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Seal selection

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IanH15/10/2021 12:28:50
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107 forum posts
61 photos

I have recently finished a conversion of an ML magneto to coil ignition. This involved squeezing a pair of coils into the magneto body along with some electronics. I have tested the magneto on a car (Morgan 3 wheeler) and the results are very encouraging.

This is very much a prototype, and I am beginning to think about longer term testing and a version 2 with some improved weather protection. I have replaced the original magneto bearings with standard sealed bearings, but I would like something outboard of the sealed bearing to keep water (rain - the magneto is very exposed on the front of the car) out of the magneto body. I thought about a lip seal but wondered about how it would manage with no lubrication? In dry weather it would be running dry. An option might be to remove the seal on the bearing on the lip seal side anticipating some grease from the bearing lubricating the seal.

Does anyone have any recommendations for this application? Probably looking at 3000 rpm, shaft diameter 15mm.

Thanks

Ian

noel shelley15/10/2021 13:14:18
870 forum posts
19 photos

I think I would use a double lip (type R23) in Viton - it has a stainless spring, pick out the out board bearing seal and pack the gap with grease, or simply leave the seal in and pack gap with grease. Good Luck Noel.

J Hancock15/10/2021 13:20:35
781 forum posts

Is there any way you could fit a 'thrower' to the shaft , so that water doesn't get to the lip seal ?

Bo'sun15/10/2021 13:35:57
540 forum posts
2 photos

Hi IanH,

If you've got room for a lip seal, why not another sealed bearing. The seals would at least be lubricated. "Belt & braces" maybe, but what's wrong with that?

IanH15/10/2021 14:08:08
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107 forum posts
61 photos

That makes me wonder about using a separate seal at all - maybe just let the sealed bearing do its job?

Ian

J Hancock15/10/2021 16:40:59
781 forum posts

That sealed bearing will not keep water out for very long.

old mart15/10/2021 18:26:55
3418 forum posts
210 photos

Motorcycle wheels commonly rely on just the seals built into the bearings, even trials and scrambles machines, so you may be worrying too much.

Oily Rag15/10/2021 19:44:15
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523 forum posts
163 photos

Ian,

There are sealed bearings which are 'agricultural duty' which are designed with in built double sealing. These are commonly used on applications such as slurry pumps (slurry being a 'nice' word for the element SH 1T ) where they are exposed to slurry on one side and have the bearing element on the other side. They are also available in stainless steel for added corrosion resistance. Check out RS for something similar to stk no. 893-7458 (20 x 32 x 7) they are available in smaller sizes down to 6 mm shaft sizes.

Martin

Richard Millington15/10/2021 20:53:32
38 forum posts
Lip seal with open bearings on most OE motorbike wheel setups. Lip seal with sealed bearing will be fine.
Howard Lewis16/10/2021 16:40:31
5562 forum posts
13 photos

Before fitting the lipseal to the shaft,and housing, make sure that the shaft is lubricated, so that the lip does not run dry. If there is a keyway, ,or thread on the shaft, wrap that in masking tape before fitting the seal, to prevent damage to the lip.

Howard

IanH16/10/2021 18:21:24
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107 forum posts
61 photos

Just for interest, here is the magneto on the test car, a 1930 Family Morgan 3 wheeler. Yet to fit the cover over the bevel gear drive and fit the points cover.

img_20211011_104523.jpg

Oily Rag16/10/2021 18:22:45
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523 forum posts
163 photos

As Howard says, protect the lip during fitting.

A R23 (double lip seal ) can be run in a nominally dry situation by a smear of grease between the two lips, amazing how a little lube can last a long time.

Martin

old mart16/10/2021 21:46:29
3418 forum posts
210 photos

If you run the mag at 3000 rpm it will outlast the motor.

IanH16/10/2021 22:50:46
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107 forum posts
61 photos

The mag will be lucky to see 3000 rpm on this sidevalve, and would most likely only see it momentarily before something catastrophic happened 😬, but some or the more exciting ohv engines will rev up to 6000 rpm and even a bit beyond. A rev limiter can be programmed into the mag if required to look after the engine.

The electronic mag is designed to run clockwise or anti-clockwise, and by changing the discrete timing board mounted in a dummy cam ring, it can handle different engine types with different V angles.

Tim Stevens17/10/2021 18:28:14
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1502 forum posts

Let me guess - the mag drives a magnetic pick-up, this triggers an electronic device (in the mag or separate) which feeds a coil the secondary of which is fed to the distributor on the mag spindle. If so, I would be interested in the design of the pick-up. I have a four-cylinder version of a Lucas mag with the same mods, for my 1928 Lea Francis Meadows engine, which has served well (so far) but I hope to sort a more adjustable pick-up.

Now your question: As long as the final feed to the plugs relies on carbon brushes (as early mags and two-cylinder versions often did) there should be no problem of corrosion arising from a fully waterproof sealed  system. This is because you should have no sparks generating corrosive gases. With the later mags and more modern coil distributors, though, there is a rotating spark gap which requires the space to be ventilated. Behind the radiator is usually dry enough, but of course not in your vehicle. I add this detail for anyone else with the same concerns but different.

Do get in touch if I can help further.

Tim Stevens [bobweight@btconnect.com]

Edited By Tim Stevens on 17/10/2021 18:31:07

IanH17/10/2021 20:02:53
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107 forum posts
61 photos

There are plenty of magnetos around where the defunct magneto becomes simply a housing for a set of points. You then you have coils, or a double ended coil tucked away somewhere under the bonnet. The original magneto HT leads are either removed or tucked away somewhere, and the working HT leads from the coil(s) emerge from under the bonnet. This works but loses something in terms of authenticity.

The objective of this project was to develop a magneto that was indistinguishable from the original instrument. This means that the magneto HT leads must be real. The unit must be completely self contained, there can be nothing mounted remotely, and you can only have one wire (the original only has an earth wire) going to the magneto. The original cable advance/retard control must operate as normal. An extra rule I added in was that the double ended coil/wasted spark approach would not be used - it has been associated with carb fires on these engines.

So we have two separate coils inside the magneto body, the secondaries essentially hard wired to the HT pickups - so no distributor and no carbon brushes. There is also a PC board tucked away inside the magneto body with two more or less independent ignition circuits. A relatively small diameter shaft driven by the standard bevel gear passes between the coils and through a hole in the centre of the main PC board. The shaft terminates in the points housing.

The single wire is used to provide 12 volts from the ignition circuit.

Inside the points housing is a dummy cam ring which provides a mounting for the trigger PC board. The manual advance retard control engages with the dummy cam ring in the normal way. The trigger board provides mounting for two Hall sensors, one for each circuit. Each sensor has an associated LED indicator light to allow you to time the magneto. The Hall sensors are mounted on the PC board, separated by an angle chosen to suit the V angle of the engine. On the end of the shaft is a taper on which is mounted a component with a ring magnet that presents N and S poles to the Hall sensors.

To time the magneto, you mount it on the engine without worrying about timing, you just engage the bevel gears. You set the manual adv/retard to max advance and then turn the engine to the appropriate firing point for No 1 cylinder. You then rotate the ring magnet until it just fires No 1 (the LED indicator facilitates this). You nip the ring magnet holder up on its taper, fit the cover and then drive off 😃.

Happy to have a chat about your set up - send me a pm If you would like to have a natter.

Ian

J Hancock18/10/2021 08:14:57
781 forum posts

While driving , that 'drive shaft ' definitely needs protecting from rain,road dust, splashes ,etc.

I am sure you can devise an easily detachable cover to do that .

IanH18/10/2021 09:04:39
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107 forum posts
61 photos

There is a cover for the bevel gears and oil pump drive, here is a close up. You can also see the mag end cover in place.

79cd6a5f-c133-4891-8429-be3f5b8b0e2a.jpeg

noel shelley18/10/2021 11:36:32
870 forum posts
19 photos

Back in the sixties I worked for a company producing Luminition. This used an infra red beam and chopper arm, this gave very accurate timimg, notably between one cylinder and the next ! The transistor switching of the primary coil gave a huge spark and with a little adaptation it could be made to fit almost anything. Electronics has moved on, and Hall effect transistors now seem the first choice. Just a thought. Noel.

J Hancock18/10/2021 11:43:07
781 forum posts

Everything brilliantly accessible , if only modern cars were like that !

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