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View Full Version : New metal bushings = shimming :(



ichainsaw
02-08-2008, 09:44 PM
Alright, I am finally installing those metal bushings I received...and now I must shim them. I've read up on the subject:
http://www.858airsoft.com/upgrades/shim.html
http://pageproducer.arczip.com/daedalus03/shim.html
http://www.mechbox.com/site/mechbox-upgrades/version-2-mechbox-upgrade-video.html
And I have some questions...on one side of the mechbox shell (the side without the selector plate, the one without anything on it) the bushings seem to be a tight fit. I have to click them in, where as the other side they just fall in nicely. Is this a problem? Should I try to widen the bushing holes on the other side so they both fit equally? I'm using echo 1 bushings, and I heard that I can take a pair of scissors and twirl them in the hole to make it bigger.
Another thing: I'm currently shimming the spur gear (the first gear I'm starting out with) and I find that when I put the screws in to test it, it doesn't even spin. It hardly even moves. Is this a problem with the bushings on the "bad side" of the mechbox shell? Or is this a shimming problem?
And another thing: once the shimming is complete, is something I should be looking for. Should the gears move easily and freely?
If you want to join Chat (http://lonestarairsoft.com/forums/chat/flashchat.php) and help dynamically that would be GREATLY appreciated.

Update: Spur gear is shimmed. It spins sexy smooth without any shims on top but with one .3 on the bottom. No rubbing and it is stable. Tested multiple times with the screws in.

Update: I believe the Sector gear is now shimmed...It is moving smoothly and is the correct distance away from the Spur gear. I put one .3 under it and a .2 under it.

AustinWolv
02-09-2008, 12:01 AM
Late reply but......


I have to click them in, where as the other side they just fall in nicely. Is this a problem? Should I try to widen the bushing holes on the other side so they both fit equally?
You want them to fit into the mechbox holes tightly, so they don't spin. If one side spins, use some glue only on the outside surfaces of the bushing to adhere them to the mechbox shell. Always ensure bushings are seated completely in the mechbox shell.


it doesn't even spin. It hardly even moves. Is this a problem with the bushings on the "bad side" of the mechbox shell? Or is this a shimming problem?
Shimmed too tightly.


Should the gears move easily and freely?
Yes, they should spin smoothly and cleanly with each other. You don't want side-to-side movement.

ichainsaw
02-09-2008, 12:19 AM
Thanks for the reply, I think I have the hang of this to some degree. I found the goal I am supposed to make happen and I am doing it. Did that last sentence make sense? Probrobly not, laying on the floor screwing and unscrewing gearboxes and adding tiny metal spacers does nothing for your grammar.

Ok I have all the gears in and running smoothly...but I have a problem (I'm contradicting myself now) They will smoothly spin up until a certain point then stop, and then I will try to spin them the other way and they stop the other way too. It seems a couple of the bushings are spinning while the others stay in place. I'll try to re-seat them and see if that fixes the problem, otherwise I'll use some glue or something.

I reseated the bushings so they do not spin, and the problem still persists. I spin the gears and they seem to get caught on something. I'm going to do some further inspecting in a minute...wait...I want to go to sleep now.

Update: the problem is with the sector gear. I narrowed it down to that. It only occurs while both sides of the case are on...Could it be the semi-auto catch thing that is snagging it? Is it supposed to be loose? I can jiggle it with my finger. Is that bad? I can't see what would catch it on the other side of the case.

ichainsaw
02-09-2008, 08:17 PM
Ok now I have a problem. I start with the spur gear; I add a .3 shim to the bottom. It clears the mechbox floor fine and does not rub on anything. I add the sector gear with a .3 also; It rubs the spur gear a bit. I add a .1 shim to it. It clears the spur gear...but alas, the knob that drives the tappet plate catches on a rail of the upper gearbox shell, I try to shim lower and the spur gear touches the bottom of the mechbox and the other bushing...I add shims to the top and it makes it too tight. Catch 22 anyone? Nothing is supposed to touch the outside of this rail, and it doesn't really even do anything...and It's that .1mm of metal on that rail that is holding me back. So I'm going to take a screwdriver to it and shave it down...

Nevermind, it would take A LOT of shaving to get past that...I'm going to shave .1mm off of the bevel gear bushing hole. Then I could shim lower to avoid the rail.

Actually screw it. Just screw it. The skirmish is tomorrow and I am not going to mod my damn mechbox over 13 buck bushings. Is this a problem with my bushings or my mechbox? I'm using echo 1 bushings and guarder shims. What are the advantages of metal bushings anyway?

Actually, actually scratch that last part. It is working now. I think I have a safe distance between the gears now...everything spins like a dream now, I don't hear much gear touching.

AustinWolv
02-09-2008, 09:44 PM
What are the advantages of metal bushings anyway?
They don't melt due to generated friction with the gear axles, and they don't deform from the radial forces.

ichainsaw
02-09-2008, 09:47 PM
They don't melt due to generated friction with the gear axles, and they don't deform from the radial forces.
Oh, so do they include regular nylon bushings in the first place? just to mess with you? Or are they that much more expensive per gearbox? Well, this is the price I pay for wanting that stupid folding stock. The rest of the echos come with metal bushings. Ah, well...I hope I can get this working before sunday.

AustinWolv
02-09-2008, 09:51 PM
Oh, so do they include regular nylon bushings in the first place? just to mess with you? Or are they that much more expensive per gearbox? Well, this is the price I pay for wanting that stupid folding stock. The rest of the echos come with metal bushings. Ah, well...I hope I can get this working before sunday.
Well, assuming it had a stock spring (M80), that spring isn't very strong and doesn't cause the same radial forces on the bushings.

ichainsaw
02-09-2008, 11:03 PM
Well, assuming it had a stock spring (M80), that spring isn't very strong and doesn't cause the same radial forces on the bushings.
Oh ok. Ok so I'm shimming the sector gear and I have it nice and loose, it runs extremely smooth but it wiggles. When I shim the top to stop the wiggle it makes it run less smooth. What should I do?
Ok I got it to wiggle less, and still spin great. I don't think I can get it to be 100% perfect, but I think this is as close as I can get. Is this ok?
Update: Score, Sector gear is shimmed. I added a .1 on top (apparently I mismeasured one of the shims, it was a .2 not a .1
I'm pretty sure my gun has a m100, it pushes 340-350 regularly chrono'd.