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Lucas Magneto end housing.
#798186 02/12/20 5:46 pm
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I’m attempting to conjure up a magneto for an upcoming project and needed an end housing for slack wire manual advance, clockwise rotation. I found a new CNC machined one on eBay. Long story short, It looked fine, but was nowhere near a snug fit in the mag housing. It didn’t seem like a good idea to just count on the 3 screws to keep it located in place. That thought was reinforced by a magneto mentor. First order was to make up a mandrel to hold the end housing. Setup in a 4 jaw and the mandrel was turned just so the points cam bore would just slip on. The mandrel won’t indicate any runout and the end housing fit is snug fit. There isn’t enough clearance to register on the reasonably accurate Fowler digital gauge when reefing on it.
I check runout on the shoulder that locates the end housing and it is not Concentric with the cam bore. Upon further checking, it turns out neither is the end housing bearing bore and they are both out by a bunch. So much for CNC.
What is interesting is that I checked 3 other original Lucas end housings and found 2 of them were just as bad. The 3rd housing was not a good fit on the mandrel as it’s cam ring bore was larger. This made it impossible to get an accurate measurement, but it gave me the feeling that it was worse than the other 2. Makes me wonder how many magnetos are running around out there with funky timing.

Last edited by Cyborg; 02/12/20 6:50 pm.
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Re: Lucas Magneto end housing.
Cyborg #798193 02/12/20 6:55 pm
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Originally Posted by Cyborg
Makes me wonder how many magnetos are running around out there with funky timing.
Very interesting results. I'm afraid the answer to the question implied by your last sentence is, a lot.

However, it's not necessarily as bad as the fit you measured. If the recess for the bearing is machined perfectly Concentric with the recess for the cam it wouldn't matter if the end housing were a sloppy fit in the main housing. Moving the end housing around would move the bearing around and at the same time move the cam around by the same amount.[*]

[*] I used "necessarily" as a weasel word when I wrote the above since I was waiting for a phone call and didn't want to take the time to write a longer explanation. While I'm now waiting for another phone call, here's that explanation: If the cam ring were in the same plane as the bearing in that end housing, what I wrote would be accurate. However, because they're offset from each other, moving the end housing sideways by some amount displaces the cam ring in the direction of that movement by the ratio of the relatively small bearing-to-ring separation divided by the much larger bearing-to-bearing separation.

Last edited by Magnetoman; 02/12/20 7:37 pm. Reason: [*]
Re: Lucas Magneto end housing.
Cyborg #798199 02/12/20 8:36 pm
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You can correct a little bit of eccentricity (and/or cam ring inaccuracy) by stoning a cam ring ramp.

But you do need rigidity. Getting a tight fit between the points housing and the mag case has to be a good thing.


Amateur Loctite enthusiast.
Re: Lucas Magneto end housing.
Cyborg #798205 02/12/20 9:05 pm
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The mag body is from a K2FC that I purchased bare and I’m assuming the original end housing was or was supposed to be a snug slip fit. Of the other Lucas mags I have in the bin with the original end housings, they are (albeit cockeyed) quite a snug fit. I would be nervous about moving the end housing to compensate for misalignment. That would mean that the end housing shoulder wasn’t positively locating the end housing in the mag body and I wouldn’t be able to count on the shoulders of the three screws because there would be gaps between the screw shoulders and holes in the end housing (unless I make up screws with larger shoulders and redrill the holes in the end cover). It would only be the friction between the two ( and or shims) that would keep it from moving Y/N? Wouldn’t the pulsating from the magnets tend to make the end housing want to walk around? BTW, are the K2FC magnets stronger than the run of the mill mags?

I think for me it’s a mute point anyway because the recess for the bearing in not Concentric to the cam ring bore, nor is it Concentric to the shoulder on the end housing. All three are operating in their own little world.
Using the cam bore as datum, the shoulder is off by a little over .0075” and the bearing bore is off by .0085 which means the shoulder and bearing bore are only off by .001” from each other. I’m assuming this is what happens when one assumes CNC machining is so wonderful, you are able to ignore QC checks. Seems to me that being off that much would cause a bit of a gong show depending on where the runout ended up in relation to the bumpy bits on the cam ring.

I’ll machine down the shoulder, add a chunk of something and then machine it down to size. There isn’t room for a top hat, so a simple ring with a slight interference fit and a bit of Loctite 648. I may be able to do the same with the bearing bore, but there isn’t a lot of meat between it and the manual advance bore. The end housing is set up for a 37mm bearing, so I do have the option of sleeving it down and using the smaller bearing.

[Linked Image from live.staticflickr.com]0D053A82-9320-4FB0-8100-E96473AA3764 by First Last, on Flickr



Last edited by Cyborg; 02/12/20 11:08 pm. Reason: Sounded a bit off the way I initially wrote it.
Re: Lucas Magneto end housing.
triton thrasher #798206 02/12/20 9:14 pm
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Originally Posted by triton thrasher
You can correct a little bit of eccentricity (and/or cam ring inaccuracy) by stoning a cam ring ramp..


Never thought about using the cam to adjust things. I think (as per the measurements above) in this case stoning isn’t an option. Plus with luck I can get the shoulder a snug fit and the cam bore/ bearing bore running in harmony.




Last edited by Cyborg; 02/12/20 9:16 pm.
Re: Lucas Magneto end housing.
Cyborg #798244 02/13/20 5:07 pm
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Originally Posted by Cyborg
I’m assuming the original end housing was or was supposed to be a snug slip fit....
(unless I make up screws with larger shoulders and redrill the holes in the end cover).
Wouldn’t the pulsating from the magnets tend to make the end housing want to walk around?
BTW, are the K2FC magnets stronger than the run of the mill mags?
I’ll machine down the shoulder, add a chunk of something and then machine it down to size.... There isn’t room for a top hat, so a simple ring with a slight interference fit and a bit of Loctite 648. ...
I do have the option of sleeving it down and using the smaller bearing.
Taking the above extracts one at a time,

I don't remember any of the Lucas-made end housings I've worked with being a loose fit as you've found with your aftermarket one

In principle, the force applied to the armature by the magnet is equal from side-to-side so there would be no net force on the bearing to make it walk. Also, in principle, the armature is perfectly balanced so it wouldn't cause a net force, either. However, in practice...

As far as I can tell without x-raying or dissecting the bodies, the K2FC has the same slug of Alnico cast into it as does a K2F.

[Linked Image]

As can be seen, even if someone wanted to, there isn't much room in the housing to make the slug of Alnico any larger. The differences are in having things held in place by screws instead of clips.

I just now looked at eBay to see if I could find a listing for the CNC end cap you bought but didn't find it. However, I did find several stock Lucas ones. I'm certainly guilty of spending excessive amounts of time reviving worn out parts in order to keep everything as original as possible, but you're spending that time on an aftermarket part. Why aren't you buying a replacement Lucas instead of doing all that work on an aftermarket part when "genuine" ones are readily available?

Re: Lucas Magneto end housing.
Cyborg #798248 02/13/20 5:54 pm
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The K2F on my Atlas was sufficiently off that there was an 11 degree difference in timing between the cylinders. I took it over to Doug Wood who machined the back of the cam a touch and shimmed one side to get it Concentric with armature. Ended up with a half a degree difference. What a difference in the way it ran!

Ed from NJ

Re: Lucas Magneto end housing.
Cyborg #798269 02/14/20 12:01 am
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Trying to apply logic to most things I do probably isn’t time well spent. Although I have several magnetos in my collection, they are one of the very few items that I send out to be rebuilt. That has allowed me to keep my head firmly stuck in the sand with regards to that subject. I know that is flawed thinking and unwise. My somewhat feeble excuse is my preoccupation with learning how to TIG weld aluminum and absorb the contents of the Machinery’s Handbook.
I wasn’t aware that a replacement Lucas part was still readily available. I understand that they come up on eBay from time to time, but I wasn’t able to find one. I’m not sure the one I need came on very many motorcycles. It was used on the KVF TT and a K2FC that was on some sort of Royal Enfield as far as I know. The slack wire manual advance, clockwise rotation and need to fit on the K2FC appears to have limited my choices. The fellow said he has sold lots without any problems, but unlikely anyone went to the trouble to make a mandrel and check for runout. I pride myself on being strange and unusual. Other than my need to become a hermit, It has served me well.
Anyway, now that I know what I’m dealing with, it should be a relatively straightforward fix... at least that’s what I’m telling myself. The seller did do a partial refund, although that was because it was advertised to fit a KVF, which it does not. At that point the plan switched to the K2FC... then I discovered the questionable clearance and the fact that nothing was Concentric. In fairness I can’t lay all of the blame on the end housing. Although I believe the shoulder should be larger in diameter, the recess in the K2FC mag housing appears slightly larger when compared to KVF, K2F housings.

As for the end housing bearing... is there any real reason why I shouldn’t just sleeve it down and use a 35mm bearing instead of the 37mm? That way I don’t have to open up the bearing bore which is getting close to the manual advance bore. Not likely the bike will ever get ridden in anger for hours on end.

Thank you for the reply/images BTW. Much appreciated.

Last edited by Cyborg; 02/14/20 12:15 am.
Re: Lucas Magneto end housing.
edunham #798270 02/14/20 12:07 am
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Originally Posted by edunham
The K2F on my Atlas was sufficiently off that there was an 11 degree difference in timing between the cylinders. I took it over to Doug Wood who machined the back of the cam a touch and shimmed one side to get it Concentric with armature. Ended up with a half a degree difference. What a difference in the way it ran!

Ed from NJ



If the points gap is supposed to be .012 to .014, I wonder what .0085 runout would do?

Re: Lucas Magneto end housing.
Cyborg #798271 02/14/20 12:52 am
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Originally Posted by Cyborg
Trying to apply logic to most things I do probably isn’t time well spent.
Sorry if you inferred from what I wrote that I thought anything either of us does with motorcycles is logical.

Originally Posted by Cyborg
the recess in the K2FC mag housing appears slightly larger when compared to KVF, K2F housings.
I have quite a few K2F housings, at least two K2FC housings, and a complete KVF to compare, but it likely won't be until the weekend -- if then -- that I'll have a chance to look into their dark recesses.

Originally Posted by Cyborg
is there any real reason why I shouldn’t just sleeve it down and use a 35mm bearing instead of the 37mm?
Given the light use you intend, I can't think of any reason at all. I assume they went to a larger bearing because under heavy use the smaller bearing sometimes gave problems.

I do have to point out that the cause of the timing problems some of you are having with twin magnetos is quite simple. You have one too many cylinders on your motorcycles. I have no such problems on any of my single-cylinder motorcycles so, clearly, it is that second cylinder that is responsible for messing up the timing.

Re: Lucas Magneto end housing.
Cyborg #798275 02/14/20 4:07 am
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Is that what is preventing you from dragging that lesser motorcycle out from under your bench? The timing be out of whack and you have to come to terms with one cylinder getting a lesser spark! Not only does it have two cylinders, the ET 109/13 , ET109/9, and ET109/8 engine studs have screwdriver slots cut in them!

At the risk of sounding like I want to be spoon fed.... do you happen to know what thread is used on the screw on points cover for the K2FC? I want one like the KVF TT version so assuming I‘l have to whittle one out of 6061. Based on the CNC housing it’s 2 1/8 20 TPI 60 degree, but should probably verify.

I was told that one of the other differences with the K2FC was the drive end bearing is supported by a steel ring that is cast into the housing and they sometimes work their was loose. Thankfully mine is still where it is supposed to be.

The recess that I was referring to is where the shoulder on the end housing is supposed to locate itself. I think mine is slightly larger than it is supposed to be. I haven’t bothered to measure it yet, but when I remove an end housing off a K2F ( and it took a bit of effort to get it off) and try it on the K2FC it still has a slight amount of play. Trying to be somewhat charitable when referring to my CNC end cover. One good thing is the cam ring is really snug and will actually need to be lapped in a bit, so it can rotate for the manual advance. That is rotate assuming I can figure out where to grind the slots in the cam ring.

I was looking at the red pickups that are used on the K2FC etc, I discovered they are painted with red insulating varnish. Where have I been? Never (or don’t recall) heard of the stuff.

Last edited by Cyborg; 02/14/20 1:49 pm.
Re: Lucas Magneto end housing.
Cyborg #798304 02/14/20 6:11 pm
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Originally Posted by Cyborg
do you happen to know what thread is used on the screw on points cover for the K2FC?
Assuming the angles on my thread pitch gauge are accurate, the thread is 60-deg. 20 tpi.

[Linked Image]

It's hard to tell from the photograph but the threads are rounded at the tops and bottoms as called for in the specification of CEI.

Originally Posted by Cyborg
I was told that one of the other differences with the K2FC was the drive end bearing is supported by a steel ring that is cast into the housing
Based on only one measurement of each type of body the K2FC is 14 grams heavier. However, it seems more likely that ½-oz. difference is due to factors other than a steel ring hiding inside the K2FC body.

Originally Posted by Cyborg
The recess that I was referring to is where the shoulder on the end housing is supposed to locate itself.
For what it's worth, the K2FC end cap in the above photograph was a tight-ish fit in the three or four K2F bodies I tried it with, with no perceptible play once in place. Interestingly, measured with calipers (i.e. not good to better than a few thou.) the OD of the shoulder is 2.178", which isn't any reasonable fraction.

Originally Posted by Cyborg
assuming I can figure out where to grind the slots in the cam ring.
I have a KVF cam ring that I thought was on a particular shelf, but clearly at some point I moved it to a better location so I could find it easier.[*] Sigh...


[*]Found it! It actually was on the shelf where I thought it should be, but hiding behind a baggie holding the mag portion of a magdyno whose base I modified and I rebuilt to carry as a backup on the Cannonball.

[Linked Image]

What measurements would it be useful for you to have? The two easiest to measure fixed points are the hole and the slot, along with the angle between them. What you probably also would need is the angular location of the slot with respect to the point where the cam starts to rise. But, is it because it is for a lesser machine that the cam you have for it doesn't have a slot in it already?

Last edited by Magnetoman; 02/14/20 8:41 pm. Reason: [*]
Re: Lucas Magneto end housing.
Cyborg #798389 02/15/20 5:17 pm
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I have what is supposed to be a 459155 ring, but need to modify it for slack wire advance. It’s the location of the wide slot ( to allow, but limit rotation) and the slot for the manual advance cable that I need to figure out. In other words, if I was going to copy one, it would need to be from a KVF TT.

Bill from Brightspark was kind enough to send me some info on how to locate them from scratch. Glad he did, because there are a couple of pitfalls that I was unaware of. That's my problem with magnetos in particular... I don’t know what I don’t know.

I haven’t really thought this through. Perhaps due to the fact that I’m using an end housing with some issues and basically cobbling this thing together out of odds and ends, maybe it’s better to work out the location of the slots rather than copy one? Or at least work things out and then compare the results to a known good one?

I’m not sure if the manual advance housings normally come with an eccentric screw for fine tuning, but this end housing doesn’t have the boss for that screw. Just two untapped holes for limiting screws in behind the ring.


[Linked Image from live.staticflickr.com]6F4A2A73-27EE-4E4D-AC4D-903AAA685F5B by First Last, on Flickr

[Linked Image from live.staticflickr.com]CE643FD8-13BE-4ECD-9E2C-0F710C50F971 by First Last, on Flickr

Re: Lucas Magneto end housing.
Cyborg #798390 02/15/20 5:26 pm
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By the way, thank you for your assistance. Playing with the magneto is helping to distract me from this excruciatingly painful exercise.




[Linked Image from live.staticflickr.com]3799ACA8-71E2-4CDA-96E2-10D20A197478 by First Last, on Flickr

Re: Lucas Magneto end housing.
Cyborg #799228 02/24/20 4:14 pm
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Waiting for snaps to arrive, so spent some time on the end housing.

[Linked Image from live.staticflickr.com]873936B6-E6F3-4541-BF2D-D6D923CBDB4D by First Last, on Flickr

[Linked Image from live.staticflickr.com]2A35DED7-6606-4637-A5DC-E6A2C865D64F by First Last, on Flickr

[Linked Image from live.staticflickr.com]EC39426B-095A-4A40-8DCB-EC76B08D5DFA by First Last, on Flickr

Somewhere between a slip and interference fit, waiting for the Loctite 648 to set up.

[Linked Image from live.staticflickr.com]3F5F4E3F-4864-44D6-B665-5586906F8B0F by First Last, on Flickr

Arts and crafts. The holders are worn rocker spindles (from a lesser brand), because I can’t throw out any round stock.

[Linked Image from live.staticflickr.com]A9D6F639-5ED5-433C-B925-258361F36E24 by First Last, on Flickr

Re: Lucas Magneto end housing.
Cyborg #799272 02/25/20 12:16 am
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Machining down the shoulder on the end housing is straightforward. Just make it a slip fit to the mag housing. The bearing bore size in the end housing is not quite so straightforward. I measured the bearing bores on 4 end housings and they range from 35.56mm to 35.74 mm. An available bore gauge in that range is limited to a cheap knockoff of the Starratt, but measured a few times to get a consensus. The paper insulators come in a choice of .25mm (.010”) or .33mm (.013”).

Anyone out there know how much the paper insulators will compress or should compress? These ones have a plastic coating on the outside to ease installation. I can warm the housing up and get it to expand a bit.

The bearing OD is 35.01 mm according to the mic, (but that’s relying on the “odometer”), so if I use a .25mm insulator, that would require a 35.51 bore for things to just slip together. Any comments on what sort of interference fit there should be? As in maybe bore it to 35.41 and hope the insulator doesn’t object.

[Linked Image from live.staticflickr.com]7DB64706-A676-4568-AE8B-14980D258ED2 by First Last, on Flickr

Last edited by Cyborg; 02/25/20 5:32 pm.
Re: Lucas Magneto end housing.
Cyborg #799725 03/01/20 3:23 pm
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No takers on that question, so will try a few insulators and figure it out. Hopefully it won’t turn into a need to get into paper insulator manufacturing.

Another question.... I’m working with a machine drawing from 1957. At the top of the drawing in large letters it says.. “ ENGLISH PROJECTION “. Anyone out there know what that term means in the British engineering/machining world?

Re: Lucas Magneto end housing.
Cyborg #799780 03/02/20 2:43 am
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"English Projection" refers to how the elevation or side view is projected relative to the top view on a 2-dimensional drawing. The British and US drafting standards differ. Same information either way, it is just whether you view it from top to bottom or from bottom to top. Not easy for me to explain, but as long as you can visualize the part don't worry about it.

Re: Lucas Magneto end housing.
Cyborg #799782 03/02/20 3:06 am
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Thanks for the explanation. I also asked on a machining forum and got the understanding that it had to do with the view, but it still couldn’t quite grasp it. Your explanation did a better job of clearing it up. I am able visualize the part and figure out the info I need, so good to go. I did find it odd that a web search didn’t turn up anything, as in no mention of the term.. period. Anyway, I’ll take your advice and just go make some shavings.

Re: Lucas Magneto end housing.
Cyborg #800349 03/08/20 12:06 am
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Tip for machining small fasteners. Clean out the shavings tray before starting. 10 minutes making a screw and then 15 more looking for it after it gets parted off. 3BA screws can hide fairly well. Still have to mill the slots in them and drill holes for safety wire.

[Linked Image from live.staticflickr.com]59F2E82F-ACB6-4FC4-BB16-0D9E17360585 by First Last, on Flickr

Re: Lucas Magneto end housing.
Cyborg #800394 03/08/20 10:57 am
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Been a very long time since I dropped blobs of ink from my Roterings onto nice white cartlidge paper.
Have been a slob all my life & too old to change now.
The words they should have been using was 1st angle protection or 3rd angle projection .
For some reason it was a big thing when I was studying but it never really made sense because the item is the same no matter which way you view it .
But examiners seem to enjoy writing obtuse questions about it .
However this is a nice simple explanation with pictures .
Calling either one of the US or English is a bit of a stretch as I have seen both used within a single job.
It is probably just what the draughts person is most comfortable using .
The only important thing is the little cone marker should be within the title box just so readers know

This time with the link
Difference between 1st & 3rd angle projections.
as for bad machining , it was the 50's
Most production machines worked between stops so only the very first one after the machine setter had done the adjustments would be accurate.
Remember we are talking about high carbon steel tooling, not nice carbide tips that retain their size for a very long time.
As for CNC
the story is same with computers, garbage in = garbage out.
Even worse is the stuff done on reproduction machins that scan the original the cut an exact copy
If the original was bad, they make a bad copy and from what I ( and most others have already noted ) , they were not all that good when new .
It was one of Gerry Bristows bit bug bears that CNC machined from a billet is nothing more than description of the method of machining and not a guarantee of quality in any way shape or form.

Last edited by BSA_WM20; 03/08/20 11:07 am. Reason: forgot the link

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Re: Lucas Magneto end housing.
Cyborg #800441 03/08/20 10:51 pm
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Thanks for the link Trevor. I more or less expected some variation in the OEM Lucas bits, but really didn’t expect quite that much. Especially with something like a bearing bore, even if it has an insulator in there. Could be that 30 years working for the Japanese altered my perspective.
I turned down the end housing shoulder so it takes a slight twist to get it home all the way in the mag housing. I’ll do the bearing bore tomorrow. It’s taking a while because I’m supposed to be finishing another project before I get totally sidetracked with this. Drilled the safety wire holes and slots in the screws. Bit of a nuisance making screws, but the only end housing ones I could find were from Germany and the amount the guy wanted for postage was totally bizarre. Probably not as much of a nuisance as making the screw on points cover though.

Do you still have a WM20 ? Military version?

[Linked Image from live.staticflickr.com]431BC2CA-D478-4FB4-BE41-FFC32583FBAC by First Last, on Flickr

Re: Lucas Magneto end housing.
Cyborg #800479 03/09/20 1:42 pm
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It is easy to forget just how old world the designs of out beloved BSA's are.
This is particularly the case if you also have modern bikes .
Out mounts are failry well over designed, under stressed and will run OK with so much mal alignments it is not funny.
They were built for daily transport just about everywhere on the planet with the exception of the USA where they were by & large week end toys .
You can mix & match all sorts of parts that really do not go together & they wiill run.
Only when you start looking for the other 9/10's of performance do you start finding the short comings .
We forget they were designed in the days of slide rules so any modification had to be made in metal and tested, not sun on a computer simulation .
Making experimental parts is not cheap and Post WWII margins dropped like a stone so the money was not there to try this or that.
They used what they knew would work .

Things like A65's throwing rods were virtually unheard of in my "wild days " down here in Oz yet they seem to be common place in the USA.


Bike Beesa
Trevor
Re: Lucas Magneto end housing.
Cyborg #801988 03/20/20 12:24 am
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Phase 3 of points cover 2.0
Complete with 2 1/8 20 “RH” TPI

#toomuchtimeonmyhands

[Linked Image from live.staticflickr.com]179375B5-C029-4FC1-BBE7-B4F449F1341E by First Last, on Flickr

Last edited by Cyborg; 03/20/20 12:25 am.
Re: Lucas Magneto end housing.
Cyborg #802815 03/26/20 12:45 am
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So now that I have a lump of aluminum that screws onto the end housing to cover the points, I need to make the breather cover. Never made one before, but thought a simple stamping die would be the way to go. Turned the male portion on the lathe with the idea of using it to form the female die. The female die just consisted of a suitable piece of 6061 with a hole bored in it. Both pieces were put in the oven along with a container of Cerrobend. Once up to temperature, the molten Cerrobend was poured into the female die...male die inserted into the molten metal and held down with a weight while everything was allowed to cool. There was enough Cerrobend that the excess was forced out by the weight. Once cooled, the male die was removed to reveal several voids. Another attempt produced better results, but still contained some voids.
The mystery is... there are no areas that would be prone to trapping air and given the density of the Cerrobend any air should be forced out in short order.
Although I filled the voids with epoxy and clean things up on the lathe, I also made another female die, but on the lathe this time. So much for shortcuts.

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