I can’t tell you how many times I have built something that needed a rewire, only to finish building it and the mag runs backwards! Usually because so many manufacturers use the “wrong” colour wires to the terminals, or same colours.
The speed bump is worth investigating. Take the spring out, and cycle it using a screwdriver to turn the gears, depending on when the speed bump happens may help you narrow down what it is. Often the tappet plate can cause it, or the piston picking up a bit odd, and sometimes the sector gear cam (tappet plate post) can be rubbing on the side of the gearbox.
You have to be close to an awesome performing and reliable blaster at this point, ironing out issues and attention to detail you have given it is extraordinary.
Possibly a good thing the mag terminals were backwards otherwise I wouldn’t have found this speed bump in the cycle, just the bottom half with no motor.
That is odd. Process of elimination required. Remove the sector or bevel and try. Just need to eliminate one variable at a time in these scenarios.
Also worth noting when you screw the box together, start with the counter sunk screws first as the locate the sides best. I’ve always done the bottom, the rear most then the front on the LDX boxes.
You must have mentioned that when I bought this second LDX as that’s the process I’ve been following
Found that the sector and spur had the speed bump. Narrowed it down further to just the spur, which is weird because I went through this earlier in excruciating detail. With a 0.1mm shim on either end of the spur gear I’m finding that there is still resistance, I’m assuming that when I first did the shimming I must not have screwed down the gearbox tight enough. (or I didn’t follow the screw tightening sequence)
So with a 0.1mm shim on each end I’ve run out of room in the gearbox to shim correctly. Plan is to buy some 9mm bushings and try those.
Good thing I bought that handy dandy bushing installer/remover a while back. Certainly makes life easy, because nothing else here is
Given you have bearings you could try it with no shim on the top side of the spur. The seating area is the same as a shim, and the centre race touching it should spin freely with the gear.
Well it’s working 27 RPS with a few misfeeds, feels like the magazine is struggling to keep up.
240 FPS but I think that’s just because of a slight t piece/ gearbox alignment issue after using a different pistol grip, when the pistol grip is screwed in tightly it causes the gearbox pins to not line up.
Bit of work with the 9" grinder to take some material off the pistol grip and it should be right
Sorted the alignment issue with some sanding to the pistol grip, looks like hell but it works.
Found it still had feeding issues, then the gearbox locked up
Opened up and removed 0.1 from the spur and increased the gap between the spur and the sector and that appears to have done the trick. Think the learning from this is how consistently I tighten up the gearbox each time.
Back together, few more feeding issues, turns out the LDT t piece that came with this new gearbox shell is too narrow for the LDT style nozzle I’m using, so swapped back to the LDT t piece that I got with the last ruined gearbox which could facilitate the considerable girth of this nozzle.
Still not feeding right so took a magazine apart and completely removed the nubbin a la @Maiphut style to solve that problem.
Big step in the right direction at last
Now weirdly, I’m getting a higher FPS with the 11.1 battery than the 7.4 battery. I might need assistance to understand that weirdness
7.4v battery, average around 290 with a 23cm barrel
Usually if FPS is higher in 7.4v than 11.1v it is a timing issue. Two methods to solve it, can try one or both. Both can be done without upsetting your lower end on the LDX boxes too.
Use a stronger return spring, or shorten the return spring by two loops.
That will help it get to seal quicker before the piston is released.
Trim the tappet plate tail. Start by removing 2-3mm off the lower edge of the wing.
Disclaimer is if you remove to move you wont feed anymore so best to be done in 1-2mm increments.
That will release the tappet plate earlier to give it more time to seal before piston is released.
I would start with the return spring. Then move to the tappet. LDX tappets can normally get close to 30rps without much of a trim and a strong/short enough return spring.
I did recently get some more bits including VERY strong return springs, but I have to test them out as there is a point where the spring is too strong, don’t want to be responsible from breaking peoples tappet plates!
Turns out the spare return spring was about the same strength as the one on this box already. Took one loop out for now and took a bees dick off the fin.
Gotten another 10-15 fps but I feel like there’s still a little room for improvement.
Still has a feeding issue depending on how the magazine is seated, usually end up with some gels mooshed up around the tpiece and forend. Might be an alignment issue between the tpiece and magazine.
Anyway it’s game day tomorrow so I’ll give it a run and see how it goes.
Very much appreciate everyone’s input to get me this far
This whole build has been like a feature length movie…,
…and I’m loving it despite your frustrations!
We’ve all been there many times mate, but that’s the whole point in the learning curve of this hobby. If everything just slapped together and worked perfectly, we’d soon get bored and move onto something more challenging!
Kudos for sticking with it, and now I’m actually back in civilization from out bush, I will endeavour to dig through my inventory and post some pics of the very old skool Silver edge Alloy split gearboxes I have stashed away here somewhere still brand new in their boxes.
Haha yeah that’s exactly how it feels at the moment, just one plot twist after another.
You’re not wrong though, if it all just went together first go it wouldn’t be half as satisfying in the end. Definitely learning a few things the hard way on this one.
Appreciate it mate, keen to see those old school silver edge setups too — sounds like a bit of gold sitting in the stash
Happy to report I made it through an hour of gameplay today with no gearbox issues. Still some magazine feeding weirdness to sort, which I think is nubbin/feed tube alignment related.
I was also getting this error from the MOSFET that I couldn’t work out, and the troubleshooting in the MOSFET manual is vague to say the least.
This would happen intermittently with three different types of mags and both 7.4V and 11.1V batteries.
That is a mystery. TBH I haven’t had issues with mine yet so experience is limited for error codes on them.
Is it on semi or auto when it does it?
It could be the sector sensor is dirty, or not quite detecting the sector (will affect both semi and auto)
The other possibility is the selector switch is just being activated/deactivated between modes when it is fired (occurs if there is movement on the selector plate).
Haven’t been able to get the selector switch and plate to play nice with this gearbox yet (busy solving other issues ) so for now the selector plate is taped in place stuck on full auto. Maybe the tape has come loose.
Need to take another loop off the tappet plate spring too.
27 RPS with a few misfeeds, feels like the magazine is struggling to keep up.
