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Originally Posted by Magnetoman
[Linked Image]
Are you using a paper towel to diffuse your photo lighting?
It makes the neatest groovy pattern on that chrome cover.

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Originally Posted by Stuart Kirk
A seal holder could be made with a flange to fit behind that clip.
Yes, if I were sufficiently motivated, and it's not clear that I am, I could fabricate my own Gold Star-like seal holder to replace the spacer that's under the circlip. I'd have to polish the mating portion of the sprocket as well.

[Linked Image]

Originally Posted by Stuart Kirk
Are you using a paper towel to diffuse your photo lighting?
It was the same type of towel that I often sit objects on that I photograph. Without something above the chrome to block the direct light from the ceiling fixtures the reflection was too bright. Shiny objects are difficult to photograph and it would have taken quite a bit of time to set up a proper diffusion tent, but the pattern from the towel did look nice.

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Originally Posted by Magnetoman
Originally Posted by Stuart Kirk
A seal holder could be made with a flange to fit behind that clip.
Yes, if I were sufficiently motivated, and it's not clear that I am, I could fabricate my own Gold Star-like seal holder to replace the spacer that's under the circlip. I'd have to polish the mating portion of the sprocket as well.
That's a point. Could a BSA pre-unit gearbox mainshaft seal be modified to suit?

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Hi MM and All
From previously seeing other Burman gearbox cases where welding was attempted I would be reluctant to try and
reclaim the edge of the kickstart housing by TIG welding
(Unless you can get the case boiled up in a pot of trichloroethylene beforehand ????? )

As the damage is at the bottom of the case I would opt to use some chemical metal to build up the lip

Remember "The Better is the worst enemy of the Good"
John

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The first engine I stripped down was a 1960 BSA A7 Shooting Star.
I had bought it then tried it out on the local bypass to "see what it will do".
On that day no more than 75mph as the driveside conrod broke through the crankcase.
My motorcycle mentor was the superintendent of a large engineering company employing 12000 people.
We cleaned up the hole in the crankcase and filed a repair piece to fit the hole.
Then the crankcase half and the repair piece went into the engineering works and spent three days in a large 20' X 10' trike bath.
The parts were then welded together by a Lloyds welder using the then new argon arc process.
No leaks and I did several tens of thousands of miles afterwards on that bike with no problems.
The problem is that the oil gets into the pores of the casting and it is the devils own job to get rid of it.
And if you dont get rid of all the oil then forget about a good leak tight weld.
Just my two cents worth of course.

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Originally Posted by Shane in Oz
Could a BSA pre-unit gearbox mainshaft seal be modified to suit?
I haven't measured the diameter of the sprocket, and I don't remember the OD and ID of a BSA seal, but even if they're different a seal holder could be made from scratch. However, that would require someone who was sufficiently motivated to do so...

Originally Posted by chaterlea25
(Unless you can get the case boiled up in a pot of trichloroethylene beforehand ????? )
That can be easily arranged.

Originally Posted by Tridentman
And if you dont get rid of all the oil then forget about a good leak tight weld.
In this case, the weld will be 99% cosmetic. As long as the sealed bearing keeps oil/grease out of that particular compartment all the weld will be keeping in is air. If the sealed bearing doesn't keep oil/grease out, it still doesn't have to be leak tight because the hole around the kick starter crank is an even better path for it to escape.

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Its not clear to me whether the gearbox output bearing is actually sealed or not. I can see that there is a circlip holding a shield but does it actually provide any sealing?

What I've done on various other BSA's and Nortons is to use a sealed gearbox output bearing (2RS suffix) in conjunction with the existing unreliable outer seal, so a kind of belt and braces approach.

If there are additional leaks past the main shaft and bearing then I wouldn't hesitate to use some kind of sealant in modest quantities.

I appreciate that there may not be a sealed bearing with the appropriate dimensions and I'm probably preaching to the converted, but I thought I would mention it anyway.


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Originally Posted by gunner
Its not clear to me whether the gearbox output bearing is actually sealed or not.
As can be seen from the following photograph I took three years ago, it is sealed.

[Linked Image]

However, only a portion of the inner race on the other side of the bearing can be seen in the following photograph so it's not possible to tell if there are seals on both sides.

[Linked Image]

What is difficult to see in the photograph is that the inner race is recessed by 0.101" from the inner surface of the case. The surface of the sleeve gear that is pulled tight against the inner race is on a "collar" next to the gear itself that is 0.213" high, resulting in a gap of 0.112" between the inner face of the sleeve gear and wall of the case. I could make a 0.110"-thick teflon washer with an OD the same as the root of the gear teeth to better keep any wayward oil/grease away from the bearing, but I'm not sure whether it's worth the effort. Although, having said that, the effort would be relatively little.

An additional pair of measurements is the OD of the "collar" is 1.615" and the ID of the hole in the case is 1.661", so there is a 0.023" gap between the two.

[Linked Image]

Given the shallowness of the hole and the cramped area inside the case, this is a measurement that would have been difficult to make without a 3-point micrometer having its measuring probes only 0.025" above the bottom of the instrument.

[Linked Image]

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Originally Posted by Magnetoman
Given the shallowness of the hole and the cramped area inside the case, this is a measurement that would have been difficult to make without a 3-point micrometer having its measuring probes only 0.025" above the bottom of the instrument.
[Linked Image]
Methinks MM has secretly bought up all the three point mikes he could and is now working to create a market for them.
So at least wipe the thing off before getting that closeup! 2c
BTW, how do you get an accurate measurement when it's got all those crumbs on it?

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Originally Posted by Magnetoman
Originally Posted by Stuart Kirk
Are you using a paper towel to diffuse your photo lighting?
It was the same type of towel that I often sit objects on. .........the pattern from the towel did look nice.
Yeah, that's what I thought. Interesting memories. It kinda reminds me of the light shows at rock concerts during the sixties and early seventies.

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Originally Posted by Stuart Kirk
It kinda reminds me of the light shows at rock concerts during the sixties and early seventies.
I thought that anyone who could remember those rock concerts wasn't there...

Originally Posted by Stuart Kirk
Methinks MM has secretly bought up all the three point mikes he could and is now working to create a market for them.
Those photographs simultaneously accomplish three useful things: 1) cause angst in Cyborg, 2) justify having squandered the money to buy them, 3) show people their usefulness for an otherwise-difficult measurement.

While waiting for the layshaft O-rings to be delivered, I turned to repairing the outer case. I don't know the reason, but I just haven't found the problems welding old motorcycle castings that people often describe (knock wood). The Burman case looked perfectly weldable so I spent maybe two minutes cleaning the area with a wire brush and acetone until the paper towel was no longer stained. Although clean, it still looked like the photos in a previous post.

The welding proceeded without problem, and after less than 15 minutes, including getting ready to weld and shutting down afterwards, the inside and outside of the case looked like the first photograph.

[Linked Image]

A job like this isn't a time to go for the stack-of-dimes look since most of the Al will be removed afterwards. The essential thing is to not find later that you applied a bit less Al than needed in some location. More is better.

Having added the Al, the next step was to file away the excess on the outside while trying to reproduce the original contour.

[Linked Image]

The filing might have taken ten minutes, starting with a somewhat coarse file for rapid material removal and moving to finer files as it neared completion.

Next, I moved to the mill. After loading the rotary table onto the mill and centering it to ±0.0005" I paused to cut a taper in a piece of scrap ¾" Al in the lathe, that I then used in the mill to center the case on the rotary table.

[Linked Image]

When trying to precisely center something this way it helps a lot to start with it close, and then home in on the final centering. That was my original plan, but when the taper moved the case into position I realized I didn't have to work to the nearest nanometer in order to do a fine job machining the case. All I did was lightly snug the clamps on the case, insert the taper to center the case, tighten the clamps, and declare it good enough.

As seen in the next photograph I only had to remove Al from a relatively short arc so even if the case had been off by 0.010" from being perfectly centered (and I don't think it could have been off by more than ~0.002"), it wouldn't have mattered.

[Linked Image]

The final photograph shows the case fresh out of the mill with only the chips removed.

[Linked Image]

Even though the case doesn't have to hold anything, I'd guarantee that weld on a 93-year old cast Al gearbox to be leak tight even if it were on an oil tank. Total time: less than two hours.

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As much as it pains me to say this... good job fixing the case. I’m unsure if I should feel honoured that I received top billing, but thanks I guess.
Your day was definitely more fruitful than mine, but I did manage to use some of that Cerrobend. I needed a 14 flute 64mm filter socket to quell a small insurrection and couldn’t find one locally. I like that stuff, but too bad it’ll eventually make you a little slack jawed.

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Originally Posted by Cyborg
I did manage to use some of that Cerrobend
Every time I step around that bucket of Cerrobend you forced me to buy I think of how useful it is going to be, but I haven't yet had a task where I can employ it. I can see how forming an oil filter wrench would be just such a task.

Going off topic, after high school I had a summer job in a gas station. My senior co-worker must have been all of a year or two older than me, but owned his own Texaco uniform and was a professional gas station worker whereas I was just a kid. A valuable lesson I learned from him was as a result of changing an oil filter. We couldn't get it to budge, and he eventually said we would have to drive a screwdriver through it in order to turn it. I immediately objected, saying "what if we still can't get it off?" He calmly replied, "if we drive a screwdriver through it, we must get it off." And, we did. But, had we had a bucket of Cerrobend, we would have had an option that was better than an ill-fitting oil filter socket, or the anxiety of driving a screwdriver through it. Still, the valuable lesson of "we must" rather than "what if we can't?" stuck with me and was put to good use a number of times in my life.

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You may not realize it yet, but along with the bucket of Cerrobend, you need some Cerrosafe. Might come in handy if you can’t reach into a bore with your highfalutin 3 point bore gauges.

I need to stay away from this thread... all of a sudden I’m getting uncontrollable urges to sift through the pile and assemble a dolls head gearbox.

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Looking at that case it looks to be a pretty ideal component from a sand casting viewpoint.
The kickstart boss would be the feed and gravity would mean a really nice casting with little porosity.
Especially the area needing to be built up as it is near to the pour feed.
Just my two cents worth of course.

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Originally Posted by Hugh Jörgen
My mentor would have calmly replied with an open hand backside my head and a gruff "Just get the screwdriver punk."
That's the same mentoring technique I used with my graduate students...

Originally Posted by Cyborg
you need some Cerrosafe
It's an interesting exercise in product naming that they call it Cerrosafe with it having "only" 8.5% cadmium, whereas Cerrobend has 10%. In any case, Cyborg's recommendation is because people use Cerrosafe to make castings from which they then make measurements. The reason this particular alloy is useful for this purpose is because it shrinks for the first 30 min. after solidifying, making it easy to remove from the mold, then expands. The claim is that one hour after it solidifies it will have returned to "exactly" the original size of the mold. Before falling for Cyborg's possible ruse to get me to store even more cadmium in the garage, I'd need to research in detail just how exact that "exactly" is, since I'm a lot more comfortable with actual dimensions and error bars than I am with descriptions like "exactly."

Originally Posted by Tridentman
Looking at that case it looks to be a pretty ideal component from a sand casting viewpoint.
I agree. However, in my half-vast experience I've yet to weld a motorcycle casting where the often-mentioned "porosity" has been a problem (again, knock wood). On castings I always begin with a low-amperage arc that I run across the zone to be welded to see if anything bubbles up from below. If it does (which it didn't with the Ariel gearbox), I then stop to clean it with a wire brush before proceeding to weld. No casting I've welded so far (knock wood...) has stored oil anything like the Permian Basin, instead with the contaminants in quite finite quantity, confined to very near the surface, and easily dealt with.

Maybe it's the development of improved, inverter, welding equipment in recent years (possible), my skill (unlikely), or luck (probable), but so far the dreaded "porosity" that people often mention when the subject of welding motorcycle cases comes up just hasn't been an issue (knock wood...).

On this subject, and in case anyone is interested, I used the following settings on my Miller Dynasty 200DX when welding that gearbox casting:

Polarity: AC
Balance: 70%.
Waveshape: advanced square wave.
AC Frequency: 100 Hz
Amps: Set at 170 A but I used the foot pedal to control it at less than that
Electrode: 1/16" lanthanated tungsten
Cup: #7 with gas diffuser 'lens'
Gas: 15 cfh Ar
Filler: 4043 (this is always my first choice for castings)

Except for the Amps on thinner or thicker castings (and a 50/50 He/Ar mixture for a really thick casting), and Balance on dirtier ones (e.g. 60% would give more cleaning action), my settings for any motorcycle casting I've welded so far would have been pretty close to these. That doesn't mean they are the best possible settings, only that they've worked well enough for me.

The O-rings were delivered late yesterday afternoon so, with the cosmetic surgery on the outer case complete, today it was time to cut the necessary groove in the hole for the layshaft.

I was surprised to discover that 'Machinery's Handbook' doesn't contain any information on O-ring grooves. Conveniently, though Parker has an on-line calculator that told me I need a groove with OD 0.725".

[Linked Image]

Since they assume the the hole for the layshaft has an OD of 0.6270", but mine is 0.6320" this means the groove it needs has to be cut to a depth (0.725"–0.632")/2 – 0.005" = 0.0415" below its surface. Also, my O-ring grooving tool has a width of 0.064" and the Parker calculator calls for 0.093" so once I reach the correct depth I'll have to translate the case by 0.029" to give the groove the required width.

As the next photograph shows, the OD of the O-ring is small enough that the groove for it won't break through into the hole for the layshaft locating peg.

[Linked Image]

After centering the rotary table in the mill to 0.0005" I then used the same tapered peg I had used yesterday to register the other hole in the case, to register the hole for the layshaft.

[Linked Image]

However, unlike yesterday's milling job, today's called for greater precision. Referring to the Parker data above, they specify dimensions to with a few thou. So, with the case approximately centered, I then lightly snugged the clamps and gently tapped the case until I had it centered to 0.002", as shown in the next photograph.

[Linked Image]

It's not that I gave up when I got it to 0.002", but that the hole was slightly oval and the best compromise I could achieve left a maximum runout of this amount in one dimension.

With the case centered and clamped down I then moved the table in one direction until the O-ring grooving cutter touched the wall, then advanced it a further 0.042" in two stages, each time slowly cranking the rotary table through 360°. When finished with that I lowered the cutter a further 0.029" in the hole and finished the groove.

The final photograph is a grease's eye view of the O-ring installed in the freshly-cut groove.

[Linked Image]

As can be seen, the hole for the locating peg goes through to the outside world so I will be making a short Al plug for it.

When I install the layshaft there will be heavy grease on the O-ring along with Permatex PermaShield on the portion of the shaft inboard of the O-ring, to do my best to make sure the oil/grease mixture stays inside. Or, when it scoffs at my pitiful attempts to constrain it, finds a different escape route...

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Originally Posted by Magnetoman
Originally Posted by Stuart Kirk
It kinda reminds me of the light shows at rock concerts during the sixties and early seventies.
I thought that anyone who could remember those rock concerts wasn't there....
Yes, I've had many opportunities for my life to turn out much worse than It did.

One of the craziest ones was in Palm Springs at least I think it was. I found myself in the middle of a crowd that was trying to break down a fence to get in to the show. The local Motor Cops on Harleys did crowd control by thundering toward us only to lay their bikes down sliding towards the mob like high speed bulldozer blades. And then righting themselves to ride away for another pass.. I've never seen anything like it since.

OK now, back to the Ariel. Very nice, that o-ring job.

Last edited by Stuart Kirk; 05/23/21 4:53 am. Reason: Thought of something else.
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Possibly it may be worth giving that end of the layshaft a little more polished taper to ensure it passes the O ring without damaging it, just a thought.

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Originally Posted by Magnetoman
Originally Posted by Hugh Jörgen
My mentor would have calmly replied with an open hand backside my head and a gruff "Just get the screwdriver punk."
That's the same mentoring technique I used with my graduate students...
Ah. The Socratic Method.


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Originally Posted by Hugh Jörgen
Ah. The Socratic Method.
A few of them might say sometimes it was the Sarcastic Method...

A number of my former students happened to be at the same conference one time, and one of them arranged a group dinner. Describing their perspectives of my "management style" and the various things that went on in my group, many of which I hadn't been aware of, had me laughing so hard my sides hurt and I could barely breathe. One thing stuck in my mind. One of the students said "We always knew what you wanted." I responded "what was that?" He said "Results."

The gearbox is getting dangerously close to being finished, but still remaining before I could reassemble it was to replace the current outboard main shaft bearing with the shielded one, cut oil/grease grooves in two of the three bushes, and hone all three.

So, today I heated the oven with the case in it. The bearing had already fallen halfway out when I removed the case from the oven, so I gently tapped it the rest of the way, cleaned the grease that was trapped behind it with a paper towel and, while the case was still hot, dropped the new bearing in and placed a weight on it to make sure it didn't move when cooling.

[Linked Image]

So, I've traded a name-brand bearing for an unbranded bearing with two shields. I'm counting on this to be an upgrade.

Measurement of the oil groove on the main shaft showed it to be 1/32" wide and ~0.030" deep.

[Linked Image]

I then installed the accessory head on my lathe, not for its bigger swing, but because it decreases the pitch of threads by a factor of 4× to 0.4".

[Linked Image]

Yes, I know you should never leave a key in the chuck, but I wanted to show how I had to move the massive chuck back and forth to center the bush. The 4:1 gearing added to the difficulty. I only have a faceplate and 4-jaw chuck for this accessory head because when I deploy it it's for some special purpose, and a 4-jaw chuck can do everything a 3-jaw can do, albeit a lot more slowly.

I had decided I wanted to cut oil grooves with their helixes to suck oil in from both ends, so this required cutting one of the bushes with a left-handed threading tool. Unfortunately, I discovered I didn't have any left-handed carbide cutting tools of suitable diameter and length to do the job, so I was reduced to grinding my own bit in HSS.

[Linked Image]

I checked and double-checked directions of rotation, and marked them on the two bushes to minimize the chances I would screw up when I cut the grooves.

After cutting grooves in both bushes I pressed them into the gears, so the final step will be honing them to size.

[Linked Image]

Note that the ratio of bearing-to-groove area is ~60/40, which may seem on the small side. However, the ratio of tensile strength of the bronze I used to the SAE660 I could have used is 1.7 so this is equivalent to the load-bearing area of the bronze being nearly 100% of the bush.

Unless I think of something I forgot, the final step before assembling the gearbox will be honing the layshaft and sleeve gear bushes. However, work ended early because of a birthday dinner with one of the granddaughters. First things first; the honing will have to wait until Tuesday.

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Originally Posted by Magnetoman
[Linked Image]

Note that the ratio of bearing-to-groove area is ~60/40, which may seem on the small side. However, the ratio of tensile strength of the bronze I used to the SAE660 I could have used is 1.7 so this is equivalent to the load-bearing area of the bronze being nearly 100% of the bush.
That looks like you run the risk of wearing both the bush and shaft with the rather narrow load-bearing surfaces, especially if it's a hard bronze. A thread form more like an Ajax thread, with the much broader peaks would seem safer, along with a coarser pitch to give twice as much peak width as groove.

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You chumming the waters again with that massive chuck comment?

With oil being sucked in from both ends, is there a passageway in the middle so oil can escape?

Last edited by Cyborg; 05/24/21 2:41 pm.
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Originally Posted by Cyborg
With oil being sucked in from both ends, is there a passageway in the middle so oil can escape?
There's a hole in the center of the gear cluster shaft. Since the spinning of the shaft will leave the pressure at this hole slightly lower than the surrounding area, that will help with the extraction and hence flow rate through the bushes. I cut the helixes to suck oil into the shaft from both ends instead of trying to push it through from one end to the other because there always will be oil at both ends of the shaft to keep the pumps primed, whereas trying to push it through from one end to the other might fail (or might not be as effective) since the hole would allow some or all of the oil to escape rather than making it to the bush at the other end.

Originally Posted by Shane in Oz
That looks like you run the risk of wearing both the bush and shaft with the rather narrow load-bearing surfaces, especially if it's a hard bronze.
The amount of load-bearing area of the present bush is approximately half that of a full bush so I don't think that factor of ~2× will be the difference between it working, and it wearing (knock wood). Also, other than the initial few revolutions, the gear cluster will be supported by a film of grease/oil, not the bronze itself. The pressure of the grease/oil will be born by the bronze but, as I mentioned in my previous post, the tensile strength is significantly greater than the SAE 660 that normally would be used for such bushes.

However, if I had it to do over I would take the time to form a narrower cutting tool. Or, see if I could manually broach a coarser pitch in the mill by simultaneously moving the quill while turning the crank on the dividing head. The latter would have to be done in a single pass since I couldn't hope to accurately reproduce the motions for a second pass.

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You could probably borrow an idea or two from the rifling community. I like this concept.... maybe a rack and pinion off a garden tractor? You wouldn’t need a long rack for just a bushing. Use some bits from your taper attachment? The logic of spending a week to make the thing might escape some folk. There are other versions that just use a twisted flat bar or a piece of small round stock that spirals around a piece of larger round stock and then used to rotate the cutter.



1 member likes this: Magnetoman
Joined: Sep 2004
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Britbike forum member
Joined: Sep 2004
Posts: 1,641
Likes: 138
Looks like you've done a great job on the gearbox and keeping it free from leaks, lets hope it all works out and no drips appear.

The proof is in the pudding or grease in your case, how long before it will all be finished and ready for the first test ride?


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
1 member likes this: Magnetoman
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