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Author Topic: APS/Ω Gas turbine bike build  (Read 554503 times)
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bbarn
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« Reply #1065 on: October 06, 2015, 02:27:23 PM »

Consider making the rear of your bike a little less blunt Anders. You will already have a large area of separation drag behind the rider. Adding a big flat rear fender will leave a large pocket of drag in that area, think of it as an anchor hanging off the back.

The illustration I use when describing separation drag is a rowboat vs a canoe. If you imagine a rowboat with a flat rear end and a canoe with a tapered rear then climb into each one. Now give each of them three equal strokes with an oar. Which one will coast farther?

This is because the rowboat has separation drag that is much more prevalent than what you would find on a canoe. There may be other considerations you have there in terms of length, portability, storage... but if not it is free advice use it how you see fit.
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Mobacken Racing
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« Reply #1066 on: October 06, 2015, 02:40:16 PM »

Consider making the rear of your bike a little less blunt Anders. You will already have a large area of separation drag behind the rider. Adding a big flat rear fender will leave a large pocket of drag in that area, think of it as an anchor hanging off the back.

The illustration I use when describing separation drag is a rowboat vs a canoe. If you imagine a rowboat with a flat rear end and a canoe with a tapered rear then climb into each one. Now give each of them three equal strokes with an oar. Which one will coast farther?

This is because the rowboat has separation drag that is much more prevalent than what you would find on a canoe. There may be other considerations you have there in terms of length, portability, storage... but if not it is free advice use it how you see fit.

Hi bbarn!

Thanks for your reply, I am glad that you post ideas and suggestions open for discussion here. As you might have guessed I have very little experience with aerodynamics so I appreciate it.

My idea was to make a Kamm-style tail to keep the overall length as short as possible, and judging from bike fairing pictures I´ve found on the internet the result looks pretty similar to a "real" Kamm tail.

/Anders
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bbarn
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« Reply #1067 on: October 06, 2015, 02:47:47 PM »

I figured you had some ideas there, you seem to think well ahead of the problems. Like I said, it is free advice so if you don't use it no issues, if you do use it...well, you get what you paid for!  wink
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fredvance
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« Reply #1068 on: October 06, 2015, 03:26:05 PM »

Look at the rear of Joe Amo's grey bike, Larry Forstall's "Guppy", Ralph Hudson's bike and Bill Warners bike. I consider these bikes the best of the best. cheers
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Old Scrambler
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« Reply #1069 on: October 06, 2015, 05:14:42 PM »

Another BEST.......

http://wpmedia.driving.ca/2014/01/img_6079.jpg?quality=60&strip=all&w=800&h=520&crop=1

or look up: Tom Mellor Speed Junkie...............
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2018 AMA Record - 750cc M-CG HONDA CB750 sohc - 136.6 mph
2018 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 143.005 mph
2018 AMA Record - 750cc M-CF HONDA CB750 sohc - 139.85 mph
2018 AMA Record - 750cc MPS-CF HONDA CB750 sohc - 144.2025 mph

Chassis Builder / Tuner: Dave Murre
MattGuzzetta
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« Reply #1070 on: October 06, 2015, 07:12:14 PM »

Anders, I love your bike and self made turbine! cheers Your build site is one of my "must check" nearly every day for the past few years. Actually running it and the speeds you have attained is just spectactular.
Your Kamm tail idea is interesting and should be an interesting experiment.  I have used the Kamm tail on 2 vehicles, one a Bonneville 500cc streamliner and the other a 125cc motocycle for the Vetter High Mileage contest some years ago....(about 35 years,  but who is counting?) I will attach some photos of the streamliner model and the car as run at Bonneville and some pics of the bike with and without a rider.  Your idea of having a tank for resting your chest on is something we did as well and it worked wonders for us on our long ride. Having your chest supported by the bike helps you with steering control as you only need your arms to steer the bike, not to hold your body up. 

This picture shows the top view of the streamliner model with the clipped tail.


This picture is the car without the wheel covers and unpainted showing the fiberglass foam monocoque
construction.  We had to supply info to the SCTA throughout the construction to let them see how the
car was built as there was no tube chassis.


This is a pic of the car running at Bonneville, we made 137 MPH with a Triumph 500cc flat track motor
that came out of Gene Romero's bike.  It had about 48 hp so the Kamm type tail didn't hold it back so much.

 
This is the car in line showing the flat tail. I did have the tail open to use the vacuum at the
rear to help draw in air for cooling the motor.....at least that was the theory!


This is the 125cc Suzuki with about 10 hp that we ran cross country.  This also has the Kamm type
tail with the opening for theoretically filling the turbulent air with air coming through the shell.


A better pic of the back tail.


This pic shows how the rider creates much drag as we were not able to get down as we wished. 


The problem with bikes and riders is that the riders body is terrible for aerodynamics and it would be nice to spend a few days in a low speed wind tunnel to see what could be done to help that out.  I would like to see the difference of a Kamm tail compared to a tapered to a point tail as the turbulence from the rider might just screw up the best of streamlining  from the rider back, it would be fun to try!
Just keep the info coming, your experiment is very interesting to many of us out here! grin
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Mobacken Racing
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« Reply #1071 on: October 07, 2015, 04:25:33 AM »

I figured you had some ideas there, you seem to think well ahead of the problems. Like I said, it is free advice so if you don't use it no issues, if you do use it...well, you get what you paid for!  wink

Smiley

Look at the rear of Joe Amo's grey bike, Larry Forstall's "Guppy", Ralph Hudson's bike and Bill Warners bike. I consider these bikes the best of the best. cheers

Another BEST.......

http://wpmedia.driving.ca/2014/01/img_6079.jpg?quality=60&strip=all&w=800&h=520&crop=1

or look up: Tom Mellor Speed Junkie...............

Thanks! I Googled them and they were great looking bikes, lots of inspiration for a future set of aluminum fairings.

I could make some room for experimentation with the tail section with a hole cut in the rear plate and a removable extension that tapers towards a slim ending, then I can try both an open and a closed Kamm tail and a longer and slimmer tail to find out which design that has the lowest drag.
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Mobacken Racing
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« Reply #1072 on: October 07, 2015, 04:46:15 AM »

Hi Matt,

Thank you very much for your praise! It feels like I am on the right track when I reached those speeds with "only" 150hp or so, and I think some further experimentation with the fairings will pay off.

Looking at the GPS log from the runs the speed increases fast up until 240km/h when the curve flattens out quickly and when I pass the one mile marker there is almost no speed increase at all, so the extra power from water injection combined with the (hopefully) lower air resistance should get the bike close to or even beyond 300km/h next summer.

Very nice pictures, I´ll save them in my aerodynamic folder for reference. The 125cc tail looks somewhat similar to the one I´ve built except that my tail isn´t as narrow because of the wide rear wheel.

I suffer from the same problem with getting the head behind the fairings, but I have figured out that if I cut a part of the wind screen away I should be able to bring the top of the helmet down considerably without losing too much line of sight. I´ll have my feancee to take a couple of pictures of the bike with me on it before and after modifying the windscreen to show the difference.

I´ll make sure to investigate this thoroughly and report about my findings here, if I want to get anywhere near the 349km/h class record I really need a set of slippery fairings. Plans are being made for building a new 300hp gas turbine engine for the bike so in 10 years or so I might actually have a bike that can compete with these darn fast electrical motorcycles... smiley
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Mobacken Racing
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« Reply #1073 on: October 07, 2015, 04:27:51 PM »

As I might have mentioned before the helmet hits the wind screen when I try to get down behind it, so I just got back in from an hour in the workshop that I started by marking the section that needed to be trimmed down.



Here I have cut the section away, I had no one to take a picture but I can get the helmet much lower behind the wind screen now so probably a big gain in aero drag. I´ll ask my feancee to take some pics this weekend with me on the bike. smiley



After that I made the last pair of brackets for the water injection tank.



It fits the frame like a glove and stays in place firmly with a pair of nylon zip ties, the height turned out just about right for resting the chest against it while sitting on the bike.



Cheers!
/Anders
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manta22
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« Reply #1074 on: October 07, 2015, 04:36:58 PM »

Anders;

That top photo scares me. If you suffer sudden hard deceleration, that windscreen is going to slice your face like a knife. Can you make the windscreen a little higher? The aero shouldn't suffer since otherwise your helmet is in the airstream and I'd bet it has more drag.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
Mobacken Racing
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« Reply #1075 on: October 07, 2015, 04:54:12 PM »

Hi Neil,

The top photo shows the helmet position before I cut the windscreen, now I can get the helmet further down so the windscreen edge isn´t in line with the visor any more.
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« Reply #1076 on: October 08, 2015, 09:50:16 PM »

Anders, make another Aluminium tail piece and hold it in place with double sided tape.
Shape a new section with foam and cover that with glass.

You can do back to back testing with both tails. cheers
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Mobacken Racing
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« Reply #1077 on: October 09, 2015, 01:59:47 AM »

Anders, make another Aluminium tail piece and hold it in place with double sided tape.
Shape a new section with foam and cover that with glass.

You can do back to back testing with both tails. cheers

I think I will do the extended tail as a learning project in sheet aluminum to get a chance to learn more about it.

I despise glass fiber, a material that cannot be welded cannot be trusted either.
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bbarn
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« Reply #1078 on: October 09, 2015, 08:14:14 AM »

Anders, make another Aluminium tail piece and hold it in place with double sided tape.
Shape a new section with foam and cover that with glass.

You can do back to back testing with both tails. cheers

I think I will do the extended tail as a learning project in sheet aluminum to get a chance to learn more about it.

I despise glass fiber, a material that cannot be welded cannot be trusted either.

Do not fear glass Anders!!!! I too once lived in the dark ages with regard to glass. You can actually weld it with epoxy. It is a very forgiving material to work in. There isn't as much voodoo in it as I had ever heard.

You have the talent and knack to pick it up, I have seen your work. Once you learn how to work with it and become comfortable with it you will embrace its ease of use. Those hard to shape and time consuming pieces become a breeze with glass.

Trust me, I am a complete convert. The stuff is ridiculously strong and resilient too when a proper schedule is used. The new epoxy resins require little if any ventilation and have zero smell. You can layup parts in your living room if you wanted!

With the 3D printer you can make molds too....I promise, try it on something small and you will be disappointed you waited so long to use the stuff.
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Mobacken Racing
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« Reply #1079 on: October 10, 2015, 08:26:08 AM »

Hi bbarn, I hear you about the glass fiber but since I am a metal working guy I think I will stick to sheet metal as far as possible. Smiley

I took the bike outside to take a couple of pictures to see how the riding profile would look like. I can also decide how to further improve the fairings, feel free to make suggestions if you have some bike aerodynamic experience.



This is much better than before, moving the seat and cutting off a segment of the wind screen helped me to get down further behind the fairings. I think moving the foot pegs down and back a couple of centimeters will make the riding position a little less cramped, I´ll look into it.



I will try to measure the frontal area somehow from the pictures, it cannot be overly much judging from the pics.



Cheers!
/Anders
« Last Edit: October 10, 2015, 08:29:05 AM by Mobacken Racing » Logged
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