Winfried

Hello,

Someone I know lives in a hilly area where a two-wheel cargo bike rides better than a trike, but even off the bike, she stuggles a bit with balance.

She raised the idea of installing a pair of caster wheels at the bottom of the box, as a way to prevent the bike from falling when the curve's too strong. Effectively, it'd be a cross between a two- and a three-wheeler.

What do you think? Stupid idea? Worth trying?

Thank you.

grumpus

Seems reasonable to me, but I suggest just one wheel - add it on the side she pushes from, so it supports some of the weight when the bike leans towards her. Would be good to have a lever to raise/lower, with some sort of locking mechanism. Careful positioning required so it supports near the centre of gravity or it will just be balancing badly in a different way.

mpetry912 

I would say use two wheels - one on each side - but not touching the ground when riding straight and level

think outriggers or training wheels

/markp

SoSmellyAir

Does she only struggle to maintain her balance while going uphill at slow speeds? If so, wouldn't a cargo e-bike be a safer solution?

Winfried

I forgot to mention it already has a 250W Bafang mid-drive, but it's steep enough that the loaded bike (~150kg/330lbs) only rides slowly, which doesn't help for balance.
I did advise replacing the original Nexus 7 gear hub with a Nexus 8 so as to get lower gear inches, spin more and have a bit more speed when riding uphill.

I also emailed three companies making "training wheels" for adults, to check if they fit a Bakfiets, although at first sight, a pair of caster wheels on the box looks like a better option.

base2 

I'm going to throw my hat in the ring here and vote: "No." It's not a good idea. The bike tilts/leans to keep the apparent center of gravity inline with the line between the wheels. A swivel caster that limits the free coordination between forces interferes with the alignment between actual & apparent centers of gravity will cause a sideways force significantly affecting safe operation. Aircraft have a skid/slip indicator on the dash panel for this exact reason so that the pilot can maintain coordinated flight. This uncompensated sideways force is why tricycles tip, ejecting the rider long before the rider realizes there is a problem.

maddog34

so.. the person thinks adding additional, widely placed, weight will help keep the bike upright when cornering?
nope.

and also consider that once the load transfers to the proposed training wheels, it shifts AWAY from the Front wheel, and Steering Control is no longer happening, as in Front Traction Loss.

conclusion: it's a VERY bad idea.

ps,, training wheels are placed at the REAR of a bike for a good reason.

Bill Kapaun

How much larger cog can you put on back? Smaller ring on front?
If disc brakes, maybe a smaller drive wheel?

Winfried

Thanks for the input. I don't think screwing a pair of caster wheels on the box is a good idea either.

The only option left at this point is a pair of stabilizer wheels on the back… which isn't recommended for a heavy bike say manufacturers. But considering it's the only option left and it's a lesser evil than possibly breaking the box… she'll be the judge.

It can only take drum brakes. Per my suggestion, she already had the useless original IM-45 Roller Brakes replaced with the strongest in the line-up (C6000), which do a good enough job.

She alread had a 40T chairing installed on the Bafang. I'm waiting to learn the tooth number on the cog; Considering it's a Dutch bike and the top three speeds are useless without assist even on the flat, I expect it to be around 19-21T (smallest : 16T; biggest : 23T).

Since Shimano recommends not using a chairing:cog ratio below 2, and considering the much bigger torque from the Bafang, I recommended she had the Nexus 7 wheel replaced with a Nexus 8 with a 20T cog, which would provide gear inches of 26.8"/2.14m on the lowest speed while still respecting the ratio of 2. It would make it a bit faster to climb hills, and thus provide more stability. We'll see.

Winfried

Provided it fits the bottom of a Bakfiets box, this looks like a much safer solution than caster wheels:

Can those parts (tube, wheels axles, etc.) be bought off the shelf, or be found in a hardware store? How do the wheels attach to the tube?

Winfried

Thanks!

squirtdad

The more I think about this more I think this is not a good idea.

It seems that even with a wheel, if you lean over enough to for the wheel to hit it will likely act a fulcrum point and could cause the baksfiet to tit toward it.

It would be worse at speed and when turning

Maybe something spring loaded for the hill the can be pulled up for otherr times? 2 wheels on the road? it still could be a risk on turns

forgive the lack of technical draftsmanship

Winfried

Thanks for the input.

I do worry about the bike falling on its side if one of the stabilizer wheels hits the road, although she's cautious because of her disabilities.

It looks like I might get a free contraption as seen on those second-hand bikes from the Post Office. With luck, it might be retrofitable on a Bakfiets with no engineering skills.

Winfried

CG = center of gravity

So it looks like it's important to find the right length for the axle: Too short, and the bike might tip over; Too long, and the axle might break because of the lever effect (and be a pain to park).

Winfried

A welder might be interested in making a pair of bespoke stabilizers for the Bakfiets, and its ~200kg/440lbs total weight (cyclist + bike + cargo).

What advice would you give for the design + welding?

Kontact

They already make those. Search "adult sized training wheels".

Winfried

Not for such a heavy bike.

"Over 250 LBS"

squirtdad

I have been following the various threads about the OP's situation, and think the real solution (whether it is financially feasible is a different discussion) is to go to a 3 wheel bike


https://www.amsterdam-bicycle.com/sh...-classic-wide/

https://www.bakfiets.nl/en-en/models...narrow/classic

Winfried

In the absolute, yes. But she already bought a two-wheeler and lives in the country, where it'll be hard to resell, and probably not without a serious loss since cargo bikes are still mostly a city thing.

That's why before going that way, I was looking for infos before giving up. It looks there's simply no solution that'll take the weight of a cargo bike.