Be careful going down hill

[shrewsbury11]

Well I took the plunge and ordered my Sofrider. It arrived 27th August and myself and a friend built it in about 2hrs or so.
First impressions when we tried to ride it were not good neither of us could get going and my friend is a very accomplished cyclist.
So we moved the seat back and second time around managed to get going. Very wobbly but we managed and every time we had a go started to get easier.
For the last 3 days I have been cycling a 4 mile course down some very quiet lanes with some fairly steep hills. Managed hill starts ok, but difficult starting off from junctions especially if there is a tight right turn to make, have to line yourself up to have more of a straight start.
Not as wobbly found that as long as you were putting a bit of power on while pedalling it kept you straight but if you changed down because you were coming up to a junction ready for an easier start away you tend to lose control.
So today thought I would try my luck at a steep hill nearby that I will be using when I start to commute.
It’s about a mile long with some quiet steep gradients, it was hard work but managed it ok.
So turned around to cycle home don’t know if I thought I’m getting the hang of this so let’s try going a little faster downhill but these things have a tendency to bite you back.
Lost control big time once you get a wobbly on very difficult to control. Braked but my backend started to overtake me. Lucky no traffic coming the other way got dumped on the road nettle stings on one leg and graces on the other.
But worst of all bent the big cog on the bottom bracket. Don’t know if you can straighten them but I expect will have to buy a new one.
Had to phone my wife to come and pick me up.
Not put me off, just put me back awhile.
So these videos on you tube that say Cruzbikes are easy to ride ignore them they are not. You have to learn to ride all over again. It’s a completely different style. But great fun.
Andy

 

[Shakey]

Hi Andy,
I suspect you tried to go too fast too soon. There is a definite learning curve to these bikes. I found that when learning there is a tendency to become unstable during the transition from coasting to peddling & surprisingly from peddling to coasting as well.
You can go fast .... but I really wouldn't recommend it for the first few hundred kilometres.
Maybe try practising interval peddling & coasting in a quiet level place.
cheers
Richard

 

[shrewsbury11]

Hi Richard

Thanks for your reply. Yes agree it unstable going from peddling to coasting and visa versa.
Will try out the interval training and will be taking it steady going down hill in the future.
Hope to be back on it by the weekend.

Andy

 

[KenM]

So long as the teeth on the front cog are OK I've found that its possible to straighten them - sort of. I haven't managed to get mine totally straight but it works fine.
Take it easy on the learning curve! At 9 months I can still notice that I can cut smoother curves at speed downhill than I was doing at 6 months and when I remember what I was doing at 3 months, well that was embarrassing!

 

[John Tolhurst]

Safest way and highly recommended is to maintain pedaling all the way down, just lightly, as the learned ability to keep balance expresses itself through this familiar action.

You don't have to go fast to practice coasting. Most important is that control is not really coming through the arms, strange as that may seem. Rather, it comes from your head, for those tiny fine adjustments. Or from your knee - when I coast hands free, I can steer by moving whichever knee is higher. I move it left or right a few centimeters to balance the bike and move my head side to side to gently arc the steering. With my son on the back, I used to go hands free down our short street, coasting, and let him move side to side to steer the bike. If he headed us to the side of the road or towards a parked car, I'd just grab the bars and take control back again. That was fun!!

If you try to wrestle control at speed you are likely to completely obscure the natural feel of the bike and how it wants to go straight after all, due to the the wheel contact patch trailing behind the steering axis line. (Trail, in steering geometry parlance.)

Safest way and highly recommended is to maintain pedaling all the way down, just lightly, as the learned ability to keep balance expresses itself through this familiar action. Let me copy that as a coda at the front of this post.

 

[Tarmac Terrorist]

Safest way and highly recommended is to maintain pedaling all th

Yes, powered descents are the way to go, if I stop pedaling it wobbles and the only way to regain control is to power on. I have enjoyed some adrenalin pumping powered descents that plastered a smile on my face for the rest of the day.

 

[Robert Holler]

I have found on my Quest the

I have found on my Quest the same thing - keep the power on and it is easier to stay straight. Of course at some point you spin out and have to coast. When that happens I agree with John - a lot is in your head and small adjustments make a big difference. Trying to muscle it/mash it doesn't help.

Of course the same applies to all my previous recumbent high racers too.

The best though - laying the power down in a corner. No heel strike possibility means roll on the power at all times!

Robert

 

[John Dorlon]

I have found that when

I have found that when coasting at high speeds, if I want to transition from coasting to pedaling, it is best to start pedaling slowly - so the first turn or two of the pedals, you are not powering the bike...then you can gently work back into powering the bike by gradually speeding up your pedaling (or maybe the bike is slowing up the next hill).

Put more briefly - it is an abrupt change in non-bike-powering pedaling which causes instability. So just work gently through that transition and it will help a lot.

 

[Charles.Plager]

I have found that when

I have found that when coasting at high speeds, if I want to transition from coasting to pedaling, it is best to start pedaling slowly - so the first turn or two of the pedals, you are not powering the bike...then you can gently work back into powering the bike by gradually speeding up your pedaling (or maybe the bike is slowing up the next hill).

Put more briefly - it is an abrupt change in non-bike-powering pedaling which causes instability. So just work gently through that transition and it will help a lot.

My experience is consistent with this as well. Just start up slowly and go from there.

 

[billyk]

Charles - You're a physicist, right?

Charles - You're a physicist, right?

I have also experienced the tendency of my Quest to high-speed wobble, fortunately without further incident. I've also noticed that this can be triggered by the transition between coasting and pedaling, in either direction. Why is this?

I wonder if it is because the mass of bike+rider on a Cruzbike is so much closer to the axis of rotation of the steering column than on a DF bike. The rider is almost wrapped around the steering column and the heavy parts of the bike itself are in the front. Thus there is less moment (of inertia around the steering column) on an MBB bike than on a DF bike.

When a wobble is initiated on a DF bike, its large moment tends to stabilize it because the main mass remains mostly un-wobbled: it is well behind and far from the axis of wobble. A small correction will suffice. But on an MBB bike, the wobble moves a much larger fraction of the mass and requires a larger correction. Since humans are not so good at such corrections (tend to overcorrect and also tend to lag behind the appropriate correction), an MBB wobble is more likely to grow.

We need a physicist to explain this ...

BK

 

[Charles.Plager]

Hi Billy,
I think there are a

Hi Billy,

I think there are a few different effects that are contributing here.

1) Sitting upright on a DF is more stable than sitting reclined on a 'recumbent. (Just like sitting up on a DF is more stable than being in a tuck on a diamond frame). This is true of all recumbents compared to DF bikes.

2) On SWB bikes, your center of mass is much closer to the steering axis. This makes the bike feel more twitchy. Also, when you start pedalling, you are suddenly changing your mass distribution with respect to the steering axis.

3) MBB bikes do have the steering coupled to the feet. When not used to this, this is a big problem. (This is why I recommend that newbies remove their feet from the pedals when they feel like things are going badly.) If the rider doesn't relax his legs when this starts, I can very easily see this growing into a big problem quickly. I don't know how much of a residual problem this is for experienced riders (although I'm very willing to believe that even experienced MBB riders who aren't used to descending can easily make matters worse for themselves here).

These are what I (currently) believe are the big issues affecting this. (Maybe next time, you guys need to find a better physicist. ).

Cheers,
Charles

 

[John Dorlon]

My non-physicist opinion on

My non-physicist opinion on the why the coasting to pedaling transition is tricky is this:

When you are pedaling but the energy of the pedal force isn't going into the spinning of the wheel, the momentum of your feet and legs spinning has to go somewhere - and it goes into the unbalancing of the front wheel and thus the bike.

I think I could have said that better but hopefully that's good enough to get the idea across.

 

[Charles.Plager]

When you are pedaling but the

When you are pedaling but the energy of the pedal force isn't going into the spinning of the wheel, the momentum of your feet and legs spinning has to go somewhere - and it goes into the unbalancing of the front wheel and thus the bike.

I'm not sure I completely buy that (for whatever that's worth). If you start spinning wildly but are in a gear where you are propelling forward, I think you'll find that your still wobbly.

I think your body just needs a bit to get used to balancing again.

Here's a weird data point: When I ride with my daughter on the trail-a-bike, I find it harder to balance when she is pedaling and I am not than when she and I are both pedaling.