"Fat Boy" 12/118 thrust engine

[racket]

Hi Aaron

LOL.....yep its a bit of a beast, the video's sound doesn't do it justice, even when the volume is turned up to full its less than a real idle noise level .

It'll be an interesting ride with 200+ HP , just gotta get my finger out and do the construction

Cheers
John

[azwood]

Aug 5, 2020 21:07:08 GMT -5 racket said:

Hi Aaron

LOL.....yep its a bit of a beast, the video's sound doesn't do it justice, even when the volume is turned up to full its less than a real idle noise level .

It'll be an interesting ride with 200+ HP , just gotta get my finger out and do the construction

Cheers
John

Yeah 200hp is impressive

[azwood]

If my bike makes 100hp I'm happy.btw how to I calculate its top speed is it just roll diameter of the wheel vs final reduction

[azwood]

The back wheels 630 tall

[racket]

Hi Aaron

Your terminal speed is dependant on your drag ( wind resistance) plus a tad of rolling resistance being balanced by your "thrust" produced between tyre and road, drag will vary depending on "frontal area" and drag coefficient which will vary with "streamlining" or lack there of.

100HP should allow ~200-220 kph , my turbine bike developed 115 RWHP on the dyno and even though the bike's drag was horrible with all 1.9 metres of me sitting upright and flapping in the breeze and bits sticking out everywhere on the bike it easily achieved 200 kph in 400 metres with gearing for ~225 kph

Initially I used the standard 41tooth rear wheel sprocket with a 14 tooth on the gearbox output and a 4.813:1 gear ratio inside giving an overall 14.095 :1 ratio but this meant a "theoretical" top speed of near 300 kph with the freepower at 100% rpm , a speed far in excess of the available HP , this gearing limited top speed as it was a super overdrive ratio .

I then made up a huge 54 tooth rear sprocket which produced a 18.56:1 ratio and a potential ~225 kph , a much better match for the available HP and drag configuration.

The rear tyre had an ~82" circumference , so ~26.1" dia , or 663 mm dia, at 82" - 6.8333 ft circumference it required , 5280/6.8333 = 772.68 wheel revolutions per mile , 772.68 by 2 miles per minute (120 mph) = 1545 RPM , multiply by my 18.56 overall ratio meant the freepower was doing ~28,682 RPM at 120 mph ~200 kph , the freepower was good for 33,290 rpm , so 33,290/28682 = 1.1606.. by ~200 kph = ~232 kph.

The complications arise when we don't know the HP and the drag coefficient as well as the optimum freepower rpm , all we can do is make some assumptions , .................in your case your freepower won't be rpm limited as with my Allison wheel, as it would normally have much higher rpm in its original turbo use , but I doubt you'll ever see more than 40,000 rpm for the freepower due to the limited gas energy going into it.

As a rough guess you'll probably need an overall ratio of at least 20 : 1 between freepower wheel and rear wheel to maximise acceleration and top speed

Hope this helps

Cheers
John

[azwood]

Ok thanks John just wanted a starting place to shoot for

[slittlewing]

Great work John, looking forward to seeing the bike come together when you decide on the chassis etc!! All your work in fettling the clearances and flow path amounts will pay off when you are riding it at full power 😈😈

What is the reason for the fairing tube over the turbine nut/hub on your nozzle?
For peak performance in avoiding a turbulent/dead zone of air behind the hub?

Cheers

Scott

[racket]

Hi Scott

Yep , the tube prevents some turbulence, but it also helps mount the straightening vanes so that the actual jet nozzle size more accurately indicates the actual "axial" flow area rather than a possible turbulent swirling mass trying to get out the "back hole" , whether it gives more power , maybe yes , maybe no ..............but at least I gave it every chance :-)

Cheers
John

[racket]

Hi Guys

Finally got around to weighing the combined assembly of gas producer, freepower/trans and oil tank mounted on its framework and it came in at ~135 lbs - 62 Kgs , now have it sitting on a trolley with casters underneath so that it can be easily moved around the workshop, it looks kinda small sitting near the floor.

Currently tidying up and making workspace for the next stage of the process, still not 100% sure what thats going to be, lotsa pros and cons with constraints from where I live and whats available , and most importantly what I'm physically able to do now that my wornout back is getting worse, more painkillers needed :-)

Cheers
John

[jetjeff]

Hi John,

I've "tweaked" my back twice and know how painful it can be. Hang in there, surgery an option?

Regards

Jeff

[racket]

Hi Jeff

Unfortunately the old back is simply worn out , the Physio has given me exercises to strengthen it but they don't seem to help , I'll be 73 in a few weeks , I guess lifes past pleasures are just catching up with me ,its been slowly getting worse over the last decade ........ I've had a good run, no regrets, nothin' in my "bucket list" to do ;-)

The good part is I can still sit at the keyboard and help guys with their builds and get my enjoyment that way.

Cheers
John

[turboron]

John, I will be 80 on September 3. I feel like an old car. Something is always failing or giving up just when you are trying to climb a hill.

Thanks, Ron

[jetjeff]

Hi John/Ron,

I'm 59 and can still windsurf, iceboat and work harder than most millennials (thank God). The opioid crises in the US, has delegated most doctors to prescribe only at end of life situations, although when I threw my back out, I was screaming in pain.

Yes, we can give armchair advise to the new people about what will work, and what won't, the joys of having grey hair.

What's apparent in the manufacturing environment, and in home tinkering with turbines, once we are gone there won't be anybody to replace us.

Regards

Jeff

[racket]

Hi Ron

LOL......that sums it up nicely :-)

Cheers
John

[racket]

Hi Jeff

Yeh we should make the best of it while you can , we never know whats waiting for us "around the corner" , thankfully I got most of the DIY jobs done on the house whilst I was still able to manhandle the equipment around , I can sit back and not have too many jobs stareing at me.

Its been a relatively cold winter here this year , the bones are feeling it , roll on Spring and some warmer weather :-)

Cheers
John