Australian Streamliner Bike Build

[Jon]

Not got a heap of real work done on my bike lately, been distracted by a couple of other little projects.

Woody and I are killing email electrons again working on the yaw of my bike again after the Christmas/New Year break.
One cool thing to come from a recent software upgrade (I think) at the smart end  is the ability to show virtual oil streaks on a pressure map (my input is generally limited to a very rough sketch and a cryptic message for the next run).





There is a lot of air crossing the top of the bike and staying attached nicely because of the profile, trying to upset that a bit with a "roofrail" from the canopy back is one of the next two runs.
This at first look will increase roll from the 6 degree crosswind and have little effect on yaw, but........
What i am hoping to achieve is to make it harder for air to cross the bike and upset the crossing air to increase the pressure delta between the two sides of the tail by reducing the pressure recovery on the leeward side and increasing the pressure recovery on the windward side.
Hopefully then we'll start to see some correction from the tail.

The tail extension is off again for now as there is such a small pressure delta that it isnt doing a lot for it's size, if we can increase the pressure delta it may come back, I'm trying one change at a time on the base model rather than just keeping adding changes so that the effects of one change can be easily seen.

Another cool thing is this pressure chart for the midline down both sides;


And from that a pressure delta graph;


This confirms that nearly all the yaw input is at the front of ther bike and very little correction from the rear, because of this I'm trying trying to reduce its input rather than counteract it at the back where there is a very low pressure delta. That is the next run, the base profile is staying the same, front tyre is going to get a bit breezy.

A really handy tool for non educumacated people like me would be a "pressure delta map" that showed the differences of pressure between the two sides as a coloured rendering, , wouldn't it Woody?...

It's probably obvious by now that I am fixated on pressure deltas across the bike, IMHO that is all that is important in a crosswind situation, a high pressure on both sides has no sideways effect, likewise for a symetrical low pressure pattern.
A pressure difference will try to shift that portion of the bike sideways from high to low pressure, the bigger the difference the bigger the push.
The closer to vertical that the two oposing points are the greater the sideways action for the same pressure differential, the only surfaces that have no sideways action  from a pressure differential are a horizontal surface or a vertical surface that runs straight straight across the bike.
There is very few of these, a thin line along the top and bottom of the shell and the bottom of the wheel fairings are horizontal, the front and back of the internal wheeltubs and a thin line up the back of the tail are vertical across the bike.

I'ts never going to be "stable" but neither am I, a little less unstable would be nice though.


cheers
jon  

P.S.  Woody is patient as well as knowing his stuff, nothing worse than a customer with an "opinion"....

[Dr Goggles]

This is going to be one very fast bike, and it's already been an interesting story.

Is there a chance you might be able to knock up a little yellow dog image that can be added to the CFD images...they seem lost without him......

[Jon]

Thanks James, hopefully my bike and I can live up to the expectations I'm setting one-day....

Richard and Janet have taken young Spot away for the weekend.
I've been misjudging them some.
I didn't think they liked bikes much but when we got Dave's bike fired up the other evening it was only running on 3 so we thought if we gave it a bit of a blip it may clear its throat.
When we did that a few times they came out on their front verandah and were waving at us, it's good to have the support of your neighbours isn't it?

I'll put a pic of Dave's exhaust on his build diary.

cheers
jon

[salt27]

This is going to be one very fast bike, and it's already been an interesting story.

Is there a chance you might be able to knock up a little yellow dog image that can be added to the CFD images...they seem lost without him......

Knock up a little yellow dog?
No time for that now, you need to get things ready to roll.
Take care of the dog when you get back.

[Jon]

He has a bit of a thing for yellow at the moment.

[wobblywalrus]

Jon, your tail is thin and small and there are pronounced concave areas where it joins in the fuselage.  It might be ineffective 'cause it is in the aerodynamic shadow of the body.  Note how the tails are on salmon and trout.  The taper of the main body goes almost to the rear of the fin. 

 

[Jon]

Thanks Bo, the tail has pretty good pressure recovery in a straight line, problem is both sides still have good pressure recovery in yaw.

Run 6, 6 degrees yaw, poking along a bit: left side is Leeward side, right side is Windward side, the right side is flopped to make it easier to compare.

The back section of the tail on both sides is above atmospheric pressure but very similar side to side from the wheel back so very little yaw correction, no pressure difference = no side thrust.

I "think" that this is caused mainly by the air crossing the top in a happy state because of the body profile,  I'm hoping the roofrail will stop some of it and at annoy the stuff that does cross to cause a bit more pressure differential.

This picture also shows where nearly all the yaw input is coming from, around the front wheel area, the back 1/2 of the bike from the line above "left side" & "right side" is that close to being the same other than the very top at the rear that not much is happening.

It is interesting to see a very small area of higher pressure air bleeding from right to left where the tail tapers up, visible as a small darker section on "left side", that combined with the top view with oil streaks a couple post back lead to the roofrail idea.

In the future list of runs if the next two don't show promise is a twin tail to get out into free stream air a little better.

Trying one thing at a time in order of preference based on what i think may work, what will stand up to the bike assuming its natural position better and the ease of doing it (plus it needs to look "right" to me)

Again a disclaimer, this is all bulldozer driver aero from my end, it's only what I think I see.
Woody may choose to give some real input.

Cheers
jon

[WOODY@DDLLC]

Jon, you're doing fine! You can drive my aero dozer any time! 

Analysis is a process of discovery not an event. The visibility gets us thinking about things in new ways! 

I can't even stir my coffee now without doing an analysis first! 

[tauruck]

Hey Jon, a few pages back you mentioned a tig tan. There is a smell that goes with it if done right. I got some strange looks at the supermarket while I was buying a few Cokes. Last question,  have you done some mig while wearing sandals?. This is a great thread. Thanks man.

[JimL]

I used to stick weld in a pair of old sneakers....until one day, while I was welding up my horse corrals, I was feeling pain and smelling smoke.  I flipped up my hood, and looked down to find BOTH shoes on fire.  At that moment, I found a great confusion......trying to decide which foot to stomp out first!

That was the day I went and bought the heavy leather boots.  If you find you cant decide, it is time to do something different!

[Dr Goggles]

I learnt to weld when I was about 11 I think. Not long after that I learned that slag is hot. I dropped a ball down the inside of my sandshoe...all I can really remember was how much my dad laughed , I ripped my shoe off so fast it hit the roof of the shed and there was a smell of BBQ...still got that scar on my foot. Lying on the floor under a car is my favorite when a slag ball rolls up against you and you can't move, I have a very neat circular burn on my arm right now from that....then there is the ear burner...... I currently have nicely tanned inner arms all the way to my armpit.....mig tan....The worst one I've had was when working for a friend making some inserts for a fish control baffle(?long story) and I was welding mesh, crack, crack, crack.....thousands of them, no auto helmet, probably did half of them with my eyes closed....burned my eyelids, that was more than a little uncomfortable. Yep, I've done it all..pants, shoes,shirt..car, about the only thing I haven't set on fire is my hair.
If you need a hand on workshop safety I'm not your man.......

[DavieB]

There is a whole process happening outbin the world that I hadn't even imagined:
Someone thinks " I'll make an electric stirring coffe cup", thinks its a good enough idea that they are able to convince someone to fund making and marketing them, then someone buys them........ I do lead a sheltered life.

Thanks Tauruck, there is a distinct smell to a good MIG/TIG/Stick tan.
No sandals here, they must be a popular Sith Ifrican thing, I worked with a couple guys from South Africa and Zim, I could always tell when it was getting cold, they wore socks with them. Double pluggers do leave a nice line though, wouldn't be as nice as sandal patterns though.

One of the handiest things I learnt from an old neighbor is that full cream milk is good for welding flash eye pain.


Cheers
jon

[Jon]

Hmmmm

 Dave seems to left the computer logged on in his name, I probably should have deleted that and reported it in my name.

[rgn]

One of the handiest things I learnt from an old neighbor is that full cream milk is good for welding flash eye pain.

I can't imagine catching a cow while blinded would be easy...

Good to see two generations (yourself and Davie) involved in, and enjoying racing together.

[Captthundarr]

Dr. Goggs, you need to work on the hair aflame thing to catch up with the rest of us and you haven't lived until you've had a small slag ball dance around in your ear!!