Gyrobike

[steelpillow]

Staring to brew up a gyrobike, homebuilt in Whiffland ca. 1980. Intended for a historical novel so it needs to be plausible for the period. That means internal combustion, not electric. The autogyro is in fact the lightest form of powered heavier-than-air craft for a given lifting capability, ditto the motorcycle for road travel. To keep the rotor diameter down to no more than the length of a large car, it will have a concentric twin rotor.
I had hoped that, like a hang-glider, it could be steered by weight-shifting. But it looks as if engineering considerations for the engine location may enforce an excessive height and pendulum stability, in which case shifting movements could not be large enough and it would need an articulated rotor.
The three options for engine location are:
1. Between the wheels, as on a bike. Problems include heavy and lossy power train to the pusher prop, as well as the aforementioned pendulum stability.
2. Behind the rider/pilot, as on the typical autogyro. Problems include a high centre of mass on the road and a long gear shift rod leading to sloppiness.
3. Hybrid with the engine behind the driver and the road gearbox between the wheels. Problems include nearly as high a centre of mass, and a heavy power train to the gearbox (there is ample power from the flight engine so road losses are unimportant).
The photo shows a composite layout of a Suzuki RGV 500 racing bike of close-enough vintage with a part-made and damaged Wallis "Little Nellie" Autogyro kit, plus scratchbuilt rotor blades. The Wallis rotor is laid out to show how much higher the bike riding position forces the co-axial rotor. Some other bits (Ford 'Woody' wheels and Wallis aeroshell) are there to prop up the important ones. I took it as a record of my own thoughts but it looks so cool I had to share it.
I hope to bring occasional updates as work progresses.

[PR19_Kit]

Just the white X in the black box I'm afraid, no visible pic.

[Weaver]

That rider is far higher than he needs to be...

I think the solution here is a feet-forwards motorbike with a shaft-drive engine. That way, the rider is nice and low, and your final drive axis is right for the prop, although you'll still need some sort of transmission to get up to the prop (no getting away from that one really). If the FF bike's engine shifts the CofG too far forwards, you could always give it a roof and shift the rotor forward to match: after all, the rotor isn't powered.

Feet-forwards motorbikes:

Malcolm Newell's Quasar:



Royce Creasey's Voyager:



Ecomobile (rear-engined!):



Carver leaning trike:



The Carver has actually been developed into an autogyro called the PAL-V:

(pics: By PAL-V Europe NV - www.PAL-V.com, CC BY-SA 3.0 nl, https://commons.wikimedia.org/w/index.php?curid=38353213)

[Tophe]

Wow, these bikes with rotor are great, will you add your own?

[steelpillow]

Just the white X in the black box I'm afraid, no visible pic.

No idea what is causing that. Four possibilities:
1. The Dropbox server is refusing the standard file request from your browser. This seems unlikely as it works for most other folks.
2. The browser is buggy and is subtly mangling one of; the Dropbox request, the received response with the image in, or the image file itself.
3. Your browser config or settings are blocking the image. Possibly you have cross-site requests disabled or Dropbox blacklisted or something.
4. A firewall in the path is blocking the image, reasons as for 3.
My suggestion is that you try another browser and see if that works. If it does, then you need to figure out why your preferred browser is misbehaving. First step is to google what that white X actually means. It might mean image unavailable or image blocked or image file broken.
Hope this helps.

[Steel Penguin]

weirdly, the 1st photo shows for me in chrome, but not IE, where like Kit, I just get a little white X in a black box
if I try to get the pic in IE it says not available

[Caveman]

Have you seen this guys bike?



https://youtu.be/NNSCGV_x_f0

On your plausibility requirement, co-ax gyrocopters really aren't a thing. Because they need inertia to keep the rotors turning a long rotor is much better than a couple of short ones. Not saying it's not possible but it's a serious compromise for an arbitrary length requirement - but only in the world which we exist in...

[steelpillow]

weirdly, the 1st photo shows for me in chrome, but not IE, where like Kit, I just get a little white X in a black box
if I try to get the pic in IE it says not available

That does suggest it is a browser issue. IE does not handle security issues well. Nowadays, Microsoft are deprecating it in favour of Edge, so maybe it's time for users experiencing problems to move on? If it's on an older version of Windows and Edge is not available, then both Chrome and Firefox make excellent alternatives.

[steelpillow]

In reply to a couple of posts:

I did assume a feet-forward design when I first started. Basically the Wallis stretched a bit, with two proper road wheels and handlebars. But all that stretching and strengthening for road use made it heavy. Thanks somebody for the Molnar image, that illustrates the point nicely. I may still have to go back to it, but the conventional crouching position offers a much more compact and lightweight/robust frame.

A driveshaft adds complexity, cost and above all weight, so a chain is preferable for the road. Conversely, the prop needs too much power for a practicable chain to carry, though I have seen twin-chain solutions on superbikes.
In fact the drive train is pretty complicated. The road wheels need several gears and spin slower than the prop, which needs only one gear and with luck matches the engine revs, eliminating even that. So the prop drive must be taken off before the road gearbox. Both obviously need clutches and a third clutch is needed for a low-powered short-duration spin-up drive to the rotor before takeoff. That spin-up drive should be tapped from the prop drive, as a fail-safe against engaging it when the prop is not running. The road gearbox needs to be close to the engine to avoid inertia delays when the lay shaft (between clutch and gearbox) changes speed and to have a tight gearchange mechanism from the foot pedal. Molnar seems to have added a second, road engine here to solve the drive train problems, much as Whitehead did a hundred and fifteen years ago. But that's yet more weight.

The PAL-V is a two-seater so is inherently a bigger beast. It is also technologically as far ahead of my gyrobike as mine is of Cierva (about four decades in each case). Hence it is able to absorb the weight of a third wheel and lots of movable gizmos. But I am rather amazed that its quoted rotor diameter is much the same as the old Wallis and Bensen single-seaters. That suggests both advanced materials and higher airspeeds. I need to look again at all-up weights and rotor disc loadings.

The inertia argument against the twin-rotor is not necessarily true. Given the same swept area, the twin has 70% diameter. This means that it spins 140% faster for the same tip velocity. Given the same surface loading, the twin also has 70% chord and overall surface area and weight remain the same. Since both mass and velocity (as percent of dia) are the same in total, gearing the two rotors together leaves the net inertia - the integral of mass x velocity over the span - unchanged. This gearing is necessary during spin-up for takeoff, so it might as well remain there throughout flight. The main downside is that the spin-up drive must maintain torque to 140% higher rpm. Keeping the rotor diameter down is far from arbitrary, as it allows use of a standard parking bay and also reduces the structural forces involved when locked fore-aft during road travel.

Oh, and his bum is in the air because it wouldn't stay down without glue he is standing up with the excitement of it all.

[NARSES2]

I can see the pics  and you would need to keep your head down 

Nice stuff

[scooter]

How apropos for this particular thread

[PR19_Kit]

Yes, the first pic shows up in Chrome, but I DETEST the way Chrome handles my favourites.

What the devil is Edge and how come M$ haven't told me about it before now?

[scooter]

What the devil is Edge and how come M$ haven't told me about it before now?

Edge is the new IE

[PR19_Kit]

What the devil is Edge and how come M$ haven't told me about it before now?

Edge is the new IE

Hmm, they publicised that well............................NOT! 

[steelpillow]

Edge is the default browser for Windows 10. If you are using an older version of Windows then IE is still the standard and MS won't bother to tell you more.
Either way, Firefox can replace it and has add-ons such as Classic Theme Restorer if you prefer that kind of interface.