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How2 design ergo handle and stress on the arm/elbow



 
 
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  #1  
Old November 21st 04, 08:27 AM
teachndad
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Default How2 design ergo handle and stress on the arm/elbow


Present wrist and arm problems have caused me to think about designing
an ergo handle for MUni/ trials.

Pardon the following long-winded presentation, I did the best I could to
make my point clear. I am looking for riders to answer with either
technical expertise, and/or knowledge of how the muscles of the forearm
and hand work in concert.

I did a search on handles and found only the stuff on Coker stuff, which
doesn't help me here.

Has anyone tried to build a handle that feels more relaxed to the hand?
I ride most of the time left hand linked to the handle, but at times, I
do use my right hand, but it isn’t my strong side.

If I sit on my MUni and relax my arm and let it meet the handle (Miyata
style), my left wrist is rotated slightly to the left. If I was holding
a metal post in my hand, I guess, that it would be pointing to 2:00
o'clock and slightly upward. Grabbing the Miyata handle, forces the
wrist to rotate to the right and then you have to move the top of the
nuckles almost level(parallel) with the top of the seat handle. This
seems like an unnatural position for the wrist and hand. Why not design
a handle that matches the more natural wrist/hand position – that which
I refer to as the two o’clock position.?

I think the Reeder handle sort of does, this, but from looking at the
images on unicycle.com, it doesn’t point up ward, but more or less
horizontal.

Then there is the GB4 handle for Cokering or 29ing. But from looking
at the pictures at unicycle.com, this handle points away from the rider.
I was looking more for something that might be sort of a Reeder handle
style, but pointed more upward to a more natural position.

So, has anyone built a handle as I have mentioned - that ‘s assuming you
can visualize the configuration from my description?

Now, for the next part, I wonder what stresses would be placed on the
elbow and shoulder when doing MUni or trials compared with using
existing (Miyata style)handle designs. IMHO, while the current Miyata
style handle design places my hand/wrist in an unnatural position, it
does seem to however, create a solid muscle platform from which to
direct the movement of the uni when hopping or gapping. But it does
IMHO present problems for the muscles on the top of the fore arm and
hand.

1 )If a newer more ergo design was used, would the muscle platform be
the same, stronger or weaker and would more stress be placed on the
elbow and maybe even the shoulder with the newer ergo design?

In summary, I am looking for answers to the above question #1 and number
2 (below).

2) Does anyone have a handle like this, knows anyone who can make it,
and can share any experience with it?

I won’t even consider mounting a brake handle on this new style of ergo
handle at this point. Let’s keep that out of the discussion for now.

Thanks,


--
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Rod Wylie

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  #2  
Old November 21st 04, 08:56 AM
john_childs
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Have you seen the handle made by Scot Wallis:
http://www.wallisdesign.com/HANDLEpics.html

It has a nice comfortable shape and a different angle than other
handles. It seems to position the hand in a natural and comfortable
position.


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  #3  
Old November 21st 04, 11:54 AM
GizmoDuck
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Rod,

I've had a few good rides on the GB4 handle, one or two brief rides on a
Reeder, and thousands of kms on a std KH handle. Quite a few kms on the
miyata too (but forget the Miyata- it's almost the worst handle I've
ridden)

My thoughts:
-The KH handle is a solid platform but not a large one to rest your
hands on. I don't think it places your hand in an unnatural position,
but it does hurt after yanking on the handle for a while (but so will
anything). It has a lot of pulling power though.
-The Reeder handle allows your palms to close over the bar (a palmar
grip) and is angled to give a lot of pulling power. I think it is more
comfy than the KH for distances but I don't think it has any more
pulling power than the KH. The Reeder handle actually sits quite high
(ie points upwards) when mounted to a KH seatbase, because of the curve
of the base). I don't think you'd want it pointing much further up or
it will have no power at all when pulling on it- your elbow would be at
too flexed an angle.

-The GB4 handle is a great setup for distances, and lets you cruise at
high speed for long periods because of the position your hands rest in
(kind of like a time trial bar on a bike). You can also put both hands
on the handle, and that takes a bit of pressure off your saddle area.
However, because of the way it is angled (11 and 1 o'clock positions),
it has very little power/leverage. It freaks me out everytime I descend
a steep hill- I ended up on my bottom for the first time ever today when
the unicycle went out from under me. That would not have happened with
a KH handle. The GB4 also has less leverage for off-the saddle power
climbs, but is great for just cruising up a hill. I have modified it
slightly by putting a cut down bar-end on one of the prongs of my GB4
handle- that's helped a bit, giving more hand positions for high
leverage situations.

I don't quite understand the first part of your question- but as far as
I can make out- in terms of hand stresses, the KH/Miyata style handles
uses a hook grip (kind of like holding a suitcase), whereas the GB4 and
Reeder handles utilise a palmar grip (holding a bar). Both of them
utilise the same powerful extrinsic muscles of the forearm. I don't
think the stresses on your hand are any different.

In terms of your forearms, the GB4 handle sit your forearms in a
relatively neutral position, whereas the Reeder/KH/Miyata in a slightly
supinated position (turned anticlockwise- radius and ulnar). I think
for long periods the neutral position is going to be more comfortable,
since you're not using muscles to actively hold the forearm supinated.

The stresses on the shoulder and elbow would depend on how flexed they
are, which is dependent on how low/high the handle is mounted. I don't
think there's too much you can alter with these particular handles
because they attach to the seat (although you can adjust seat angles and
also where you drill the holes in your seatbase for the handles). The
GB4 handle seems to sit quite high though.

Anyway, I'd get the Reeder handle if you want to do MUni; or the GB4 if
you want comfort for long distances, and not too fussed about
leverage.

Hope that's useful,

Ken


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  #4  
Old November 21st 04, 08:39 PM
Tall_Dave
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It's a long time since I worked as a sports trainer, so I'll leave that
all alone, but as a sculptor, I will share my thoughts from a technical
angle.

One way to make a grip that will perfectly fit your hand would be to use
a synthetic polymer*over a 'keyed' metal armature (skeleton).

For example, make an armature in steel/aluminium which projects forward
from the front handle bracket bolts, or the seat post (like a brake
lever). Have grooves/ lumps (like on rebar) for the gloop to bond/key
to.

With gloves on, mix up a batch of muck and form a ball in the palm of
your hand. Squeeze it over the armature and keep still until it sets up
enough for you to let go.

Generally the longer something takes to dry, the stronger it will be.

When it's dry file off the sharp bits and sand it all smoooth.

* Gloop ideas:

auto-body-filler
fibre reinforced epoxy
PC-7
JB Weld
expanding polyurethane foaming resin

-Polyester resin might be a bit brittle

If you wanted to, you could do the maquette in wax/plaster/plasticine
etc and cast multiples for others to use, in gloop as above.

I'm imagining that such an item might have lots of little overhangs etc
which would preclude a rigid mold - you might think about a product from
Corning called "Silastic 3487" for a flexible mold making material. It's
not cheap, but if you were planning on making lots, it would be
economical.

If you're interested, i could sketch out a rough plan for you, and
attach it as an image file.


David


--
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An itinerant Aussie sculptor,
in Columbia SC USA
mailto: TallDaveOS AT yahoo DOT com
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  #5  
Old November 21st 04, 11:13 PM
S_Wallis
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Thanks for the mention, JC.

When I started designing my handles, it was because I felt I would be
able to lift the muni more forcefully with less hand and arm pain if I
had a handle that actually fit my hand and had a way to wrap my thumb
around it. Also I wanted a handle that did not flex so that if I needed
a quick small lift to clear an obstacle I would not have to compensate
for loss of response from the handle flex. After a year of testing my
molded handles I can say that I can pull much harder on climbs and hops,
and I do not have any problems with hand pain. I do get muscle soreness
in my forearm when I do a lot of hard climbing, but it is because I am
able to pull harder without finger pain stopping me, so that's a good
thing.

My “DeathGrip” handles that I will be releasing soon were designed by
going through the hand positioning exercise you describe. First, I
designed and CNC machined a mounting base for the handle, then attached
and shaped modeling clay to make a rough shape while sitting/standing in
the riding position on the unicycle. I then made a rubber mold from
that shape, cast some urethane resin copies, and modified those by
filling and grinding them until I had a shape I liked. I then used that
as a pattern for a more refined mold to make prototypes for testing. I
am on the 3rd revision now and the shape seems to suit almost everyone
who has tried it. Any shape is a compromise because of the wide range
of hand sizes and shapes, and people’s individual biomechanics.

My DG handles slope down to the thumb side, not up as you describe. The
angle you describe does not seem natural or comfortable for me or other
people I have used for input, but that doesn’t mean it wouldn’t be good
for you. You could easily cut and re-weld a Reeder handle to do that.
You might try mounting a stock Reeder with washers under it to test the
angle before actually modifying it.

If you want to sculpt your own shape, the method Tall_Dave outlined will
work. Finding a material that can take being slammed on the rocks
repeatedly is the challenge.


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how to do it." Pablo Picasso
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  #6  
Old November 22nd 04, 07:44 AM
teachndad
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I am familiar with the Wallis DEATH GRIP handle. I saw it at CMW 2004.
I did place my hand on the handle, but for a short time, and forgot to
really try it out on the trail while it was mounted on Scott’s MUni. I
do remember it being VERY comfortable. Unfortunately, as I was
considering this thread, I couldn’t remember how it was angled, so I
figured that someone would clarify this. Fortunately Scott did this in
addition to a concise background of the development of the hand
position.

I wanted to see if there was anything that someone else had made. You
never know what you will find popping up in a thread. The muscle
information was very important to me.

To more clarify the hand position I was referring to, I was looking for
a position that would be created if one formed a fist and then put a
slight bend at the elbow, with knuckles parallel to the body.

I currently run a Bridgeman handle on my MUni that I really have
enjoyed. It is mounted to a CF Miyata base, but it still puts my hand
at an odd angle. Since no one has, at least in the last few years had
problems with tendonitis in the arms, probably tells me that current
handles on the market work well for nearly everyone and that my issues
may be centered on poor technique.

Ken’s muscle info is extremely useful. Scott’s idea about placing
washers under a reader handle may work as an inexpensive and simple
alternative to finding what I think would work for me. For Tall –
Dave, I wasn’t planning on making a run of these. If it came to some
sort of design, it would be a one-off.

Anyone reading this really should grab (no pun intended) one of Scott’s
DEATH GRIP handles when they become available. It’s light and strong
and doesn’t flex.


--
teachndad - aka The Munieer

Rod Wylie

'MountainUnicyclingLA.com' (http://www.mountainunicycling.us)
'Greater Los Angeles Area Trails - Images' (http://tinyurl.com/4otql)
'Greater Los Angeles Area Trails - Descriptions'
(http://tinyurl.com/6h8zn)

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  #7  
Old November 22nd 04, 07:54 AM
jagur
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teachndad wrote:
*Anyone reading this really should grab (no pun intended) one of
Scott’s DEATH GRIP handles when they become available. It’s light and
strong and doesn’t flex. *

totaly! when i offered mine up for sale a couple weeks ago i couldnt
belive it sat there for three days before anyone bought it whats up with
that?

its was even # 007, lucky obie.


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  #8  
Old November 22nd 04, 10:19 AM
maroastedpeanuts
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Hey Scott, i sent you a PM.

-Tom


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