Housing modification for moving bottom bevel gear

[Bevel bob]

The ruined bearings would not "fall out" but they could not survive the axial loads from the cam actions which they would have to carry if the bottom of the "bucket " was not there. However thats not a problem here is it. It does however give some understanding of why the big shim between the "bucket " and the tunnel housing is important and why it must be nipped down and the gasket thickness to be just right to allow this. Perhaps its one of those situations where a BSA Gold Star type of "peelable" head gasket would be helpfull. I had to pack the shim up with a paper gasket to get a nip. Without this the whole assembly is just free to jump up and down when hot.I was surprised to find this on my motor, a tap on the underside of the bevel gear changed the mesh with the crank bevel.

[BDang]

Bob,

I know exactly what you meant about the gasket thickness potentially interfere with the bearing OD spacer. I would think in this case a better solution is not to use any paper gasket and use Toyota "Form-in-Place" gasket sealant instead. This stuff is used by Toyota on the oil pan without any paper gasket. Absolutely zero oil leak or dirty pan even after 300K miles on the car. I have no idea why other car manufacturers continue to use 100 years old technology "paper" gasket on the engine oil pan, and it would leak with age.

http://www.brandsport.com/toy-00295-001 ... AtaI8P8HAQ

Regards,
Brian

[Bevel bob]

This approach can work fine and is used by some very competant engine builders. The gasket did perform another essential function in that it allowed the housing to be pulled down tightly without getting distorted. If "GOO" is used then some form of packing is needed (shim!) at the fixing points to level things out and care to keep the goo from going where its not wanted.

[Rocla]

Hello both,
To make it clear, yes, as you can see on my picture, the part named "sleeve" on the attached drawing by BDang is not modified at all. It is only the engine housing (the right case) that is milled. The sleeve is strongly stuck inside it.

Dare I say it, such modification would have been embedded in every engine. For me, it looks like an design error...

[BDang]

Hi Rocla,

It would be nice that the factory designed the right side case to allow removal of the lower bevel gear, but if I were the designer I would prioritize a strong case to strongly hold the bearing "sleeve", which is pulled and pushed by the bevel during acceleration and deceleration. The need to remove the lower bevel only when it was damaged, as in your case. I would reason that if the bevel was damaged then in most cases there would be a lot of metal bits circulating inside the engine, and so it needs to come apart for cleaning and inspection.

I wonder with the missing milled piece, would it weak enough to develop a crack under the push/pull force?

Regards,
Brian

[BDang]

Bob,

"The gasket did perform another essential function in that it allowed the housing to be pulled down tightly without getting distorted."

This is a very tricky design, that the flange needs to compress the gasket first for a tight seal before making contact to the big bearing-spacer. This requires a very special gasket thickness per application. I would think more people try to torque the two screws for a no oil-leak resulting more distorted flanges. I don't have the flange front of me, but I think the screws are not too far a distance from the force applies on the big spacer, and so a proper torque enough to lock the screws from backing out, won't distort the flange.

Metal cannot be used for packing since this would interfere with the bearing spacer dimension. As about the goo going anywhere, only a narrow bead of goo, with a slightly thicker than the original gasket be applied around the periphery of the flange needed. It should not go anywhere even without the packing.

Regards,
Brian

[Rocla]

Hello,
Just a better picture of the mod.

[img]

ScrBevel16.jpg

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