GX390/420 EggMonster. Full Power Test

Well, a mixed result today.....

Sam and I ventured onto the quarry again for a full throttle test of the EggMonster. Sam tried to capture the rpm reading on video but it was difficult. He did however take a visual reading which he said peaked at 3580rpm. I was hoping for +3800rpm.

We then had a go with the bathroom scales test and we topped out at 48kg thrust, again very disappointing :o( On this last run I suddenly experienced a high frequency vibration occur which was making my face judder????

Upon inspection we immediately noticed that the exhaust bracket had failed and the silencer box was resting against the digital tacho. On the first section of video though it does appear that the bracket could have failed then as it does appear to 'bounce' more than I'd have thought the bracket would have allowed it to??? So if the exhaust wasn't the cause of the last run vibration then we'll have to investigate further. Sam is going to get some thicker steel for a new bracket and we are also going to rubber mount it too.

As for the power/thrust???

I in-putted the Konig prop data into a thrust calculator (calibrated as best as possible) and it showed roughly 47kg thrust @ 3580rpm (pretty much in line with our scales test) and 'only' 14.5hp to achieve it. This is strange as the stock engine is suppose to produce 15hp @ 3600rpm and it has the addition of better breathing, re-jet (although the plug was a little sooty again), billet alloy flywheel and an extensive amount of head milling to increase compression.

Ideally the prop could do with having a little less pitch (15.75" but I would prefer around 14") but it's non-adjustable and so we may have to try the fan assembly and see if we get better results there.

So then........

Were our test too flawed?
Is the engine giving more than 14.5hp?
Are we achieving over 50kg thrust?

"All these questions and more will be answered in next week's show" ;o)

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[weirwolfarroo]

Just a thought on the vibration- we made the outer rim on the cage sectional and loose so it could "Shuffle" - that seems to have killed the vibration.

[lookupparagliding]

@weirwolfarroo Hello Tom, Thank you for info but I think we'll 'suffer' the vibration. Apparently 'gx390atos' has spent ages trying to tame the vibration on his GX390 trike and only got so far. Much more from the 390/420 than from a 200 unfortunately. Paul Bailey told me yesterday that he is developing a 500cc SSDR power-plant and says he's forced to go for a twin instead of a single-pot because of vibration issues. I think it's something I'll have to live with, the frame seems tough enough :o)

[weirwolfarroo]

It didn't look too heavy... was it comfortable?

[lookupparagliding]

@weirwolfarroo Hiya, not mega comfortable really but the harness is a bit too small for me. It's a large and an XL would be better. It was making me hunch over a little. I'm sure I could facilitate a launch.

Cheers,

Rob