Giss system ratchet wheel

[HW777]

Just a heads up for a Giss system ratchet wheel, on flea b section Diana.

I'm sure there was someone looking for one a while back

[ptdunk]

That was me, thanks for the heads up, I’ve just ordered it.

The seller has some interesting bits, including a Diana parts box and Gun layer teacher rubber tank.
Much appreciated!

Matt

[Benelli B76]

They are quite strong and only seem to lose a tooth when the pistol is assembled with the piston racks slightly out of alignment. One good test is that the gears should just fall into place under no stress when the back piston is in its correct position before the back cap is replaced I have seen the gears forced into alignment on the two racks.

Baz

[ptdunk]

They are quite strong and only seem to lose a tooth when the pistol is assembled with the piston racks slightly out of alignment. One good test is that the gears should just fall into place under no stress when the back piston is in its correct position before the back cap is replaced I have seen the gears forced into alignment on the two racks.

Baz

I resealed my 60T and had it set up like that, the cog could just drop in and out. However after couple of hundred shots there was some graunching so I took the caps off and one on the cogs had a broken tooth and the ratchets were no longer precisely in line. Best guess is that the new piston seal or buffer settled a bit after use or compressed and took the ratchets out of alignment.
I might give it to someone to set up perfectly when I get the new cog as I love the rifle and it’s in really good condition.

Cheers,
Matt

[dvd]

I resealed my 60T and had it set up like that, the cog could just drop in and out. However after couple of hundred shots there was some graunching so I took the caps off and one on the cogs had a broken tooth and the ratchets were no longer precisely in line. Best guess is that the new piston seal or buffer settled a bit after use or compressed and took the ratchets out of alignment.
I might give it to someone to set up perfectly when I get the new cog as I love the rifle and it’s in really good condition.

Cheers,
Matt

I'm pretty sure the mod 60 had an annular groove at the bottom of the compression cylinder.
If the crud and remnants of old seals are not scraped out of the groove, the piston will not bottom out against the cylinder's end as it should, with the result that the piston's forward motion is braked by the gears rather than the piston coming to rest against the cylinder bottom. The gears and the whole system are not designed for this stress and will fail.

I have many different models of Diana GISS guns which I service myself and I never do up the gear covers so tight that I can not undo them by fingers when the gun is uncocked since if they tighten up and can't be turned easily while uncocked it means that the gears are loaded and it's time for new seals and shims.
The gears just synchronize the the two pistons and are idler gears, they should never be loaded at any time except during the cocking stroke.
HTH.

[Garvin]

I'm pretty sure the mod 60 had an annular groove at the bottom of the compression cylinder.
If the crud and remnants of old seals are not scraped out of the groove, the piston will not bottom out against the cylinder's end as it should, with the result that the piston's forward motion is braked by the gears rather than the piston coming to rest against the cylinder bottom. The gears and the whole system are not designed for this stress and will fail.

I have many different models of Diana GISS guns which I service myself and I never do up the gear covers so tight that I can not undo them by fingers when the gun is uncocked since if they tighten up and can't be turned easily while uncocked it means that the gears are loaded and it's time for new seals and shims.
The gears just synchronize the the two pistons and are idler gears, they should never be loaded at any time except during the cocking stroke.
HTH.

Great advice!

[Ryde]

If you need spares, this is a great shop

https://www.waffencenter-gotha.de/sh...8_265_250.html

I have a 65 and a 75 that's going on the table this winter for new seals

[ptdunk]

I'm pretty sure the mod 60 had an annular groove at the bottom of the compression cylinder.
If the crud and remnants of old seals are not scraped out of the groove, the piston will not bottom out against the cylinder's end as it should, with the result that the piston's forward motion is braked by the gears rather than the piston coming to rest against the cylinder bottom. The gears and the whole system are not designed for this stress and will fail.

I have many different models of Diana GISS guns which I service myself and I never do up the gear covers so tight that I can not undo them by fingers when the gun is uncocked since if they tighten up and can't be turned easily while uncocked it means that the gears are loaded and it's time for new seals and shims.
The gears just synchronize the the two pistons and are idler gears, they should never be loaded at any time except during the cocking stroke.
HTH.

Thanks David,
Didn’t know about the groove in the cylinder.

I’m pretty sure the cog caps were only finger tight when I removed them, but maybe they were less than totally loose. The piston teeth are definitely unbalanced though, I can see through the cap cog holes.

So if I re-do the setup with the new cog, and the caps are easy to turn when uncocked then by definition they’re not under load?
Checking every now and then could be a good way to keep an eye on it, and at least the seals should all have settled already.

I do love this gun but it’s frustrating that this can go out of whack without any outward evidence and ruin the gun (bit like a leaky anschutz 150) no wonder the FWB 300 series were so popular.

Cheers,
Matt.

[dvd]

[QUOTE=ptdunk;8268253]Thanks David,
Didn’t know about the groove in the cylinder.

I’m pretty sure the cog caps were only finger tight when I removed them, but maybe they were less than totally loose. The piston teeth are definitely unbalanced though, I can see through the cap cog holes.

So if I re-do the setup with the new cog, and the caps are easy to turn when uncocked then by definition they’re not under load?



Hi Matt,

Exactly, do not use any tools to tighten the gear caps, just snug them up finger tight. Start by removing the gears then thread the gearless caps on again to see and feel that the threads on both caps and cylinder are clean and rotate smoothly without any binding. The threads are very fine and easily bind if not absolutely clean. That way you can be sure that if you feel any binding when you rotate the caps with the gears installed, it will not be due to debris on the threads and you can get the correct gear to rack position by using a different size shim to alter the position of the rack in relation to the linear position of the gear wheel's hole.

The most important thing to keep in mind with all GISS systems is that the compression and the dummy piston must always bottom out at their respective resting place exactly at the same time. That ensures the longevity of the whole system especially the racks and gears.

Cheers.