wont fire (sigh, sorry)

[daven]

dusted down the old mp5, charged battery, wont fire. just get a click.

 

the motor spins although i can grip and hold it with my hand.

 

the bevel gear can be moved reasonably easily with a pokey tool.

 

fully assembled with a multi meter in series with the fuse it'll pull over 10amps.

 

the battery reads 9.2v on an 8.4 nuprol 1.6Ah

 

before i pull it right apart, can i rule out the battery with those figures?

 

it's a t&m mp5 from about 2002 and afaik the gearbox has never been apart, was running fine when i last used it (a couple of years ago maybe).

 

many thanks

[Sewdhull]

I don't think you can rule out the battery.

 

When stalled the battery should be pulling as many amps as it ever can and 10A is no where near enough under load, my motor needed 5A just to start turning...

 

You say the motor spins. Is this out of the gearbox? Is the commutator coppery or black.

 

There are switch contacts and the copper parts on the selector plate which can corrode over time and use. 

 

Either you have too many high resistance parts in the wiring, or the battery current capacity is insufficient.

 

You might want to give it a bit of a service anyway after 22 years...

[EDcase]

I'd suspect the battery as well.  Especially if its the same age as the MP5

You shouldn't be able to hold the motor pinion

As Sewdhull said, its probably worth doing a service anyway.  Reshim etc...

 

 

Edited January 30 by EDcase

[Rogerborg]

Me three. I've popped stock fuses (20A? 25A?) with stalled motors, and now upgrade by deleting them and applying electromechanical sympathy.

 

Batteries - particularly NiMh - can look good by producing voltage without being able to supply enough current, so I'd agree with trying another one, i.e. a 7.4V lipo rather than spending more money on last-last-generation technology.

 

The other thing you can try, short of a gearbox stripdown, is shoving a long ball-end Allen key or similar up the nozzle, feel where the piston is, and see if you can get the it moving a bit. I've used that to push a stalled / locked up piston back past the release point.  Be aware that it'll then want to come forwards rather assertively.  

[daven]

the stock fuse is 15A, i'll go get another battery. cheers chaps.

 

 

[daven]

im just gunna close this up, thanks for those that replied, ive finally ordered a new battery,not before i took the c*** apart, a few things went PING! i thought HTF am i getting this back together and gaining a new respect for airsoft techs, that fiddly shit mah dayz. a mate told me how i was measuring it wrong, put the meter in parallel and saw the volts drop to 1.... yeah..ok... so yeah new battery on the way. cheers! (an yeah somehow i got it all back together ) 

[Jez_Armstrong]

So it works now? 

[daven]

On 02/11/2024 at 10:07, Jez_Armstrong said:

So it works now? 

 

well.... put the battery oh... nada... ok i'll charge it..

put the fully charged battery on.... no bueno.

hold the trigger... fuse pops. motherf....

 

so i strip it all apart... again... getting half ok at this now.

still cant see any reason for it not to move, i reassembled it without the piston and spring (i'd appreciate it if someone could tell me how to release the metal tab that appears to hold the spring in) and clack clack whirring of gears... so... i dunno.

 

anyways, i remember this guy... what he said had always stuck in my head 

On 30/01/2024 at 18:14, EDcase said:

its probably worth doing a service anyway.

 

 

 

whilst i have no idea how to judge if it needs shimming it's barely done a thousand bbs i reckon but the lube could be getting a bit sticky, so i cleaned it all up and read you need two different types of lube so i used butter and old engine oil. 

 

i've just reassembled it, pulled the trigger....

 

fuck me dead and bury me pregnant .. it works!  

 

i guess it was just the old sticky lube. 

 

it's probably only firing 3fps but its a start.

[EDcase]

Congrats.  Well on the way to becoming a tech 😜👍