Rewiring an MG34

[renegadecow]

Man, this thing blows. They go through all the trouble in making a propriatory gearbox, even though an M249 gearbox would perfectly fit, and the front section is no thicker than your bog standard V2. Then some galoot puts in a heavy metal pisto head with bearing without so much as radiusing the cylinder window.

[renegadecow]

And the buck converter which I thought was ok decided to quit. It may have been my fault in part as I had mistakenly wired the override switch to send a negative feedback into the gearbox, putting it in reverse. While the buck converter worked the right way in either mode, I think that feedback loop put the gearbox in series which upped the amperage and killed it. Then again, the thing wasn't really working properly to begin with as the voltage output selection didn't work. But for the time it was running parallel with the gearbox it was working splendidly and with an Atomic Tuned Tamiya motor. So now I have to get a new buck converter and put in a two way switch to make the override option completely independent this time.

[ED-SKaR]

You are seriously overcomplicating this...

[renegadecow]

You mean with the buck converter? The only complicated part is the fact that locally available ones are the size of a fist for some reason. Already ordered the usual small ones from China. And the two way switch for manual is only really intended to cut the circuit leading to the gun so it won't feedback anymore.

[3vi1-D4n]

yup I did the same job with a 5ohm 15W resistor.  Sure it won't feed as fast with a 7.4v but my MGs run on 11.1v @ 500fps anyways

[renegadecow]

Problem is I can't find strong enough resistors locally. Went to the electronics shop and they only had the tiny ones like these:

[Stuey]

Put loads of them in parallel?

 

I don't know what feedback you're talking about, a buck converter should have two input terminals which you connect in parallel with the trigger switch and two output terminals which you connect to the boxmag motor. Add the 'wind' switch in parallel with the trigger switch. Job done.

[Stormin]

I live right near the Rapid Electronics warehouse. If you make an order (over £5) for trade counter pickup I can collect it and post it to you. Cheaper than their delivery option and I get free brownie points with you

 

Is this the sort of resistor you're looking for? Considering TL;DR I've only read the last couple of posts.

http://m.rapidonline.com/ProductSearch/ProductDetails?ProductCode=62-0169&ModuleCode=519599

[renegadecow]

feedback

My head was spinning for a good couple hpours tracking it down. I paralleled the mag motor with the buckmconverter right through it, but the manual switch I spliced to the positive input of the converter and the negative terminal of the gearbox trigger switch. I kept focusing on having the manual switch hypass the gearbox when on and didn't realize the wiring effectively sends it in reverse. All fixed now by turning the switch into a two way flip switch so it physically cuts gearbox connection when turned on.

 

@Stormin

Thanks, but I've already got the new converters on the way.

[Stormin]

No worries, saves me a trip

[Mike 8-{>]

For future reference you could do this with a small voltage regulator circuit to drop 7.4v down to 3v. A resistor will just get hot and will fail if it isnt high enough wattage.

[Stuey]

That's exactly what he is doing.

[renegadecow]

And the new buck converter which I installed yesterday has died for reasons unknown. I'm absolutely sure there's no feedback malarkey like last time and I only set the output to 4.5V. The device itself is rated to 5A continuous and the Tamiya hyper dash motor only does 2A according to Tamiya. I don't even want to find out how it died (could be a lemon, death by vibration or being turned on/off too many times), I'm just putting in a battery case and manual switch and call it done. To make things worse, the stupid gun won't shoot right after all the trouble of tuning the gearbox. For some reason pressure on the nozzle like being loaded with bbs impedes its movement causing a leak. From 390fps when loaded by gravity it drops to 200fps and below with any mag on. I might be able to modify an AK hop chamber on as anything is better than the "custom" POS it has now, but it's consumed so much of my time already that I'm calling it quits. The owner will likely just keep it for display as it's gone through many gunsmiths before me (all failed) and just use his MG42 for skirmishing with.