12 mm 6061: Strong Enough tb Pedal Spindle?

Per :
https://www.youtube.com/watch?v=lD6OQhCeXqs

Jeez, they can't be serious.

It actually works.

Frank's observation about it the "gear" being too low is, IMHO, right on
the money... but it does work - in fact it's the saving grace for the
thing I sail which is basically too much of a pig to paddle - yet the
Mirage Drive means I can get a little bit of leg motion instead of
sitting on my butt for hours at a time.

When paddlers go up against Mirage Drive users in any sort of endurance
contest, the paddlers always win.

OTOH, in a "Tractor Pull" situation, the Mirage Drive rules.
https://www.youtube.com/watch?v=D0rvFdLdplA

Dunno what the physics are, but that's how it plays out.

The thing is an absolute beast going into the wind. Last year I was
stranded on a remote beach with 30-35 mph winds blowing straight onshore
so that I could not paddle out far enough to deploy the sail/centerboard
and sail home: the wind would blow me back on the beach before I could
do anything.

Pulled the Mirage Drive out of the hull storage, inserted it, and no
problem getting offshore enough to deploy everything and sail home.
--
Pete Cresswell

Per Frank Krygowski:
6061 T6 is way weaker than any stainless steel I know about. In
general, going to a solid cross section doesn't add much strength
compared with a hollow cross section of same outside dimensions. Just
based on that, I'm not optimistic about your proposed change.

So: Can you give us dimensions, and an explanation of how the thing
works? Where did the original break? Do you have photos?

Based on what you said, I am going to go at it another way using the SS
spindles that came with the pedals on the broken/warranted cranks (they
only supply entire assemblies because of the way they attach the
pedals).

Took awhile for it to dawn on me... but I think I can make the SS
spindles work without having to cut threads in them like on a bicycle
pedal.

Here's a pic of the two failed cranks showing the pedal ends:
http://tinyurl.com/ycjzoa75

The other end, which pivots on the Mirage Drive, is torn up even worse
on one but had not yet failed on the other: http://tinyurl.com/y7nhz6f9

I am trying to find a video that shows how the components work together,
but have not found anything yet.

Suffice to say that the user pushes the pedals and a system of cams,
cables, and chains flaps the fins back-and-forth under the hull.

I'm no engineer, but the whole thing looks undependable to me -
confirmed by my having broken one cable and two levers to date.... and I
am 76 years old, hardly able to walk... so it's not like I'm some kind
of animal overloading otherwise-adequate devices.

A guy in china is working up a functional equivalent that looks to me
like it might be miles ahead of the Hobie product in terms of
reliability:
https://www.youtube.com/watch?v=gvx-MpCpkPw
https://www.youtube.com/watch?v=qmfoBQPPJo8
https://www.youtube.com/watch?v=fSZbXEbvAF0


--
Pete Cresswell

On Tue, 13 Jun 2017 19:45:17 +0700, John B.
wrote:

On Mon, 12 Jun 2017 13:06:32 -0400, "(PeteCresswell)"
wrote:

Not for a bike, but for a Hobie Mirage Drive as in
http://tinyurl.com/yb3uppbm

I keep breaking Hobie's hollow crank arms and have made some
replacements out of solid 6061.

Was going to tap them for 1/2" bicycle pedals, but now I am thinking of
using the Hobie pedals, whose attraction is that they have no bearings
to rust in salt water - just a spindle through the plastic pedal.

Hobie uses SS for their spindles, but after reading up on threading SS,
I think the path of least resistance would be to get some 6061 in the
same diameter (12mm) and use that instead.

Bottom Line: would 6061 have enough strength? ... This is more of a
recumbent-type config - i.e. the user is not standing/stomping on the
pedals.

6061 isn't a complete description. You need to include the "T" number
as 6061 can have a yield strength of from 14 to 35 ksi, a typical
hardness from Brinell 30 to 95 and a sheer strength of from 12 - 30
ksi, depending heat treatment.

Relative to steel aluminum is a relatively soft metal and I would
guess not be the material of choice for long wearing pedal spindles.

On the other hand a stainless and aluminum mix can cause some
astonishing commission in salt water but there are quite a selection
of barrier "stuff" to electrically isolate the two. I even used a
silicon sealant mix and a year later the parts came apart easily. I
don't recommend silicone sealant as an all purpose solution but it
does, I believe, show that the problem isn't rocket science.


Goodness! The spelling checker blinked. Change the "commission" above
to "Corrosion". :-(
--
Cheers,

John B.

On Tue, 13 Jun 2017 06:52:09 -0700 (PDT), wrote:

On Tuesday, June 13, 2017 at 5:45:22 AM UTC-7, John B. wrote:
On Mon, 12 Jun 2017 13:06:32 -0400, "(PeteCresswell)"
wrote:

Not for a bike, but for a Hobie Mirage Drive as in
http://tinyurl.com/yb3uppbm

I keep breaking Hobie's hollow crank arms and have made some
replacements out of solid 6061.

Was going to tap them for 1/2" bicycle pedals, but now I am thinking of
using the Hobie pedals, whose attraction is that they have no bearings
to rust in salt water - just a spindle through the plastic pedal.

Hobie uses SS for their spindles, but after reading up on threading SS,
I think the path of least resistance would be to get some 6061 in the
same diameter (12mm) and use that instead.

Bottom Line: would 6061 have enough strength? ... This is more of a
recumbent-type config - i.e. the user is not standing/stomping on the
pedals.

6061 isn't a complete description. You need to include the "T" number
as 6061 can have a yield strength of from 14 to 35 ksi, a typical
hardness from Brinell 30 to 95 and a sheer strength of from 12 - 30
ksi, depending heat treatment.

Relative to steel aluminum is a relatively soft metal and I would
guess not be the material of choice for long wearing pedal spindles.

On the other hand a stainless and aluminum mix can cause some
astonishing commission in salt water but there are quite a selection
of barrier "stuff" to electrically isolate the two. I even used a
silicon sealant mix and a year later the parts came apart easily. I
don't recommend silicone sealant as an all purpose solution but it
does, I believe, show that the problem isn't rocket science.

That was some good information John. Too bad this site doesn't allow you to edit your spelling so that you could correct your spelling of "corrosion" since some of the people won't be able to figure it out.

I sort of fail to see how a flipper mechanism like that could require or absorb much power.

Yes, I've already begged forgiveness and corrected the error in
another post :-(

--
Cheers,

John B.

On Tue, 13 Jun 2017 07:30:02 -0700 (PDT), jbeattie
wrote:

On Monday, June 12, 2017 at 6:59:19 PM UTC-7, Frank Krygowski wrote:
On 6/12/2017 4:51 PM, AMuzi wrote:
On 6/12/2017 3:20 PM, Frank Krygowski wrote:
On 6/12/2017 1:06 PM, (PeteCresswell) wrote:
Not for a bike, but for a Hobie Mirage Drive as in
http://tinyurl.com/yb3uppbm

I keep breaking Hobie's hollow crank arms and have made some
replacements out of solid 6061.

Was going to tap them for 1/2" bicycle pedals, but now I
am thinking of
using the Hobie pedals, whose attraction is that they have
no bearings
to rust in salt water - just a spindle through the plastic
pedal.

Hobie uses SS for their spindles, but after reading up on
threading SS,
I think the path of least resistance would be to get some
6061 in the
same diameter (12mm) and use that instead.

Bottom Line: would 6061 have enough strength? ... This is
more of a
recumbent-type config - i.e. the user is not
standing/stomping on the
pedals.

We'll need a lot more information. I did one test ride in a
Hobie Mirage Drive, but I don't remember many details about
the mechanism, and the one photo you linked isn't helping
much. But I didn't think I was able to apply very much
force to the pedals. ISTR wanting a higher "gear," so to
speak.

6061 T6 is way weaker than any stainless steel I know
about. In general, going to a solid cross section doesn't
add much strength compared with a hollow cross section of
same outside dimensions. Just based on that, I'm not
optimistic about your proposed change.

So: Can you give us dimensions, and an explanation of how
the thing works? Where did the original break? Do you have
photos? And in the photo at the site you linked, what's the
grey handle thing that seems linked to a transverse pin?

(And I wonder if there's a kayak discussion group that might
be more appropriate.)


https://www.youtube.com/watch?v=lD6OQhCeXqs

I'm familiar with that. As I said, I test rode one. It was fast, and
kind of fun to generate a serious wake.

But if we're going to do new pedal arms, I'd like to know how they
attach to the rest of the mechanism, and exactly which part broke, etc.

When it snaps, at least its soft enough to drill a pilot hole for the Easy-out.

Speaking of . . . my Roubaix has these removable removable rear fender eyelets that screw into a female boss at the end of the seat stay. The eyelet has a threaded 4mm shank and is made of aluminum. Well, I broke a rear eyelet yesterday and was looking at it in the garage last night thinking, "oh boy, I get to drill a tiny hole in a 4mm bolt stub" . . . The good part is that the metal was so soft and useless that I could grind a slot using a low speed drill and then screw it out. I had previously broken a front eyelet much higher up and bought a set of four SS replacements, so at least I had the part. I didn't like the idea of having to buy a part that should have been sold in the first place.

-- Jay Beattie.

Based on what I've read here and seen locally, real men don't have
fenders. As a substitute they have a black, muddy stripe on the back
of their jersey :-)
--
Cheers,

John B.

On 6/13/2017 8:12 PM, (PeteCresswell) wrote:
Per Frank Krygowski:
6061 T6 is way weaker than any stainless steel I know about. In
general, going to a solid cross section doesn't add much strength
compared with a hollow cross section of same outside dimensions. Just
based on that, I'm not optimistic about your proposed change.

So: Can you give us dimensions, and an explanation of how the thing
works? Where did the original break? Do you have photos?

Based on what you said, I am going to go at it another way using the SS
spindles that came with the pedals on the broken/warranted cranks (they
only supply entire assemblies because of the way they attach the
pedals).

Took awhile for it to dawn on me... but I think I can make the SS
spindles work without having to cut threads in them like on a bicycle
pedal.

Here's a pic of the two failed cranks showing the pedal ends:
http://tinyurl.com/ycjzoa75

Yow! Looks to me like the design wasn't even close to strong enough.
The hole would be astoundingly close to the edge even if it were a solid
bar. For a solid bar, I'd keep the edge of the hole at least 1.5
diameters away from the end of the bar, unless I were really trying to
shave weight. Even then, I'd leave a full diameter.

The other end, which pivots on the Mirage Drive, is torn up even worse
on one but had not yet failed on the other: http://tinyurl.com/y7nhz6f9

I'm wondering how much extra room there is for a bigger cross section,
but that depends on how it attaches to what at the drive end. If the
warranty replacement is identical, I think I'd go shopping for stainless
steel bars. And what the heck, go for solid bars. SS tends to be
expensive, but maybe Ebay or a salvage store could turn something up.

Or again, post to a kayaking group. As flimsy as those bars look,
someone else must have had this problem.

I am trying to find a video that shows how the components work together,
but have not found anything yet.

Suffice to say that the user pushes the pedals and a system of cams,
cables, and chains flaps the fins back-and-forth under the hull.

I'm no engineer, but the whole thing looks undependable to me -
confirmed by my having broken one cable and two levers to date.... and I
am 76 years old, hardly able to walk... so it's not like I'm some kind
of animal overloading otherwise-adequate devices.

A guy in china is working up a functional equivalent that looks to me
like it might be miles ahead of the Hobie product in terms of
reliability:
https://www.youtube.com/watch?v=gvx-MpCpkPw

Thing is, those bevel gears are probably VERY expensive. I'm betting
that's why Hobie went to its cheaper mechanism.

--
- Frank Krygowski

Per Frank Krygowski:
Or again, post to a kayaking group. As flimsy as those bars look,
someone else must have had this problem.

The experts on the Hobie fora claim that, since a rash of substandard
material some years ago, failures have been few or non-existent (can't
recall which).

But, based on a lifetime of experience, whenever I hear "Well, nobody
else is having a problem so you must be the only one...." bells ring and
red lights start blinking for me.... -)
--
Pete Cresswell

Per John B.:
On the other hand a stainless and aluminum mix can cause some
astonishing commission in salt water but there are quite a selection
of barrier "stuff" to electrically isolate the two. I even used a
silicon sealant mix and a year later the parts came apart easily. I
don't recommend silicone sealant as an all purpose solution but it
does, I believe, show that the problem isn't rocket science.


Goodness! The spelling checker blinked. Change the "commission" above
to "Corrosion". :-(

----------------------------------------
CANDIDATE FOR A PULLET SURPRISE

I have a spelling checker.
It came with my PC.
It plane lee marks four my revue
Miss steaks aye can knot sea.
Eye ran this poem threw it,
Your sure reel glad two no.
Its vary polished inn it's weigh.
My checker tolled me sew.

A checker is a bless sing,
It freeze yew lodes of thyme.
It helps me right awl stiles two reed,
And aides me when aye rime.
Each frays come posed up on my screen
Eye trussed too bee a joule.
The checker pours o'er every word
To cheque sum spelling rule.
Bee fore a veiling checkers
Hour spelling mite decline,

And if we're lacks oar have a laps,
We wood bee maid too wine.
Butt now bee cause my spelling
Is checked with such grate flare,
Their are know faults with in my cite,
Of nun eye am a wear.
Now spelling does knot phase me,
It does knot bring a tier.

My pay purrs awl due glad den
With wrapped words fare as hear.
To rite with care is quite a feet
Of witch won should bee proud,
And wee mussed dew the best wee can,
Sew flaws are knot aloud.

Sow ewe can sea why aye dew prays
Such soft wear four pea seas,
And why eye brake in two averse
Buy righting want too pleas.

Jerry Zar, 29 June 1992
Jerrold H. Zar
Graduate School
Northern Illinois University
Title suggested by Pamela Brown.
Based on opening lines suggested by Mark Eckman.
----------------------------------------
--
Pete Cresswell

On Wed, 14 Jun 2017 09:15:55 -0400, "(PeteCresswell)"
wrote:

Per Frank Krygowski:
Or again, post to a kayaking group. As flimsy as those bars look,
someone else must have had this problem.

The experts on the Hobie fora claim that, since a rash of substandard
material some years ago, failures have been few or non-existent (can't
recall which).

But, based on a lifetime of experience, whenever I hear "Well, nobody
else is having a problem so you must be the only one...." bells ring and
red lights start blinking for me.... -)

Well :-) we've got a bicyclist right here on this group that reports
strange and exotic things that happen only to him :-)

But the photos you posted showing what appeared to be square tubing
used as crank arms did appear to be pretty shoddy stuff. Replacing
them with either solid or thicker wall tubes would probably solve your
problems.
--
Cheers,

John B.