Good the hear Swampy

Er...what exactly do you mean by 'in sinc'? Do you mean getting them to provide the same thrust as each other up through the rev-range so that the aircraft won’t yaw? Your donks would be far enough apart to be able to ‘rudder’ the plane just by subtle thrust variations between the two Turbines, yah?

I had a bit of a mixed-bag weekend - I didn't get to fire up the twin 3000's as I was a bit short on the proper fuel hose. So I used that rubbery silicon 'glow' type tube and had a bit of trouble getting some ends to seal properly. I managed to trash a fuel-pump in the process by giving it a tad too much juice (my fault - I didn't read the max volts for the pump correctly). So I spent this arvo having a go at repairing it, seeing as it was stuffed anyways.

After I took the blue anodised pump off the front of the unit, I noticed that the motor ran fine (this time on some AA's as Smithy suggested instead of the LiPo). So the problem was in the pump mechanism itself. I found that the non-driven toothed wheel was frozen solid - probably nipped-up due to over-revving. I managed to work it slowly loose using the end of a plastic peg (so as not to damage anything further) and some oil. I managed to get it moving slightly, but it was still rather tight. So I put the drive-wheel back into the unit, oiled everything up good an proper, and carefully inserted a small blade screwdriver into the drive-pin notch in the drive wheel, and used my cordless drill to spin it seeing it was still too tight for the fuel-pump motor to budge it. That worked out ok, and I sucked the non-driven cog out with one of those 'pick bolts up' magnet thingies.

I could see a small burr inside the blind hole where the non-driven cog's shaft goes, so I got some Tamiya polishing paste (the one you can polish scale model canopies with - super fine), and put a bit of that in the 'bearing' hole. Grabbed one of those round tapered tooth-picks and snapped it off so the end was just smaller than the hole, and stuck the toothpick in the drill and gave it a good spin to lap the bur out. Seems to have done the job, as the non-driven cog now spins freely when it's back in the pump body. Oiled it all up and put it back together - no go. I could feel the motor trying to spin, but the pump cogs refused to turn. So I played around with backing off the two 2mm Allen key screws that hold the pump to the motor body and I got it to free-up nicely. I noticed that by tightening/loosing the two screws in different orders that the revs of the motor went up and down, so clearly there's some alignment thing going on when you torque the screws up and down. Those tiny cogs inside the pump probably have a fairly critical working tolerance between spinning freely, and not spinning at all.

Still, I managed to get it going again and let it run via a recycling bottle of Kero for a few minutes - adjusting the two screws until the unit didn't leak past the sealing o-ring but where the revs didn't die down too much. There must be some sort of knack to getting it just right (??). I'm ordering a new one as a replacement anyways, and keep this one as a 'spare'.

That's about my lot for now - hope to be able to at least fire them up together some time this coming weekend. Should be awesome

You must be itchin to get that A-10 up in the air…

BJ