Adding a second pin to the 2nd gear detent

Dear List,

The problem of even good Moss gearboxes sticking in 1st gear is well-documented in this Form.

I disassembled mine, and indeed found that the single rivet preventing the1st gear getting locked is chewed up. It’s really a poor design my Moss, as there is only one of these rivets and it gets the push pressure of the lever in a minuscule shear surface.

I plan to install now a new steel rivet, but wondered what would prevent me of drilling a further 4.9 mm hole on the opposite segment of the gear and adding a second rivet, to better spread the shear force?

Edit: this is the rivet I mean:
image

Any advice?

Best,

Lluís

Drilling that second hole will be a challenge in that case hardened steel. Diamond bit and lots of lubrication? And then you’ll need to thoroughly flush out the gearbox to remove any filings that get away between drilling out the old rivet and the second hole.

Is that rivet mild steel and peened in place?

Thanks for the reply Nick: I plan to use high strength blind rivet nuts of steel. They are not pinned but I could quench them after fitting quite easily. Frankly the original rivet was vey soft, it drilled easily.

I had not thought about the fact that the gear could be very hard indeed… I got diamond coated drills, but will this be enough? Not sure indeed…

I’m not sure if the geometry of the inner surface of first gear is set up to collide with a second rivet or not. There needs to be room to slide over it, then a landing to bump against it. Mine is apart on the bench if you want me to check. But as Nick says, the gear is unbelievably hard. You’ll wear out 50 bits trying to get through it, plus if it’s not apart you’ll contaminate your box with metal filings.

I’m not sure what kind of steel rivet you plan to install. As Bill @angelw can attest to, there is no room at all for a layperson to use a hammer or squeeze type rivet without an expensive specialized tool as there is only about a 1/4" of free space under the rim of the gear. They must have had a very slim jawed squeeze tool in the factory. If your plan is to use a steel pop rivet, I suspect it will fail faster than the original one did due to being hollow once the nail is ripped out.

I’m planning to use these cool drive rivets, then knock down the head with a mill. Given that the drive pin is solid steel, it should be much stronger than a pop rivet.

Hanson Drive Rivets

Ultimately the easiest solution is what @Ray_Livingston did, install a nylon spacer on the guide rail for the fork to act as a bump stop.

Many thanks Monica,

My plan was a steel pop rivet (Edit: my gearbox is appart and indeed I plan to use the exact river type that Hansom-Drive sells, they mechanically screw to the gun and are hammered both ways). I will see whether I can install an opposite one at 180°, it will indeed depend on getting a proper diamond coated drill.

The nylon solution is 90% optimal, there is play in the fork for sure and it may limit gear contact, but I will also do it: Nylon or bronze should do IMHO.

Thanks a lot.

Lluís

Could you link to the type of rivet you’ll be using?

I’m thinking of using both rivet and washer, with the washer being a backup that hopefully never gets used. I’m also planning to machine the side of the rivet head to match the dimensions of the old rivet head, and create a flat bump stop rather than a round conical one. Greater contact area should make it much less likely that the gear nibbles away at it until it runs over.

Erika: the day after tomorrow my rivet and gun arrives and i will post pictures.

I’ve been through this.
The 2nd synchro sleeve is harder than woodpecker lips.
And you have to carefully calculate exactly where to put the hole.
And I don’t know that the 1st gear wheel has two relieved teeth inside, I think it’s only one.
Read this.
https://www.jag-lovers.org/xk-lovers/library/gearbox_reilly/gearbox_reilly.html
Mine has been fine with only one stop pin. It had none originally.

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Rob many thanks,

You were certainly missed in the forum the last days.

I will post pics later: i ended up buying steel rivets, without a center pin and will also add a washer to the fork. My box got stuck three times in 5000 km, and i could get it out just by poking the lever a bit, but since it was out for the coutch job, why not do the full job.

Best regards also to Erika (will post the rivet pics as promised) and thanks all for the advice.

Lluís