ripp
Veteran Member
I'm sorry, I don't speak english, so I torment you (and myself) with a translation program,Sorry
Joined: January 2013
Posts: 230
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Post by ripp on Oct 5, 2015 15:12:40 GMT -5
Hi Anders, even before the free power turbine can find some horsepower, flow loss to avoid! Ralph
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gidge348
Senior Member
Joined: September 2010
Posts: 426
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Post by gidge348 on Oct 5, 2015 19:59:42 GMT -5
I will close the hole behind the rear wheel and add some skirts from the exhaust pipes and backwards to keep air from the rear wheel, I´ve read that the spokes act as a fan so the less air passing through it the better.
/AndersHi Anders, I think you are on the right track with all this, it really comes down to trial and error. I am sure that anything that gives you a reduction in back pressure will be of benefit to the engine even if it is just reducing EGT. Interesting what you said about the spokes, I think you may be onto something there. When you think about it the spokes at the "top" of the wheel will be traveling at twice the speed of the bike in relation to the air so if you do 300kph on the bike the spokes on the top of the wheel will be doing 600kph. I found this interesting old aero dynamics video on YouTube www.youtube.com/watch?v=ftq8jTQ8ANE If you notice the final results the round bar has 9 times the drag of a streamlined shape and the fine wire is 1/10 the diameter of the air foil still has 1.1 times the drag..... Interesting. May be worth looking at some type of "Moon" Disc or something. Could be some big gains there? Cheers Ian...
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Post by Johansson on Oct 6, 2015 4:41:41 GMT -5
Hi Anders, even before the free power turbine can find some horsepower, flow loss to avoid! Ralph Hi Ralph, That is a very good suggestion, thanks for pointing them out! The reason for the "nozzle" shaped turbine exit was because I couldn´t find a larger diameter V-band flange, for the next engine I will make my own flange in the right diameter. The idea of fitting the inner transition cone closer to the turbine wheel hub is clever, probably lots of turbulence there as it is now. I will also make an effort to design the transition duct cross section area constant from the turbine to the NGV, I didn´t think about that when I made the duct for the JU-01 engine. I will close the hole behind the rear wheel and add some skirts from the exhaust pipes and backwards to keep air from the rear wheel, I´ve read that the spokes act as a fan so the less air passing through it the better.
/AndersHi Anders, I think you are on the right track with all this, it really comes down to trial and error. I am sure that anything that gives you a reduction in back pressure will be of benefit to the engine even if it is just reducing EGT. Interesting what you said about the spokes, I think you may be onto something there. When you think about it the spokes at the "top" of the wheel will be traveling at twice the speed of the bike in relation to the air so if you do 300kph on the bike the spokes on the top of the wheel will be doing 600kph. I found this interesting old aero dynamics video on YouTube www.youtube.com/watch?v=ftq8jTQ8ANE If you notice the final results the round bar has 9 times the drag of a streamlined shape and the fine wire is 1/10 the diameter of the air foil still has 1.1 times the drag..... Interesting. May be worth looking at some type of "Moon" Disc or something. Could be some big gains there? Cheers Ian... Hi Ian, Very fashinating experiment, I could never have guessed that the thin wire could cause so much drag. I am not sure that wheel discs are allowed in the APS class, and I don´t really like the thought of having thin metal discs mounted to the wheels at those speeds. Removing the front disc brakes would probably help but I need all the brakes I have to stop the bike on the short one mile tracks around here, with miles and miles of flat salt lake after the finish line I would hardly need any brakes at all. Last night I finished the exhaust pipes and made a set of skirts for the bike tail, I´ll post them here tonight. The bike looks at least 30mph faster with them on! Cheers! /Anders
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Post by Johansson on Oct 6, 2015 13:38:31 GMT -5
Last night I made the second exhaust pipe and welded them together, the aluminum tape is my poor-man root gas. I seem to have managed to make both pipes the same angle and length, way to go Anders! Then I turned my attention to the aerodynamics, I started making skirts for the rear fairing to enclose the rear wheel. I am aware that I am stumbling in the dark here since I have no way of confirming that it actually works until I race the bike next summer. Here is my high tech sheet bending machine. One side almost finished, one to go. Enclosing the rear wheel will keep air from the spokes that act like a fan at the high speeds they will be spinning and hopefully lower the drag. With the left side made I trimmed down the lower edge until it was 21cm from the ground all around, there are some gaps that needs to be closed and so on but that can be fixed later. It was only 5 hours left until I had to get up for work so I dropped the tools and headed for the bed. Cheers! /Anders
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Post by Johansson on Oct 7, 2015 16:27:11 GMT -5
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. 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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Post by racket on Oct 7, 2015 16:46:18 GMT -5
Hi Anders
The bike is starting to look "comfortable" to ride , the chest rest is a good idea as it gives you a positive position for the body, once hard against it you don't need to worry about whether or not you're tucked right in , you only need to concentrate on getting your head down ...............heh heh , naybe a chin rest required ;-)
The "aero' bits are looking good , you want to slip through the air like a fish through water , I often watch the dolphins in the estuary on my afternoon walks , they can swim against the tide with minimal movement due to their streamlining.
Is there are reason for the "cutoff" flat wall at the back of the bike rear fairing ??
Cheers John
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Post by Johansson on Oct 7, 2015 16:51:12 GMT -5
Hi John, I´ve tried to copy the Kamm-tail style to keep the overall length down while not sacrificing the aerodynamics, with a full length taper on the tail it would be at least half a meter longer and tricky to transport. en.wikipedia.org/wiki/KammbackCheers! /Anders
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Post by Johansson on Oct 10, 2015 8:25:06 GMT -5
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 will try to measure the frontal area somehow from the pictures, it cannot be overly much judging from the pics. Cheers! /Anders
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Post by racket on Oct 10, 2015 16:09:11 GMT -5
Hi Anders
That makes sense with the tail end cutoff the way it is.
Yep, you're tucked in nicely , the only thing I can think of is maybe a Moto GP hump in your leathers behind the helmet to fill in that bit of a "valley".
I'll go for a frontal area of ~5 square feet- 0.5 sq meters minimum to ~8 sq ft- 0.75 sq mtrs max , your drag should be pretty good though :-)
Cheers John
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gidge348
Senior Member
Joined: September 2010
Posts: 426
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Post by gidge348 on Oct 10, 2015 20:23:56 GMT -5
Hi Anders, looking good, the only things that I can see is that if there is anyway to drop the seat and foot pegs to get lower, but I think that may be a lot work for not much benefit. Agree with John, the GP bump would help or maybe a helmet without the sharp rear edge? One thing that we have been working on is the inlet duct There are a lot of weird things that go on around there and that is the first part that sees the air. A bell mouth would definitely make a difference to flow over the rest bike. Also get more air into the engine... cooler.... more power... May want to tape some tufts of wool over the bike and have someone drive along side and get some pictures? as long as they are all parallel that is about as good as can be done, if you find some string pointing up, down or forward may give you some areas to look at. Other that that you could always do this.... Cheers Ian...
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Post by Johansson on Oct 12, 2015 4:25:01 GMT -5
Hi Anders That makes sense with the tail end cutoff the way it is. Yep, you're tucked in nicely , the only thing I can think of is maybe a Moto GP hump in your leathers behind the helmet to fill in that bit of a "valley". I'll go for a frontal area of ~5 square feet- 0.5 sq meters minimum to ~8 sq ft- 0.75 sq mtrs max , your drag should be pretty good though :-) Cheers John I agree that a camel hump on the leathers would improve things, as Ian points out the helmet has a nasty edge on the back that might upset air flow as well. I will see if I can borrow a road racing set and see if it makes any difference before I go and buy new leathers. That frontal area sounds about right, I will see if I can use Photobucket to measure it from the up front picture. Hi Anders, looking good, the only things that I can see is that if there is anyway to drop the seat and foot pegs to get lower, but I think that may be a lot work for not much benefit. Agree with John, the GP bump would help or maybe a helmet without the sharp rear edge? One thing that we have been working on is the inlet duct There are a lot of weird things that go on around there and that is the first part that sees the air. A bell mouth would definitely make a difference to flow over the rest bike. Also get more air into the engine... cooler.... more power... May want to tape some tufts of wool over the bike and have someone drive along side and get some pictures? as long as they are all parallel that is about as good as can be done, if you find some string pointing up, down or forward may give you some areas to look at. Other that that you could always do this.... Cheers Ian... Getting air into the engine without upsetting the aerodynamics is a problem, even more so with the upcoming JU-02 that has roughly twice the mass flow. Looking at the bike I think that lots of air reach the intake through the gap between the front fender and the fairing, the mesh covered "head light" hole is probably not helping much with both the mesh and a crow nest of wires in the way of the air flow. I think that small and thoroughly considered changes between each race is the only way to go, I have nowhere to do any road tests with strings, measuring time rolling from 100km/h to a halt or any other way of low speed aerodynamic testing so I have to do my testing at the races instead. My friends are all just as busy as myself so I can´t expect any help with it either.
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Post by racket on Oct 12, 2015 4:43:43 GMT -5
Hi Anders
LOL...........take the easy way to higher speeds .....fit a bigger engine ;-)
Cheers John
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Post by Johansson on Oct 12, 2015 5:00:50 GMT -5
Hi Anders LOL...........take the easy way to higher speeds .....fit a bigger engine ;-) Cheers John I like the way you are thinking John.
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gidge348
Senior Member
Joined: September 2010
Posts: 426
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Post by gidge348 on Oct 12, 2015 22:14:42 GMT -5
Hmmmmm air is weird stuff ............. www.youtube.com/watch?v=-2dQfEfs_7I ..... check out at 54 seconds in.... I wonder if the flat rear is the way to go or have a tapered or open end, may be something to test next time out. I don't care what the question is the answer is MORE POWER Tim the Tool Man
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Post by Johansson on Oct 13, 2015 5:04:21 GMT -5
That is a neat trick my father showed me when I was young, if you cut grooves in the handle you can get it to start spinning really fast while floating in the air. I have plans to make a removable tail extension so I can try both flat, extended and open rear fairings, I will most likely buy a planishing hammer and learn how to make sheet aluminum parts with it. Should be fun!
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