Author Topic: 37 600 aero oil levels  (Read 2662 times)

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Offline polly

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37 600 aero oil levels
« on: 29 Sep 2015 at 13:59 »
a question please  for our learned members!
 the oil capacity in the crankcases is 460ml, the weir hole from the crankcases to the timing chest is 40mm from the bottom, ! reading the article by Doug on the a31 indicates the level should be minimal, is mine right as the weir hole seems to be original! photo to follow! regards david

Offline polly

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Re: 37 600 aero oil levels
« Reply #1 on: 29 Sep 2015 at 14:14 »
pic

Offline Doug

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Re: 37 600 aero oil levels
« Reply #2 on: 29 Sep 2015 at 17:18 »
David,

The crankcase would only have a small amount of oil present, as the crankshaft assembly would whip most of it into a mist. This mist is blown over to the timing side through the timed breather valve behind the crankshaft pinion. [Addendum; see subsequent post regarding rotary breather.  -Doug  29Sep15] The only picture I have inside the timing chest on my 600 Aero has the gears in place, so I cannot see if it has a hole drilled through 40mm off the floor of the crankcase, nor can I remember. But I cannot see the point of having such a hole, in conjunction with the timed breather. Perhaps someone else has a bare casting that can verify.

In the timing chest proper, you will have two oil levels. The rear compartment is about 40mm deep, and is enough to submerge the rim of the lower timing gear. Any excess spills forward over the weir into the front compartment. There it is collected by the pickup from the oil pump (scavenge), and so would have very little present.






-Doug
« Last Edit: 29 Sep 2015 at 18:55 by Doug »

Offline polly

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Re: 37 600 aero oil levels
« Reply #3 on: 29 Sep 2015 at 18:12 »
many thanks Doug, I can see what you mean by the timing chest having two compartments, thank you, as to the timed breather, I haven't got one! and there isn't one described in the 38 parts list!! crankcase compression is relieved via the main bearing slot as per your/mine pic, mine had a large oil throw washer covering the inside timing side bearing, mentioned in the parts list, which I believe is wrong as it would obstruct the breathing process through the bearing ? regards David

Offline Doug

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Re: 37 600 aero oil levels
« Reply #4 on: 29 Sep 2015 at 18:51 »
David,

Oops, looks like I need to eat my words.

Some of the engines did have a timed breather in conjunction with that arc shaped slot. Such as the 1925 250cc models (see picture of 250cc crankshaft).



But it has been so long ago, I could not remember if the 600 Aero has the rotary valve or is it was omitted; and mistakenly assumed it did because of the slot. I just whipped the timing cover off mine, and see no rotary valve. Also the extra breather hole is present, 40mm off the floor of the crank case chamber, just like yours. Unfortunately the angle is too acute to get a photograph.

So either the hole is to supplement the breathing through the curved slot, or supplant it. If they used a oil thrower on the timing side, then that suggests they wanted to supplant it. Why, I have no idea. Normally I would expect a thrower just on the drive side to make life easier for the felt seal. It was standard design with the Dougies for the oil to end up in the timing chest eventually, so why block its path? I see what you mean in the 1938 parts list, an oil thrower is clearly mentioned for the timing and flywheel end of the crankshaft. 

-Doug

 

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