to size the ID for his crank. He just had a local precision machine shop fit them.

Brad at Steffan in Oshawa is a good guy and is always willing to provide advice

These bearings came from Draganfly. I won't tell you how much I've spent there over the past few years but its substantial. Fortunately the pound has gone down since Brexit.

Just to be clear, the OD of the bearings is fine, It's the ID that requires machining.

 

[J_F]

so there's a roller bearing on one end of the cranks
and a babbit bearing on the other?

concentric reaming of the babbit to proper ID
and assuming the cases bolt up properly with dowels
and the OD where the bearings go in is okay
things should be lined up pretty well?

can you torque the cases together and measure the OD's
where the bearings go in, to see if there is an alignment problem?
or maybe you've done this and know there is a problem?

 

[nornet]

so there's a roller bearing on one end of the cranks
and a babbit bearing on the other?

Correct

concentric reaming of the babbit to proper ID
and assuming the cases bolt up properly with dowels
and the OD where the bearings go in is okay
things should be lined up pretty well? There are 2 locating dowels. There is no alignment problem that I am aware of. The wear on the existing bearing is virtually zero. The reason it is being replaced is that it is the wrong bearing for the bike. I am maxed out on my attachments so I can't show you the incorrect bearing.


can you torque the cases together and measure the OD's
where the bearings go in, to see if there is an alignment problem?
or maybe you've done this and know there is a problem?

Is a site supporter allowed additional space for pics?

 

[TwistedKestrel]

Is a site supporter allowed additional space for pics?

You're better off uploading them somewhere else, like Tinypic or Imgur and then linking them. The forum storage for photos is very limited

 

[Delboy]

These bearings came from Draganfly. I won't tell you how much I've spent there over the past few years but its substantial. Fortunately the pound has gone down since Brexit.

Just to be clear, the OD of the bearings is fine, It's the ID that requires machining.

I can only imagine what they cost :-(

He had his done at a regular machine shop. They do machining for performance motors and heads for cars and bikes. Since your cases are in good condition i would think yours would be easier.

BTW. He said they were quality items.

I can ask him where his were done but you probably want somewhere local

 

[Tripletrouble]

Did you ever get ahold of Ken Rosevear? I know he has rebuilt several Square Fours.

 

[nornet]

Did you ever get ahold of Ken Rosevear? I know he has rebuilt several Square Fours.

I haven't talked to Ken yet, I recall you mentioning him several years back. I have several leads from an Ariel owners forum I'm also pursuing.

Thanks for the reminder.

 

[Rob Star]

All the equipment I have seen in basically automotive shops is unsuitable as the blocks they are working on have a flat reference plane on the bottom.

I see three reference planes there. Why cant any of those three faces reference for squareness and perpendicularity to the two crank bores?

Bring it by my shop in woodbridge on a Sunday if you want me to take a look.

 

[HERBXX]

Look up Fast Company Kitchener or Breslau , Scott Miller. I would be surprised if there is anything he can't do, if he has time.

 

[J_F]

if the cases bolt up true
and there's no damage to the OD where bearings are installed
I'm wondering what the need for line boring is?

won't getting the babbit sized correctly and concentric be adequate?

 

[bitzz]

if the cases bolt up true
and there's no damage to the OD where bearings are installed
I'm wondering what the need for line boring is?

won't getting the babbit sized correctly and concentric be adequate?

Here is someone that is catching on...
The point of that babbitt bearing is to remove the need for precise machining (I think it is a pretty dumb setup)(...and I am willing to bet the bearing at the other end of the crank is a "C2" bearing which makes it even weirder).
The soft babbitt allows the shaft to size the bearing and to find it's own center.
In this case "close" is good.
Never forget: British bikes were designed in a pub, and built in a shed.

 

[crankcall]

Here is someone that is catching on...
In this case "close" is good.
Never forget: British bikes were designed in a pub, and built in a shed.

I'm reading a book called the Motorcycle Apprentice , biography of a guy that became an engineer at AMC, (associated motorcycle) ,AJS, Matchless. Some machines had been in place since the late thirties, early forties. The mechanics had designed tooling and process that was essentially a work around for how bad the production machine line was. There was just no money to invest back into the manufacture, which is why you might see babbit bearings in engines , long after the rest of the world had moved on.

 

[Mike-the-Bike]

Metallurgy advances during World War II saw the Babbitt fall out of favour for regular auto use by the beginning of the 1950’s, however they are still used in heavy gasoline powered equipment. They also also used quite a lot in things like horizontal motors, etc. Just ask a Plant Engineer

They are also fairly common in modern military applications. When I was in the RCAF we used to recast Babbitts. It involves melting the old Babbitt material out of the bearing, cleaning it, then clamping it around original shaft and filling up the gap with new molten Babbitt material. We generally coated the shaft with soot from a candle to prevent the Babbitt material from sticking.

Arguably you could assemble the Babbitt and shaft as is, and hope the Babbitt would size its self, but don’t forget, the metal that comes off has to go somewhere, in this case into your new engine.

It was standard practice that we always gave them a light line hone to get an acceptable clearance. I would assume your shaft is round-about an inch in diameter. Depending on the type of Babbitt material, I would generally be looking at clearances around 0.002 per inch of shaft diameter with an additional +0.001 for shafts running at higher RPM’s, with a service limit of around 0.004 -0.005. but check your manual

To be honest, its old technology and there are probably better ways to do it today, but it’s still functional and works well in the right application. I would imagine the originals lasted 40-50 years

Someone mentioned Brad at Steffan. If you live east or even fancy a drive to Oshawa, he will certainly steer you in the right direction.

 

[nornet]

After considerable evaluation of suggestions and proposals I had the work performed by Rob Star (GTAM member) who did an excellent job.
He removed the bulk of material on a lathe and pressed the bushings into the crankcase. For whatever reason the hole became oval. There were several thou left for cleanup and he left took this down to slightly undersize to allow for final finishing.

I am fairly certain that this work was originally done be either line reaming, line burnishing or line honing. It is possible that it was originally line honed but unlikely. The original bushings were only several thou undersize to begin with not the .100 undersize they are manufacturing today.

Mike-the-Bike had some guidelines for babbitt bearing clearances. Fortunately I have a workshop manual for the bike (priced at $1.50) . The suggested bearing clearance is .0015-.002`, very close to what you suggested.

Many thanks to all who contributed.