Blown Fuse after upgrade, MP5 RAS

[Corey Darling]

Hello,

This is what I've recently installed in my TM mp5 ras. This is my second upgrade attempt on this gun. First one didnt go so well, will explain further down.

PDI 150%
SystemA Steel Torque Up Gears (non-helical)
Gaurder Steel Pinion Gear
Metal Bushings, Shims

Before reassembly, i checked all three gears for movement, including with the Bevel gear's anti reversal latch. and all seemed fine, the only thing That has me a bit concerned was that there was a tiny tiny amount of side to side movement on the bevel gear (i couldnt get a good shim combo that would still allow the whole system to spin freely ) but was hoping that once the motor was in and up against the bevel,it would keep it in place.

So, got the gun back together, charged the battery, connected the motor up correctly to +/-, and set it to Semi auto. i adjusted the set screw on the motor plate so that i couldn't tighten it any more (assumed the motor was tightly meshed with the bevel gear.) So i backed it off a few turns.

Please note: This is the second attempt at upgrading this gun. My first try, i only upgraded the spring and bushings. But while i was doing this, I unknowningly lost the Motor adjustment plate for the setscrew. When i first fired the gun it stripped the bevel and the pinon, hence the steel gears this time). Since, I have made up my own plate out of some thin metal i had kicking around. its 2 mm thick and fits perfectly in that hole on the motor receiver plate.

Well, I tried to fire.... Nothing happened. Tried again.. heard a pop and knew the fuse had blown.

What could be causing this? I was thinking that the motor was too tightly meshed with the bevel, so im going to get more fuses and try backing it off some more.

Another note, I used lithium grease on the gears as was explained in the tutorials i followed, including the new on on www.mechbox.com But how much is too much? I made sure that all teeth had at least a small amount on there. Could this be slowing down the system? It felt like it when i tried spinning it by hand before resembley, but it soon freed up.

I also noticed that the stop latch appeared a bit lower than were it should sit in comparison to the bevel gear, so i put a shim inbetween the spring and the latch hopeing to move it up a bit.

If this doesnt work for me i might just give up on upgrading and get a new gun. I cant afford to keep buying 110$ gear sets everytime it doesnt work out :S lol

Any help or suggestions would be much appreciated.

Thank You

Corey

[Mantelope]

You probably shimmed it too tight, preventing gear movement. take everything out of the mechbox except for the bushings, gears and shims, stick your finger in through the cylinder hole and try to turn the sector gear. It, and the other two, should move freely.

[Corey Darling]

Hi Harley,

Unless something changed while i was assembling the rest of the mechbox, the gears should still be okay.

I checked the gears in the way you mentioned and they moved freely, i did so with the trigger and the antireversal latch in place also and it still moved freely.

Thanks for the suggestion, i'll check that again as a last resort, i'm getting tired of taking this thing apart lol

Corey

[CDN_Stalker]

Any time an upgraded spring gets put in, the stock 15A fuse needs to be replaced with minimum 20A fuse. That's what happened, you didn't replace the fuse. Canadian Tire is a good place to buy them, make sure you buy the 1 1/4" fuses, and if you can't find 20A, 25A or even 30A will do the trick, just reducing the level of protection (know this, the fuse only protects the wiring to prevent it from bursting into flames).

[ILLusion]

A properly shimmed gearbox can easily handle 400+fps springs without having to replace the fuse.

I've never upgraded the fuse in any of my guns.

[Corey Darling]

Hey Stalker

Yeah, will do. I was going to get a bunch of 15Amp ones and a 20Amp one to see if that is the problem.

Thanks for the info, that made my day lol I didnt realize that was a requirement. So instead of a bunch of 15's ill do as you suggested and try 20 and up.

Thanks very much
I'll let you guys know how it turns out.

Corey

[CDN_Stalker]

Originally Posted by ILLusion

A properly shimmed gearbox can easily handle 400+fps springs without having to replace the fuse.

I've never upgraded the fuse in any of my guns.

Interesting.

Corey, yes, give that a try, seeing as how you need a new fuse anyways. And don't give up on your gun, try the shimming job again. Take out the piston, spring, cylinder and screw the mechbox back together with tehe gears in there, and see how well the spin. Chances are you only held the halves together with your hand and shimmed for that, then put the screws in and it jammed up too tight. BTW, there's nothing wrong with stock TM gears, they are pretty decent quality, so you can go back to those in a pinch. And the PDI 150% springs should be avoided these days since they are shit quality control. I think that is your biggest problem here. Next time you have it out, tell me if it's gloss black or a dull blackish brown colour. Then measure the length of it. I got lucky once and got a good PDI 150% spring, measured 6 3/8" long (this is the key, because that's what I figured out the PDI problem is), has the dull black/brown colour, and put out 350fps in my MP5. I've had other PDI 150% springs come through my bench and they all are too long (all the way up to 7" long in some cases) and the wire is thicker gauge (like 1.5x thicker); some are impossible to install (aka will blow the mechbox in no time) and others are difficult to install and put out well over 400fps.

[Corey Darling]

I hope I shimmed it okay, like I mentioned, this is my first attempt.

All seemed to be spinning freely when checked, and i tried to leave a very thin gap between gears. But like i said earlier, the only gear that was actually a bit loose was the bevel, If i had another one of those very thing washers (guess its .2mm) that would do the trick, but i didnt have anymore with the Gaurder bushing kit i got.

I had 5 of what i guess are .3m shimms, one .5 mm shim, and one .2mm shim.

i used the .2 on the bottom of the sector gear, .3's on the both sides of half gear. and one .3 on the top of bevel gear. No shim on the bottom of the Bevel gear by where the teeth mesh with sector. this is where i would have liked to put another .2mm and this is why there is a bit of slop.

I put the .5mm shim inbetween the spring and the bottom of antireversal latch to bump it up a bit.

Corey

[CDN_Stalker]

I just editted my post while you were typing Corey, you should give it a read.

[ILLusion]

The key to testing shimiming, like Stalker said, is to do it with the gearbox screwed together. Simply holding the halves together with your hand aren't sufficient.

[Corey Darling]

I tested the shims by doing both, holding and screwing the case shut just as Mechbox.com tutorial showed. in both cases they spun fine. It wasnt until i tried putting in that second shim on the bevel gear that it locked up, thats why there isnt one on the bottom, and therefore, the small amount of side movement.

Im at work right now, will run out at some point to try new fuses.

As for the spring. If these fuses dont work ill check the PDI one like you mentioned. if i remember correctly, it was black finish

Corey

[Mantelope]

Only other things I can think of are the motor was too tight against the bevel gear, or it was in backwards. I know you checked for those things, but hey, you never know...

[Corey Darling]

Thats true lol

yeah i was thinking the motor was too tight also. was going to be the first thing i tried after the new fuse. i'll double check the motor wires also

PS. i also installed a BB metal spring guide.

Corey

[CDN_Stalker]

Originally Posted by harleyb

Only other things I can think of are the motor was too tight against the bevel gear, or it was in backwards. I know you checked for those things, but hey, you never know...

Seriously, there was one occasion I put the motor in the wrong way and the gun wouldn't cycle, then I found my mistake after a quick search.

To err is human.................

[Corey Darling]

Well, off to get some fuses, will let you guys know how it turns out

thanks again

Corey