#swift flyer

[aaron-the-dork]

So my inktober starts with a boring drawing of a common swift (it's a irl bird species that is considered the fastest flying bird (hawks and eagles aren't the fastest birds in flying but the fastest divers in air)) and stars (that are based on the pokemon move swift that is usually just flying stars)

[lykle]

Quick sketch of the way I think the bodywork around the front suspension must be shaped. The trouble is that the top and the bottom part of the nose must be able to move independently of each other. So I need to leave quite a large gap between them.

It ain't pretty yet, but it is getting there. At least now I have a better understanding of the movement and the shapes involved. I think this part of the Flyer will have to wait till I have time to do some serious modelling, in 3d or in clay.

I think I will leave the front bodywork for now and accept that I will need to come back at it. So, what should I do next? Chassis, control mechanism, steering? Choices choices....

[lykle]

The trouble is..

that it just does not look good.

The current suspension layout will work, technically. But not aesthetically. It just looks cluncky.

OK, I know, it is only a initial design. Now that I have the technical bits working, theoretically, I can start with the "look good" aspect of it. But the basic structure of the construction does not allow for much freedom. For one thing, there is a lot of movement going on and I want to cover it with bodywork. The bodywork will have to be very large or full of big holes to allow for all the movement. I think the solution will be full of holes, like the Blackjack Zero.

Yes, I love a challenge, sure, but there are limits! I will start sketching again and hopefully my next post will be a sketch of how I made it look good. I think I will need to modify the technical solution a little to maximise the looks.

I have been designing a lot of stuff lately, from a nice toy for a big boy (a stainless steel trebuchet) to a lovely candle holder in wood and aluminium. I am in the process of making the candle holders now. So all these creative juices must now be channeled into finding a good looking front end.

But, this is what keeps me alive and kicking. So, so far so good.

[lykle]

I knew it was tough..

but I hoped it would not be this hard. Shortening the Swift Flyer has become a real issue and the only way I have been able to come close to the 3 meter target is by switching powerplant.

By using a Suzuki Burgman (for instance) I can get closer to the 3 meter target. Yes I am sitting a lot higher that I intended to do and I will need to figure out how to insulate my bum from the heat of the engine, but it is somewhat realistic I think.

Power is a bit more limited, but I did not want a super fast machine anyway, it is much more about the fun than the outright speed.

[lykle]

This is getting real...

.. tough now. This is where the final overall layout is to be defined.

I have the structure, the general positioning of the parts and how it can work. Only trouble is, it is more than 4 meters long at the moment. That is not very realistic.

So I will need to try and shave a meter off, somehow. This is not going to be easy. OK, 3 meters is the target length and to be honest, I don't think I will be able to get to that, but I need to get a lot closer to it than 4 meters.

There are three areas where I think I can reduce the length a bit. One, I can make the whole front suspension set up smaller and shorter, that will help a little. Two, I can change the sitting position and size, plus move it further forward. But I have the check to make sure the brake and throttle pedals are OK. Three, I can see if I can modify the bike frame in such a way that I can move the whole thing forward. But I don't want to cook my back with the exhaust pipes.

Nevertheless, I will need to shorten the design. I think I will gain most in the seating area. The trouble is, I like sitting low and deep inside a vehicle. Reminds me of my racing days. The only way I can make up a lot of space is by sitting more upright and higher off the ground. Pity. I will do some measurements on my car and see how I sit in there and what the total length requirement is. That should help.

Alternatively, I could redo the front suspension again. Flip it around, make it point forward instead of back. But that means I can only use one swing-arm per side, not two as I have now. The cross-member would fit under my knees, across the Flyer. Springs, shocks and tilting mechanism must all be fitted under there.

It will be a nightmare in packaging, but that's what we got brains for.

[lykle]

This is a quick render how it could look, using the twin pivot points. The shocks would mount as close to the centre of the lower pivot point as possible, as to minimise their effect on tilt.

I think the upper swing arm is going to be a long arm that is connected to the crossmember via a bearing. So the cross member will not rotate, it is just there for stiffness.

I have not yet put any thought in the chassis holding the pivot points, the blue piping. So don't look too closely at that.

[lykle]

Back to ...

.. the suspension. It is killing me! The range of motions is so much more than in a normal cars suspension.

But I am beginning to see the light of day, I think. I now have a tentative solution. It still is too complicated for me, but I think it is the only way I can do what I want to do and still have good road holding.

Basically, I need to mount the top and bottom swing arms on pivots, with the pivots fixed to the chassis. A hydraulic cylinder will tilt the chassis and that will move the top swivel point as well. This will cause the wheels to tilt.

So far so good. Now all I need to do is put the shocks and springs on it and I am done. But, where to mount the shocks? I settled on the top swing arm, with the fixed end mounted on the bottom swivel plate. I want to minimize the impact the springs have on the tilting motion. I don't want a bump at one wheel to change the tilt angle.

To be honest, I am having a little trouble visualizing the kinematics here. I think I will start to make a small scale model, just to understand the range of motions better and to see what the springs will do to the tilt forces. I think I have enough scrap metal to build a decent scale model.

Nevertheless, the construction is a lot more complex than desired, but it is as simple as I can make it. So all I have to do now, is test to see if it will work, and then simplify. Simple!

The final thing I still need to look at is the steering control. I want front wheels that I can steer. I could use the free to caster idea, but I want to be able to control the wheel angle, especially at very low speeds. The route of getting the movement from the steering wheel to the wheels is very convoluted. So I thought using push/pull cables, but there is too much play in them. My latest idea is to use hydraulics. Un-powered, just displacement. Like a lot of outboards on a speedboat are steered. Again, I need to do some experimenting as I have no idea what effect hysteresis will have and how the force feedback will be.

So, in closing, for once it is not back to the drawing board, it is to the workshop. For the first time.   

[lykle]

All this thinking about control methods etc made me realise that I need to keep track of a lot of information, options, reasonings and decisions.

So I dumped everything into the mindmap I had started and it is becoming quite a mindmap. Multiple pages and a lot of detail. Maybe I should have used a requirements tool like RequisitePro or something. But the mindmap makes it easy for me to zoom in and pick at a detail until it works.

Here is just one page. OK, I admit, it is the busiest page I have at the moment but that is because it is the subject I am working on at the moment. I am dreading the moment I start on the legal and rules part of the map!

Anyway, back to thinking again...