Rolle aufgrund von Hinterradplatten?

No, ride with a flat tire and brake and loosen the brake and tell us the difference.
Greetings Wolfram
 
@wolfram
I just suggested ride with flat tire and then braking would be the worst thing to do, and suggested you should RELEASE the brake immediately! Especially when the tail is out of track. So why are you suggesting me to try the opposite? Do you think it's safe to do?
 
Then you can feel, if releasing the brake can help.
Try these things isn't safe, but it help's to understand what's going on.
If you would ask me, i think most people would brake, if the tire goes flat, me too.
 
Well I might have breaked before as well. But this is what these discussions and measurements are for?
Now that we discussed this, I would try to avoid braking, and steering out of the straight as well. I also hypothesize that trying to steer back into the straight might help. All of course depends on whether you have place available. If you are heading for a ditch or tree, rolling over might be the safer option after all...

There must be a safe way (not involving personal risk) to test this.
How about testing this on a scale model?
 
I don' know if braking makes it worse or not, do you? But i will test it, and that's the thing.
Greetings Wolfram
 
flowi schrieb:
On a normal bike there is no problem at all if you lock the rear wheel, so it's not that simple
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It is very simple, we are talking about threewheelers that are not leaning into turns. They are stabilized by their rear axle. This is why most velomobiles don't even have a rear brake, it is too dangerous if you loose that stabilisation by accidentally locking up the wheel. Locking up the front wheel(s), on the other hand, is relatively harmless.

Any vehicle that leans like a twowheeler is stabilized by the front axle, if that starts slipping it is really difficult to regain control whereas the rear is easy.
 
In den Filmchen die ich gemacht habe kann man sehen ,wieviel besser die Führung in der Kombination Reifen schmal Felge breit wird.
So wie es aussieht sind min 3mm Unterschied nötig. Das spricht sehr gegen Reifen über 28mm, das scheint auch für die Innenreifen Lösung zu gelten.
Liebe Grüße Wolfram
 
Felix schrieb:
It is very simple, we are talking about threewheelers that are not leaning into turns. They are stabilized by their rear axle. This is why most velomobiles don't even have a rear brake, it is too dangerous if you loose that stabilisation by accidentally locking up the wheel. Locking up the front wheel(s), on the other hand, is relatively harmless.

Any vehicle that leans like a twowheeler is stabilized by the front axle, if that starts slipping it is really difficult to regain control whereas the rear is easy.
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What does it mean, "stabilized by the rear axle". A bicycle is just unstable and needs constant corrections by the driver.
And first you say it's stabilized by the rear, and then you say stabilized by the front.
 
wolfram schrieb:
I don' know if braking makes it worse or not, do you? But i will test it, and that's the thing.
Greetings Wolfram
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Correct, it comes from what I understand of it.
If you are in a corner when this happens, you're probably doomed for a roll anyway. Once the front wheels are away from the line of travel and pulling the front in a new direction, the tail will try to travel in the old direction and thus be pulled out of the corner and you won't be able to counteract that. So my suggestion only applies to when you're driving straight, or maybe very very slight bends where you can steer the front back to the straight-ahead line.

I admire your courage that you want to test this on a real velomobile.
But please be very careful, this is dangerous stuff and you risk rollovers or worse. Make sure you have plenty of space to roll/glide in any direction and wear protective stuff. I would really recommend to test this on scale models first.
 
Nochmals zu den Videos, jeder kann zuhause Luftablassen , eine Gummimatte drunterlegen, oben auf das Velomobil drücken lassen oder besser noch, jemand sitzt drin . Dann mal kräftig hin und herbewegen.
Dann weisst du schon, wie toll
die Geradeausfahrt wird.
Im Video mit 28mm Reifen und 30mm Felge sieht man sehr schön ,wie der Reifen bei stärkerm seitlichem Zug nochmals extra ausweicht, so ensteht wohl ein Impuls den man im Kurveneingang bekommt und der schwierig wieder einzufangen ist.
Liebe Grüße Wolfram
 
flowi schrieb:
I just suggested ride with flat tire and then braking would be the worst thing to do
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Actually, if this happens at high speed braking is the only thing that could possibly slow you down.
It was already said: but it is the natural thing to do.
flowi schrieb:
and suggested you should RELEASE the brake immediately! Especially when the tail is out of track.
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OK. For a short moment this may help. I guess you could see this as an inverted pendulum.

But what about selective braking?
Let's say when your tail veers to the left and you steer to and brake on the left side, this should counteract the movement.
(Of course this would require tank steering or single wheel braking on a tiller)

A very good practice would be a frozen lake like this:

Maybe have spiked wheels in the front (to have good steering and braking) and a "slippery" back wheel in the back.

PS: Fixed some spelling mistakes. Btw: If the brake breaks, this may break up your braking. :rolleyes:
 
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ChristianW schrieb:
Actually, if this happens at high speed braking is the only thing that could possibly slow you down.
It was already said: but it is the natural thing to do.

OK. For a short moment this may help. I guess you could see this as an inverted pendulum.

But what about selective braking?
Let's say when your tail veers to the left and you steer to and brake on the left side, this should counteract the movement.
(Of course this would require tank steering or single wheel braking on a tiller)

A very good practice would be a frozen lake like this:

Maybe have spiked wheels in the front (to have good steering and braking) and a "slippery" back wheel in the back.

PS: Fixed some spelling mistakes. Btw: If the brake breaks, this may break up your braking. :rolleyes:
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Yes it's an inverted pendulum situation.

>Let's say when your tail veers to the left and you steer to and brake on the left side, this should counteract the movement.
But only if the center of mass is still to the right of the left wheel. Because velomobiles are so long and narrow this gives you only a tiny window of opportunity to do this.

So yes, independent left&right braking would theoretically help, if you can handle it properly. Without it you would need to steer carefully to keep it in balance, and at speed I'm not sure if this is humanly possible.

Air drag and rolling resistance will also slow you down. So letting it roll out seems still the safer option

I also thought of a frozen lake for trying but the front wheels still have grip in a real case, but not on a frozen lake. And if the front wheels would have sideways grip, eg by using spikes, you are probably still going to roll over.
 
flowi schrieb:
Air drag and rolling resistance will also slow you down. So letting it roll out seems still the safer option
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Have you ever ridden a velomobile? It takes a looong time to roll out. Not much air drag here.
And if you're going down a hill and don't brake you may even accellerate without braking. Even with a flat and higher rolling resistance.
Just mentioning.
flowi schrieb:
I also thought of a frozen lake for trying but the front wheels still have grip in a real case, but not on a frozen lake. And if the front wheels would have sideways grip, eg by using spikes, you are probably still going to roll over.
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Maybe. Just start slowly. Some spike wheels can be adjusted by the tire pressure.
High pressure gets you less gripp (because the spikes are on the side), lower pressure means more grip.

However, even when rolling over on a frozen I would assume far less damage than on asphalt or a busy road.
 
I made a rough 1:10 scale model of lego to test (rather than driving a real velomobile without rear tire). I tried to get proper sized wheel base and track and estimated center of mass. The driver is replaced by an old lego locomotive that has a chunk of metal on one side (the "body") and a flatter part of metal on the other (the "legs") :) . The total mass I suppose should be (1/10)^3 times a full scale mass, so around 100 grams. I dont have a scale in that range so I hand-compared it with a bottle of 100ml... I roughly checked the center of mass of the model, assuming it's about in the middle between front and rear wheels on a real velomobile.
Of course the scale model goes slower than a real velomobile. How exactly to scale these speeds I'm not yet sure. My current estimate is that the 1:10 model requires about 3.5m/s to match a full sized velo at 11m/s. But the instability in the model behaviour starts much earlier, only with a perfect straight ride this model can do that speed.
The instability mainly comes from the amazing tendency to rotate 180 degrees, even without braking. Only if it drives perfectly straight to start with and does not turn at all, it will stay straight. It looks like when the rear wheel has no traction, the center of mass really wants to be in front of the two front wheels. I think this is because the center of mass (=the driver himself) will travel straight ahead in that case, no matter what the front wheels are doing. And if it has enough speed the model then will roll over when it reached 90 degrees (or earlier maybe I can't tell exactly).
Front wheel braking seems not so sensitive as I imagined. As long as you go straight it does not seem to matter much even if the brakes are equally strong. And going straight seems mostly determined by the steering.
For more definitive results I think this test should be done more accurate, especially the center of mass, total mass, and scaling of the velocity. Also the model should be more robust, instead of shattering to pieces or ejecting the "driver" every time it rolls over :)
 
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