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brucey

Tiger Cub Modified Gearbox Cover

33 posts in this topic

I have just finished building my dream Armac Cub but am slightly frustrated at not being able to stop a minor oil leak from the gearbox side. 

I cured the clutch side by fitting a belt drive primary and diaphragm clutch :)

I had a spare gearbox cover, a lathe and a mill so decided to try the Armac conversion and do away with the outer cover, however,  I only have a photo to work from.  I don't have access to ally welding equipment so am trying to avoid welding if possible.

I have machined the flanges off the edges of the side cover, modified the case for a clutch lightener (I'll be using my original Armac clutch lightener on the bike), machined the selector housing for the modified seal plate and made the vent at the bottom into an M5 drain hole.

I intend to make an extended camshaft bush from Phospher Bronze (with an open end so I can ream it 5/8") then make an aluminium cap to push onto the outside end sticking out of the side plate to seal the end and make a protective cover.  This way I can take it apart again at a future date if required.

I'm a bit stumped with the kick start side of things as I have no information apart from the attached photo.  I was just going to make a large ally washer to simulate the now missing outer case but I'm not sure if I should make a cover to protect the return spring.  I would also like to incorporate some form of oil seal as the kick start shaft has the potential to leak oil.

Even if fitting the modified cover doesn't cure the leak, at least I should be able to see where it's coming from!

Any help or advice appreciated.

 

Bruce.

 

Armac Engine RH Case.JPG

Armac Engine RH Gearbox Cover mod.JPG

Edited by brucey
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These 2 were at the Yorkshire classic trial club, boxing day trial, thought they looked trick P1010125.JPG

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I prefer it with the cover on easy to keep clean and a bit of protection still good luck to you 

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I'm with Stan on this....can't see any advantage with the cut down case....just seems like a lot of work for no gain and not so good looking in my oppinion too.

 

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Stan & Bashplate, I appreciate your comment but it is an 'itch I have to scratch' :)

I'm modifying a spare gearbox side plate that needed the selector shaft location hole repairing. (now featuring a steel bush). 

It is one of those projects that suits my abilities (Ex Toolmaker from the 70's and currently a Design Engineer working on Hitachi trains).   So it ends up as a nice little project for my shed.

If I don't like it, I'll simply put the existing bits back on. (as the photo)

It still begs the question, where does everyone else get their modified gearbox side plates and what is done to them. (there seems little point in reinventing the wheel)

By the way, I have no interest in making any more after this one!

I am a little surprised that no one is offering a slightly better looking new CNC machined part that has all the oil leak and other mods incorporated.

 

Bruce.

 

Armac Cub running in 060917.JPG

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Today's Progress:

 

Armac case progress 1.JPG

Armac case progress 2.JPG

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Keep up the good work, of course you deserve a modified side plate. Simply because it can be done (and make your bike look even more works)!

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On ‎31‎/‎12‎/‎2017 at 6:12 PM, shakennstirred said:

These 2 were at the Yorkshire classic trial club, boxing day trial, thought they looked trick P1010125.JPG

Did you happen to notice if you could see the kick start return spring on these bikes?

Bruce.

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Brucey if you look at a Villiers engine the road version has a full side case similar to a Cub but on the competition model it was cut off after the mag case leaving the gearbox side cover exposed as you are doing with your own engine. Villiers fit a pressed metal cover over the spring, maybe you could make something like this?

 

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Trialsrfun,

Thanks for the info. I think I'll buy a sprare kick start return spring and see if I can turn a suitable ally cover on my lathe. 

I'm also looking to put some form of seal around the kick start shaft (7/8" diam). I can't find an oil seal with a small enough od (needs to be 1"). So I'm currently looking at O rings. 

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Can't you machine the inside of the side cover to take a thin oil seal? It doesn't "have" to be on the outside.

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2 hours ago, oldaz said:

Can't you machine the inside of the side cover to take a thin oil seal? It doesn't "have" to be on the outside.

Oldaz,

Nice idea but I have looked at this option and the only oil seal I can find at the moment is 7/8" ID x 11/4" OD x 1/4" wide.  Unfortunately that won't leave enough material around the kick start spigot casting at either end!

It's a bit of a shame as I was going to buy a cheap boring head for my mill to machine the recess!

I need to check if the cover will fit on my lathe face plate this evening.  If I can, I may be able to design a spring plate retainer and combined oil seal assembly to fit in a recess machined into the outer end on my lathe.

 

Bruce.

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10 hours ago, brucey said:

Oldaz,

Nice idea but I have looked at this option and the only oil seal I can find at the moment is 7/8" ID x 11/4" OD x 1/4" wide.  Unfortunately that won't leave enough material around the kick start spigot casting at either end!

It's a bit of a shame as I was going to buy a cheap boring head for my mill to machine the recess!

I need to check if the cover will fit on my lathe face plate this evening.  If I can, I may be able to design a spring plate retainer and combined oil seal assembly to fit in a recess machined into the outer end on my lathe.

 

Bruce.

Don't rely solely on imperial measurement seals, I've found quite often you can get a metric seal that will do the job and solve a problem that's been around for many years. I'm guessing you've already looked at machining the outside of the boss off and replacing it with a bolt on unit incorporating a seal, otherwise I hope it fits on your face plate.

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Yes, I also looked at 22mm ID seals (7/8" is 22.23mm) but still couldn't find any with a small enough OD (needs to be 25mm max) which is really 'O' Ring territory.

Unfortunately it doesn't fit on my face plate :( so machining an 'O' Ring groove into the boss becomes difficult.

I know Bob at UPB adds weld to the boss (I'm assuming he fills the flat on the outside of the boss) to allow an oil seal to be fitted.  But I have never seen this mod.

I'm waiting for a spare kick start return spring to arrive so I can see what space I have available and decide my options. 

I need to balance how much effort/risk I'm going to put into modifying the side plate to prevent what is probably a very small oil leak!

I made the cam shaft bush outer cover last night and that looks great. :)

I've made the schoolboy error of starting to polish out the casting marks and now don't know where to stop!

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Today's Progress: (Just in case anyone is still interested!)

I managed to source a metric oil seal ID 22, OD 28, W 4. (Thanks for making me look again Oldas:))  So I ordered 2 off. 

I made a 1:1 paper template and placed on the kick start spigot, it will just fit. (see photo)

If necessary, I will get a blob of ally weld put on the end of the flat but I'm not too bothered if the seal OD just breaks through.  I will need  to buy a cheap boring head for my mill or get a 28mm cutter to modify the housing to accept the seal.

I fitted the Ally end cap I made to my modified design cam bush which all looks o.k.  The cover is a light press fit over the bush and I may loctite it in place if I need to remove it to open out the bush on final assembly.

I couldn't resist a little go with my polishing wheel.  I think it looks o.k.

My next job after the kick start spring and oil seal arrives will be to check this part of the assembly to see if I can design and make some form of cover.

As the 22mm oil seal ID is 0.23mm smaller than 7/8", I will need to check how freely it turns on the kick start spindle.  As it isn't constantly rotating, I can't see this being a problem as I can always make the seal ID a bit bigger if necessary.

Armac case progress 3.JPG

 

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