Bocsh Magento Questions

[moddamatt]

So recently I found a Bocsh magneto as well as a magneto front plate for a model t on ebay. They were seperate posts but in doing research on the mount I found that the mount was oringally sold with the type NU4 magneto so I decided it was smart to purchase both. Both pieces are in great condition and only really need a good cleaning.

In looking over what I have and at images online I have a couple of questions.

My magneto seems to be missing a timing arm

As seen in this manual

Per the manual there is a supposed rotation of the armature housing for a 25 to 35 timing difference but not only is the arm missing from my uint the housing on it currently doesn't seem to move at all. Does that mean that maybe my unit was taken apart and the wrong parts were used on reconstruction or was there a staticly timed unit that didn't have adjustment and I just found that one.

How do I mount it to the plate? The mounting holes don't seem to line up on the magneto and plate and the drive shaft seems to long in general. I think I understand how to actaully attach it to the gear drive usung a rubber pad and fitting, kind of like a steering rag joint.
Also is there a special fornt plate needed for mounting the gear drive? I haven't been able to find anything in bosch's material about a different front plate and any instructions I find installing just says to mount it, but some forum posts on here and the Hamb say that certain front plate is needed.
And lastly do I need to get a bosch magneto switch or will using a normal key switch work?

[Tim Williams]

To answer your last question, you don't need a bosch switch, a key switch should work just fine. I do see bosch switches come up in the classifieds every now and then.

Tim

[Dan McEachern]

Yes, these use a non-Ford front cylinder cover. Contact Kevin Pharis as he was reproducing this cover several years ago. Many early models of magnetos did not have the advance feature- Bosch DU4 mags were made both with and without the advance. The coupling for the mag side is pretty much a mirror image of the output shaft. A tapered bore with keyway and a flat plate with two holes for attaching the cloth coupler.

[Don]

Tractor magnetos did not have the advance/retard feature.

Don

[moddamatt]

Hmm It was labeled as a possible tractor magneto so thats probably it, I wonder if the housings are swapable or not. Guess I should try to find one.

[speedytinc]

To answer your last question, you don't need a bosch switch, a key switch should work just fine. I do see bosch switches come up in the classifieds every now and then.

Tim

Doesnt the bosch switch ground the mag for "off"?
So a key switch so wired would be off (grounded) in the "on" position.

I believe if you had the correct advanceable/retardable ring, it would interchange.
There would also be a right or left side arm. The difference being where the cut is to give you an advance range against a pin stop.

[TRDxB2]

To answer your last question, you don't need a bosch switch, a key switch should work just fine. I do see bosch switches come up in the classifieds every now and then.

Tim

Doesnt the bosch switch ground the mag for "off"?
So a key switch so wired would be off (grounded) in the "on" position.

I believe if you had the correct advanceable/retardable ring, it would interchange.
There would also be a right or left side arm. The difference being where the cut is to give you an advance range against a pin stop.

Good point about mag "off" to ground. Some of the early switch backing plates had a provision for a ground in the OFF position. I see that some of the repro backing plates have the contact on the underside of the plate and screw on top. I'll check to see if these are previous or current repros, have a stash. It may be just the pin types have that. The Ford documentation for testing the MAG mentions the use of the GND position for testing. So likely an existing switch plat would work but would need to have t he proper backing plate

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[pete eastwood]

Double check and make sure your magneto is the correct rotation.

[moddamatt]

It looks like I have a clockwise rotation mag. And from what I can tell I probably need a counter clock wise one.

[Duey_C]

I can't think of a tractor magneto that DIDN'T have adjustable timing until the late 30's. And they still had impulse couplers for starting. Some engines? Yes on non adjustable timing.
If the interrupter housing comes right off after removing the cover/cap, you're good to go for easier replacement with an adjustable housing.
I have an American Bosch U series mag and the housing is not removable/adjustable.
Yep, you found that one. Like I did with my U. I can use mine due to the impulse coupler. Apples and oranges tho.
If you can find an AC/CCW points plate you might be able to change rotation. The later DU's and ZR's are easy to change.
Now I want to find a book for the NU4! That's an interesting mag! I may give some false advice about rotation change.
Heck, a push button starter switch wired to ground would make a fine shut off switch. Hook the other wire to the stud on the cap/cover.
Push and hold to shut off.
Got a book, possible where you found yours.
Would a model T engine mind the waste/redundant sparks?
EDIT: Use a kill switch that stays off instead. 9-8-23.

[moddamatt]

Yes, these use a non-Ford front cylinder cover. Contact Kevin Pharis as he was reproducing this cover several years ago. Many early models of magnetos did not have the advance feature- Bosch DU4 mags were made both with and without the advance. The coupling for the mag side is pretty much a mirror image of the output shaft. A tapered bore with keyway and a flat plate with two holes for attaching the cloth coupler.

I'm confused about this, as in Bosch's offical documentation on installing this drive, nothing is ever stated about removing the front cover, the only thing stated is grinding of three bolt heads so that drive sits flat. Its weird that bosch wouldn't say anything about the front plate or even have it in the parts list in their install instructions.

[moddamatt]

I have managed to remove the housing from the back so if I get lucky and find an adujstable one maybe I'll be one step closer to using this mag.

[ThreePedalTapDancer]

They originally used a special front plate with the timer omitted. You can use an early gear cover though.

[Michael Peternell]

Any pictures of the gears? Been hoping Dan would repop a bunch more. I'm running one and have a half dozen more I need gears for.

[moddamatt]

[Michael Peternell]

So recently I found a Bocsh magneto as well as a magneto front plate for a model t on ebay. They were seperate posts but in doing research on the mount I found that the mount was oringally sold with the type NU4 magneto so I decided it was smart to purchase both. Both pieces are in great condition and only really need a good cleaning.
WIN_20230904_11_06_06_Pro.jpg

In looking over what I have and at images online I have a couple of questions.

My magneto seems to be missing a timing arm
WIN_20230904_11_03_44_Pro.jpg
As seen in this manual
nu4-brochure-skinny.jpg
Per the manual there is a supposed rotation of the armature housing for a 25 to 35 timing difference but not only is the arm missing from my uint the housing on it currently doesn't seem to move at all. Does that mean that maybe my unit was taken apart and the wrong parts were used on reconstruction or was there a staticly timed unit that didn't have adjustment and I just found that one.

How do I mount it to the plate? The mounting holes don't seem to line up on the magneto and plate and the drive shaft seems to long in general. I think I understand how to actaully attach it to the gear drive usung a rubber pad and fitting, kind of like a steering rag joint.
Also is there a special fornt plate needed for mounting the gear drive? I haven't been able to find anything in bosch's material about a different front plate and any instructions I find installing just says to mount it, but some forum posts on here and the Hamb say that certain front plate is needed.
And lastly do I need to get a bosch magneto switch or will using a normal key switch work?

A Bosch DU4 will do just fine. Cranking by hand you'll want one with the impulse. With starter shouldn't be needed. The impulse speeds up the rotation generating the spark. For what it's worth!

[Michael Peternell]

20230904_182955.jpg

Those look in great condition!

[Duey_C]

Those gears do look nice!
Matt, would you take a photo or two of the points plate (so we can see which plate you have), the interrupter housing as it mates to the end cap and inside the points cover? If you care not to, that's OK too.
The foolishness below is just extra blah, blah, blah.
Did you get the mounting holes sorted out? The NU is the same old mount pattern at 50x50mm so it's strange it doesn't fit.
P.11 of the book n and i. Note u and v for fun! Metric magnetos with SAE mount and connection hdwe. 3/8-16.
On P.13 I found the 215 stop screw on the top of the end cap, the DU's and ZR's are on the bottom.
The end of the armature on the points end will come right off for capacitor replacement IF you like to work on these things.
P.15 shows two different interrupter housings, 9028 C (shown) & 9029 AC. Poo, more parts to find maybe.
Glad you got yours off. Like the U parts book, sure doesn't show the fixed timing housing part number does it?
Your housing has one tiny slot to fit the 215 stop screw correct? When dirty, that screw looks like a pin but it's slotted.
Such a similar mag to the two-spark DU and they do share a couple parts.
Certainly not an expert nor do I play one on tv. Just boyish intense curiosity.

[moddamatt]

Duel the mounting problem isn't so much the holes but where they are on the actual plate. It seems Bosch had two plates available. One for the NU and on for the DU. Being that the NU uses a slipring for firing and not the gear drive of the DU it is longer and thus to long for what I assume is the DU plate. As for the points plate I think I have found a possible replacement from a Lucas magneto that's for counter clock wise rotation. Will have to buy one and test it. As for the stop screw, it was the first thing I noticed and made me believe that the end cap was removable, as why would there be a screw that wasn't removable.

[Duey_C]

Thank you for the pic! The rubbing block always follows the points. CW.
Gotcha, the dual slip ring makes it a longer mag. I missed that. Strange that Bosch didn't simplify and use two sets of holes instead of two different castings.
Mike, our associate T.M. out east uses four different CW DU's with no impulse couplers. He retards the spark and presto! Fun stuff!
I'd swear he told me he hand cranks at least one... I'd be a ninny without an impulse also until I got used to it.
I like your style Matt! Lucas and someone else copied the Bosch design.
The DU here was dirty enough I had to find the screw slot and clean it out to move it to the other hole.
Very interesting thread to me. Thank you! I'll be quiet now.

[Wayne Sheldon]

Heck, a push button starter switch wired to ground would make a fine shut off switch. Hook the other wire to the stud on the cap/cover.
Push and hold to shut off.

You should make certain that your "kill switch" stays grounded when in the "kill"/"off" position. A "normally open" switch like many starter switches switches through when pressed, and then when released goes back to open.
While using one as a kill switch will work okay? If someone walks by and gives the crank a spin just for kicks? The normally open switch is back at open, not grounded and the engine could start! That happened one time at one of our Endurance Runs. Fortunately, the transmission and brake were set and the car didn't take off, just scared a bunch of people $##+less.

I had a Bosch DU4 magneto and drive on my first T speedster. I loved it! No impulse, and no starter! I usually had to spin it to start it!

[babychadwick]

Just think, it could be a DR4 with impulse that can be used as mar OR dist employing a Bosch coil switch with push button start. Talk about options!

Back on topic my grandfather wired his mag so the spark lever when fully retarded grounded the mag. To start just move down one click and crank.

[Duey_C]

Wayne, you raised an excellent point about what I said about a kill switch and you're right.
In my myopic view, I was thinking about a larger engine that's quite difficult to crank instead. That doesn't excuse me tho.
I could edit out what I said but I won't for continuity.
If I would've had a on-off instead of a momentary switch, I would've used it and said it differently I bet.
Sorry for the drift Matt. Very interesting thread!

[moddamatt]

Drift is alright as long as the info is relavent. I most likely will be getting a bosch amg switch anyways to complete the look/setup. I'm really just in the gather stage of this project, need to get a model A out of the way first. But I do have another question, any recomened mag rebuilders or just people able to test my magnets and coil? Want to get them inspected by someone that know what they are doing.