[python] Re: Python/Hipparion Trike - Questions
- From: "25hz" <25hz@xxxxxxxxxx>
- To: <python@xxxxxxxxxxxxx>
- Date: Thu, 5 Jan 2006 22:11:38 -0500
> > But - what´s about stability when braking hard with a Python/Hippo
> > only by front brake?
>
> Contrary to older expectations, the python does not fold up when
> front braking hard at higher speeds. At least I never noticed this.
> I suppose the trike version to behave similar.
While I was trying to sort out the high speed-downhill issues, I tried a
couple things with front wheel braking too. During hard braking with the
front end, I noticed I could do two separate things. On the flat, I could
use my legs to push on the pedals during hard braking so that I stayed
pushed into the back of the seat, but this seemed to unweight the pivot and
give the python the same kind of "lightness" as fast downhills. Going
downhill and trying the same thing just exaggerated the effect. If,
however, during hard front braking I left my legs out of it and relaxed, and
let myself get slid down and settled into the lower portion of the seat,
then the weight on the pivot was maintained or even increased, and there was
no stability or jack-knifing feeling at all. Hard braking like that on a
downhill wasn't quite as effective because (depending on the steepness of
the hill) the bottom of my seat was either perpendicular to gravity, or even
pointed slightly down, so I ended up with more weight on my pedals than I
wanted because I was sliding forward due to the braking. Still a technique
to practice and perfect :)
> > Another question: where can I get affordable hubs for stub axles?
> > Which standard hub can easily (like the sachs drumbrakes) be modified
> > for 12mm axles?
>
> No idea - maybe you get that from wheelchair suppliers.
Being intially (and still) a trike builder, my friends and I found 4
solutions to finding wheels with "stub end" axles.
1. 20" (406) BMX wheels come with heavy duty 14mm axles. They are more
than strong enough to take being supported on only one side without bending.
To make them truly "stub end" simply loosen the axle nuts and bearing nuts,
shift the axle as far as you can to one side, tighten the bearing nuts back
up, and you're done. Picture of a "stub-end" mount for a trike:
http://bikes.jkcc.com/new%20king%20pin%20on%20wheel.jpg
You can also just buy the hub, but the hubs are usually 48 spoke so you need
to buy a 48 hole rim with them, or use a different spoke count rim and do
some funky spoking. The 14mm BMX wheels complete are only about $45 Cdn and
are super strong, and very durable.
2. A cheaper but slightly less durable option is using the wheels off one
of those 3 wheel stroller/joggers
(http://www.chariotcarriers.com/images_english/index/carrier_thumb.gif).
These aren't as strong as the BMX wheels, but they come in 12, 16 and 20"
versions and usually come with a 1/2" axle and precision bearings. They
also come with either aluminum orsteel rims. These wheels are more than
strong enough unless you are over about 200lbs or a spirited rider, or both.
They are usually in the $40 Cdn range, but the nice thing is they also come
with the stub axle, a tire and a tube. The other option is you can pick up
the whole jogger at a flea market or garage sale.
3. Another option is to buy a hub like the Shimano M475 (about $30 Cdn),
pop the bearings and races out, do a little machining and then press in some
precision bearings. We like these hubs because they have enough meat in the
flange area to have room to machine the bearing race a little deeper and a
little wider for the precision bearings(12 x 28 x 8mm 6001-2RS). You also
need to add a compression tube in between the bearings and the 12mm bearings
I used were about $10 Cdn ea.
http://bikes.jkcc.com/part%20pics/modified%20disk%20hub.jpg
The hubs come in black and silver and 32 or 36 hole. The total cost for
these hubs is about $40 Cdn, and then you have to get the spokes and lace
them into your rim of choice. I've laced them into 451s and 16" rims. Nice
thing, is they will take a disc brake. The only drag, is that you need
access to a lathe or machinist and if you screw up, you lost a hub. Here
are those hubs laced into 16" (305) rims:
http://bikes.jkcc.com/16%20inch%20disc%20wheels.jpg
The black ones are on a tadpole trike I'm finishing, and the silver ones on
the left are going on the python delta conversion.
4. The last option we are using is to buy a 20mm MTB hub, make a couple
20mm to 12mm adapters out of aluminum, and use the same kind of 12mm bolt as
with the M475 hubs. These hubs are about $60 each, but we feel they have a
couple advantages over option #3. They already come with high quality
sealed, precision bearings, they already come with a perfectly fitted
compression tube, they also have disc brakes and they are very strong. The
best thing though, is we don't actually have to machine the hub, we just
take some small aluminum round stock and make a couple adapters that takes
all of about 20 minutes:
http://bikes.jkcc.com/part%20pics/20mm%20to%2012mm%20adpters.jpg
Pardon the blurry shot, but the bolt is a Gr 8.8 12mm, the adapter on the
left has a big hole for the bolt head to sit in, a 12mm through-hole and is
ued on the outside of the wheel. The adapter on the right is simpler in
design, has a 12mm through hole and is used on the inside, or disc side, of
the hub.
The final question, I guess, would be "Why don't you just use wheel chiar or
drum brake hubs??" Well, they're either difficult to find, crazy expensive,
or both. A few of us have metal lathes, or have access to use them, so for
"custom" wheels, we use option 3 and 4. For anyone that wants a simple,
no-machining option, I would recommend option #1, or #2 if you are a lighter
rider.
Sorry about the epic :)
============================================================
This is the Python Mailinglist
//www.freelists.org/list/python
Listmaster: Jürgen Mages jmages@xxxxxx
To unsubscribe send an empty mail to
python-request@xxxxxxxxxxxxx
with 'unsubscribe' in the subject field.
============================================================
Other related posts:
- » [python] Re: Python/Hipparion Trike - Questions
