Cycling Forums - View Single Post - Pedal car (Dino, Berg,Kettler) questions.

01-03-2007, 09:17 PM

In article <1167879051.563049.112750@i80g2000cwc.googlegroups .com>,
betatron@gmail.com says...
> I'm envisioning some sort of horror created from several gas-pipe
> Huffys. I want at to have at least 2 drive wheels,

That's relatively easy if you have the extra wheel behind the regular
drive wheel, although it will affect steering.

> maybe 3 or 4.

That's getting complicated, given your apparent reluctance to do A-Team
engineering.

> I'm thinking 20" tires or smaller.

I don't think wheels under 20" will work well - you'd need a wide tyre
with low pressure to maintain a good contact area, and if the wheel
doesn't slip there would be problems with the tyre shifting on the rim
at high torque.

> I would probably significantly ballast
> the contraption, likely with snow, improve drive wheel traction.
> In
> general, i'm not fond of a single front wheel solution. I would prefer
> a two-wheel front end which will give a better mount for the plow.

I'd agree with both of those points.
>
> I'd be interested in any pointers anyone might have to a torque
> _increasing_ derailleur lashup. I'm intending to build something that
> will have significantly more torque multiplication than your average
> MTB granny gear. If i understand the concept correctly, i'm thinking
> of being able to shift down to on the order of 4 gear inches or so.
>
> Such a thing seems pretty simple on paper, but ... i don't know
> anything, really.
>
Say you have a 24 tooth chainring driving a 24 tooth sprocket on a 20
inch wheel - that's 20 gear inches. You could get it down to 5 inches
with two sets of reduction gears each with a 48 tooth and a 24 tooth
sprocket, so that's basically two extra bottom brackets and chainsets
that you need to attach somewhere between the pedals and the hub. You
could achieve the same reduction using a couple of 14-28 freewheels
instead so you'd only need to weld on brackets to hold a couple of hubs,
but the stress on the drive train components will be close to doubled
because of the smaller dimensions. I'm doubtful that a regular wheel is
going to handle the torque anyway - I still reckon it would be better to
use the final drive and rear wheel of a small motorcycle, maybe even the
gearbox too.

01-03-2007, 09:17 PM	#54 (permalink)
Rob Morley Guest Posts: n/a	Re: Moving on (Was Re: Pedal car (Dino, Berg,Kettler) questions) In article <1167879051.563049.112750@i80g2000cwc.googlegroups .com>, betatron@gmail.com says... > I'm envisioning some sort of horror created from several gas-pipe > Huffys. I want at to have at least 2 drive wheels, That's relatively easy if you have the extra wheel behind the regular drive wheel, although it will affect steering. > maybe 3 or 4. That's getting complicated, given your apparent reluctance to do A-Team engineering. > I'm thinking 20" tires or smaller. I don't think wheels under 20" will work well - you'd need a wide tyre with low pressure to maintain a good contact area, and if the wheel doesn't slip there would be problems with the tyre shifting on the rim at high torque. > I would probably significantly ballast > the contraption, likely with snow, improve drive wheel traction. > In > general, i'm not fond of a single front wheel solution. I would prefer > a two-wheel front end which will give a better mount for the plow. I'd agree with both of those points. > > I'd be interested in any pointers anyone might have to a torque > _increasing_ derailleur lashup. I'm intending to build something that > will have significantly more torque multiplication than your average > MTB granny gear. If i understand the concept correctly, i'm thinking > of being able to shift down to on the order of 4 gear inches or so. > > Such a thing seems pretty simple on paper, but ... i don't know > anything, really. > Say you have a 24 tooth chainring driving a 24 tooth sprocket on a 20 inch wheel - that's 20 gear inches. You could get it down to 5 inches with two sets of reduction gears each with a 48 tooth and a 24 tooth sprocket, so that's basically two extra bottom brackets and chainsets that you need to attach somewhere between the pedals and the hub. You could achieve the same reduction using a couple of 14-28 freewheels instead so you'd only need to weld on brackets to hold a couple of hubs, but the stress on the drive train components will be close to doubled because of the smaller dimensions. I'm doubtful that a regular wheel is going to handle the torque anyway - I still reckon it would be better to use the final drive and rear wheel of a small motorcycle, maybe even the gearbox too.