make a softtail into a hardtail?

[Steve Knight]

Anyone know of a bar to replace a shock on my suspension bent? It uses a
standard shock. I find that if I have enough air in it to get rid of the pedal
bounce the rear wheel slams down into all holes very hard. I am about 210 but I
need about 250psi in it to keep the bounce down. If I have about 100 or so PSI
the bounce is gone and no slamming and the lack of the shock is not that big of
a deal.
I don't want to have to spend 300.00 or so for a good shock that would let me
control the problems. So if I could remove the shock and just replace it with a
spacer that would be good. Save some weight too.



--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

 

[[email protected]]

On Tue, 17 May 2005 23:22:11 -0700, Steve Knight
<[email protected]> wrote:

>Anyone know of a bar to replace a shock on my suspension bent? It uses a
>standard shock. I find that if I have enough air in it to get rid of the pedal
>bounce the rear wheel slams down into all holes very hard. I am about 210 but I
>need about 250psi in it to keep the bounce down. If I have about 100 or so PSI
>the bounce is gone and no slamming and the lack of the shock is not that big of
>a deal.
> I don't want to have to spend 300.00 or so for a good shock that would let me
>control the problems. So if I could remove the shock and just replace it with a
>spacer that would be good. Save some weight too.

Dear Steve,

If you haven't already checked, here are two related sites
that offer calculators about recumbent suspension and pedal
kick-back:

http://www.kreuzotter.de/english/efeder.htm

http://www.kreuzotter.de/english/eschwinge.htm

If you stuff your dimensions into these, they might suggest
a suspension solution or at least a length for the bar that
you have in mind.

If you switch to a bar, you may have to find a machine shop
to get something the right length and strength that will
attach to your particular shock mounts.

Carl Fogel

 

[AndyC]

"Steve Knight" <[email protected]> wrote in message
news:[email protected]...
> Anyone know of a bar to replace a shock on my suspension bent? It uses a
> standard shock. I find that if I have enough air in it to get rid of the
> pedal
> bounce the rear wheel slams down into all holes very hard. I am about 210
> but I
> need about 250psi in it to keep the bounce down. If I have about 100 or so
> PSI
> the bounce is gone and no slamming and the lack of the shock is not that
> big of
> a deal.
> I don't want to have to spend 300.00 or so for a good shock that would
> let me
> control the problems. So if I could remove the shock and just replace it
> with a
> spacer that would be good. Save some weight too.
>
>
>
> --
> Knight-Toolworks & Custom Planes
> Custom made wooden planes at reasonable prices
> See http://www.knight-toolworks.com For prices and ordering instructions.

One of these might fit:
http://www.progressivesuspension.com/cvt5.html

They have two stage compression, allowing a stable platform for pedalling
and open up for bigger hits.
There are other versions now too - they're quite common in the MB world.

AndyC

 

[dkd]

On Tue, 17 May 2005 23:22:11 -0700, Steve Knight
<[email protected]> wrote:

>Anyone know of a bar to replace a shock on my suspension bent? It uses a
>standard shock. I find that if I have enough air in it to get rid of the pedal
>bounce the rear wheel slams down into all holes very hard. I am about 210 but I
>need about 250psi in it to keep the bounce down. If I have about 100 or so PSI
>the bounce is gone and no slamming and the lack of the shock is not that big of
>a deal.
> I don't want to have to spend 300.00 or so for a good shock that would let me
>control the problems. So if I could remove the shock and just replace it with a
>spacer that would be good. Save some weight too.


If the thing slams into holes when you pump it up until it doesn't
work any more, what makes you think that replacing it with a metal bar
will change that situation?

The idea behind the shock is to keep from jarring you when you hit
bumps, since you can't climb out of the saddle on a recumbent. Get
rid of the shock absorber and your body will have to absorb all the
shock instead.

If you want to replace the shock with a metal bar, just get a metal
bar about 1/2" thick (or whatever matches your shock) about the length
of the shock and drill two holes in it.

 

[Phil, Squid-in-Training]

dkd wrote:
> On Tue, 17 May 2005 23:22:11 -0700, Steve Knight
> <[email protected]> wrote:
>
>> Anyone know of a bar to replace a shock on my suspension bent? It
>> uses a standard shock. I find that if I have enough air in it to get
>> rid of the pedal bounce the rear wheel slams down into all holes
>> very hard. I am about 210 but I need about 250psi in it to keep the
>> bounce down. If I have about 100 or so PSI the bounce is gone and no
>> slamming and the lack of the shock is not that big of a deal.
>> I don't want to have to spend 300.00 or so for a good shock that
>> would let me control the problems. So if I could remove the shock
>> and just replace it with a spacer that would be good. Save some
>> weight too.

I don't get it. Aren't bents immune from pedal bob from the getgo?

> If the thing slams into holes when you pump it up until it doesn't
> work any more, what makes you think that replacing it with a metal bar
> will change that situation?

I was thinking the same thing.

> The idea behind the shock is to keep from jarring you when you hit
> bumps, since you can't climb out of the saddle on a recumbent. Get
> rid of the shock absorber and your body will have to absorb all the
> shock instead.
>
> If you want to replace the shock with a metal bar, just get a metal
> bar about 1/2" thick (or whatever matches your shock) about the length
> of the shock and drill two holes in it.

Not only that, but the mounting bolts will undergo far more stress than when
it had the shock, even when it was pumped up rigid. Even worse, the bent
has far more weight on the rear than an upright, putting lots more stress on
the shock mount. Using a block that's much wider than the prior shock mount
would be a good idea, else the mounting bolts may yield and fracture.

All in all, this sounds like a bad idea.

--
Phil, Squid-in-Training

 

[Steve Knight]

On Wed, 18 May 2005 00:42:00 -0600, [email protected] wrote:

>On Tue, 17 May 2005 23:22:11 -0700, Steve Knight

>If you switch to a bar, you may have to find a machine shop
>to get something the right length and strength that will
>attach to your particular shock mounts.

I figured all I would need to do is take the shock in and have them make a
shaft. but then what do I do without it while they are doing that (G) but if
something was pre made it would be easier.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

 

[Steve Knight]

>They have two stage compression, allowing a stable platform for pedalling
>and open up for bigger hits.
>There are other versions now too - they're quite common in the MB world.

but a really good shock is spendy. I just can't afford to spend that money. the
lack of a shock is not that big of a deal to me.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

 

[Steve Knight]

>If the thing slams into holes when you pump it up until it doesn't
>work any more, what makes you think that replacing it with a metal bar
>will change that situation?
>
it slams into holes because there is no control on the return force. no controls
to slow down the return rate.
going into a hole without it is not a big deal.


>The idea behind the shock is to keep from jarring you when you hit
>bumps, since you can't climb out of the saddle on a recumbent. Get
>rid of the shock absorber and your body will have to absorb all the
>shock instead.

yes but it is not that big of a deal I did not buy the bike for the shock but
that it felt good to ride. I don't have a problem living without the shock. it
would be fine if I could afford a really good shock. but I just can't see
spending 300 for one.

>
>If you want to replace the shock with a metal bar, just get a metal
>bar about 1/2" thick (or whatever matches your shock) about the length
>of the shock and drill two holes in it.
it needs to have machined holes and flats to work well it needs to be accurately
fitted. length is not the critical thing it's the holes. I don't want to mess up
the mounts.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

 

[Wasatch5k]

Steve Knight wrote:
> Anyone know of a bar to replace a shock on my suspension bent? It uses a
> standard shock. I find that if I have enough air in it to get rid of the pedal
> bounce the rear wheel slams down into all holes very hard. I am about 210 but I
> need about 250psi in it to keep the bounce down. If I have about 100 or so PSI
> the bounce is gone and no slamming and the lack of the shock is not that big of
> a deal.
> I don't want to have to spend 300.00 or so for a good shock that would let me
> control the problems. So if I could remove the shock and just replace it with a
> spacer that would be good. Save some weight too.

Go to Walmart and buy a $89 Huffy or Murray with a rear coil shock.
Those things are hard as rocks and compress very little. Swap out the
shocks and your golden!

NC


--

Let the bridges I burn light my way...

 

[[email protected]]

On Wed, 18 May 2005 12:33:08 -0400, "Phil,
Squid-in-Training" <[email protected]>
wrote:

[snip]

>I don't get it. Aren't bents immune from pedal bob from the getgo?

[snip]

Dear Phil,

Have a look at this recumbent pedal-kickback (pogo effect)
suspension calculator:

http://www.kreuzotter.de/english/eschwinge.htm

On an upright with suspension, pedal bob is more a matter of
the rider stomping up and down on the pedals and the
suspension bobbing in reaction to vertical forces.

On a recumbent with suspension, pedal kickback is more a
matter of the rider pushing horizontally on the pedals and
the tightening chain pulling the two halves of the frame
together.

Carl Fogel

 

[sunderland]

Why not just put 500 PSI in there? That would simulate a metal bar
pretty well.

 

[[email protected]]

On 18 May 2005 12:56:23 -0700, "sunderland"
<[email protected]> wrote:

>Why not just put 500 PSI in there? That would simulate a metal bar
>pretty well.

Dear S.,

Unfortunately, 500 psi would also extend the shock to its
upright in-flight position preparatory to landing.

The original poster may not desire a recumbent that imitates
a hot-rod with jacked-up rear suspension.

That much pressure might also lead to failure and deflation,
whereupon the recumbent might switch to imitating a
low-rider.

Carl Fogel

 

[Phil, Squid-in-Training]

[email protected] wrote:
> On Wed, 18 May 2005 12:33:08 -0400, "Phil,
> Squid-in-Training" <[email protected]>
> wrote:
>
> [snip]
>
>> I don't get it. Aren't bents immune from pedal bob from the getgo?
>
> [snip]
>
> Dear Phil,
>
> Have a look at this recumbent pedal-kickback (pogo effect)
> suspension calculator:
>
> http://www.kreuzotter.de/english/eschwinge.htm
>
> On an upright with suspension, pedal bob is more a matter of
> the rider stomping up and down on the pedals and the
> suspension bobbing in reaction to vertical forces.
>
> On a recumbent with suspension, pedal kickback is more a
> matter of the rider pushing horizontally on the pedals and
> the tightening chain pulling the two halves of the frame
> together.

Your explanation made a lot more sense than the link did. Thanks.


--
Phil, Squid-in-Training

 

[[email protected]]

On Wed, 18 May 2005 17:30:43 -0400, "Phil,
Squid-in-Training" <[email protected]>
wrote:

>[email protected] wrote:
>> On Wed, 18 May 2005 12:33:08 -0400, "Phil,
>> Squid-in-Training" <[email protected]>
>> wrote:
>>
>> [snip]
>>
>>> I don't get it. Aren't bents immune from pedal bob from the getgo?
>>
>> [snip]
>>
>> Dear Phil,
>>
>> Have a look at this recumbent pedal-kickback (pogo effect)
>> suspension calculator:
>>
>> http://www.kreuzotter.de/english/eschwinge.htm
>>
>> On an upright with suspension, pedal bob is more a matter of
>> the rider stomping up and down on the pedals and the
>> suspension bobbing in reaction to vertical forces.
>>
>> On a recumbent with suspension, pedal kickback is more a
>> matter of the rider pushing horizontally on the pedals and
>> the tightening chain pulling the two halves of the frame
>> together.
>
>Your explanation made a lot more sense than the link did. Thanks.

Dear Phil,

Below its calculator, the Kreuzotter link does explain
things:

"Chain tension generates a torque upon the swingarm, if
pedal kick back is different from zero, because only then
the chain is able to "pull" the swingarm to a different
angle."

http://www.kreuzotter.de/english/eschwinge.htm

It may be a bit Germanic in phrasing, but the main point is
there. It's a recumbent site, so you can't expect much fuss
about uprights, in which the main pedal force is exerted
downward, not horizontally.

Incidentally, the recumbent suspension bobbing is pretty
much a matter of the frame hunching up like an earthworm
each time that the the rider pushes hard against the pedal.

On an upright, this chain-tightening effect is overwhelmed
by the downward force of the rider's leg thrust--the
suspension squashes and spreads out instead of rising up.

Carl Fogel

 

[Steve Knight]

>Go to Walmart and buy a $89 Huffy or Murray with a rear coil shock.
>Those things are hard as rocks and compress very little. Swap out the
>shocks and your golden!

(G) except for the weight added (G)

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

 

[Steve Knight]

>
>Unfortunately, 500 psi would also extend the shock to its
>upright in-flight position preparatory to landing.
>
>The original poster may not desire a recumbent that imitates
>a hot-rod with jacked-up rear suspension.
>

(G)

>That much pressure might also lead to failure and deflation,
>whereupon the recumbent might switch to imitating a
>low-rider.

I tried it with no air and I got a weird kind of pedal bop not sure if I was
moving or not, it jut felt strange.

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.

 

[[email protected]]

On Wed, 18 May 2005 20:07:52 -0700, Steve Knight
<[email protected]> wrote:

>>
>>Unfortunately, 500 psi would also extend the shock to its
>>upright in-flight position preparatory to landing.
>>
>>The original poster may not desire a recumbent that imitates
>>a hot-rod with jacked-up rear suspension.
>>
>
>(G)
>
>>That much pressure might also lead to failure and deflation,
>>whereupon the recumbent might switch to imitating a
>>low-rider.
>
>I tried it with no air and I got a weird kind of pedal bop not sure if I was
>moving or not, it jut felt strange.

Dear Steve,

With no air, a recumbent with rear suspension should hunch
up just as much or even worse under slow, heavy pedal
forces.

Empty air-shock suspension would offer almost no resistance.

The frame would be sagged as flat as it can go.

So each time the chain tries to pull the rear sprocket and
the front sprocket together, the two halves would hinge
upward at the pivot point.

A solid bar replacing the shock would eliminate this by
locking the two frame halves--no more hunching up like an
inchworm.

As others have pointed out, the solid bar replacement might
end up breaking the mounting points--the frame was
presumably designed for a shock absorber to cushion impacts.

Carl Fogel

 

[AndyC]

"Steve Knight" <[email protected]> wrote in message
news:[email protected]...
>
>
>>They have two stage compression, allowing a stable platform for pedalling
>>and open up for bigger hits.
>>There are other versions now too - they're quite common in the MB world.
>
> but a really good shock is spendy. I just can't afford to spend that
> money. the
> lack of a shock is not that big of a deal to me.
>

Fair enough.

 

[Wasatch5k]

"Steve Knight" <[email protected]> wrote in message
news:[email protected]...
>
>
>>Go to Walmart and buy a $89 Huffy or Murray with a rear coil shock.
>>Those things are hard as rocks and compress very little. Swap out the
>>shocks and your golden!
>
> (G) except for the weight added (G)

IMHO Lightweight is overrated. Most of us should take pounds off ourselves
before we worry about the weight of the bike.

NC

 

[Steve Knight]

>IMHO Lightweight is overrated. Most of us should take pounds off ourselves
>before we worry about the weight of the bike.

I am doing both. but my bent is about 37 pounds it needs a diet too (G)

--
Knight-Toolworks & Custom Planes
Custom made wooden planes at reasonable prices
See http://www.knight-toolworks.com For prices and ordering instructions.