On 2017-10-24 13:41, wrote:
On Tuesday, October 24, 2017 at 12:38:15 PM UTC-7, Joerg wrote:
On 2017-10-24 12:28, sms wrote:
On 10/24/2017 12:06 PM, Joerg wrote:
After the boom of my otherwise quite tough seat post rack
buckled during a gnarly ride with heavy load I modified
things:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

The seat post clamp is very beefy and I was custom-made in a
machine shop. It has old tube snippets laid inside. Four 1/4"
bolts. The strut is U-shaped aircraft-grade aluminum and bolted
to a false bottom with 6mm screws. The false bottom can be seen
in the old version:

http://www.analogconsultants.com/ng/bike/Battbox2.JPG

The panniers are held on with a 0.200" Perspex plate, slightly
spring-loaded, so they don't whop up and down during rough
rides.

The little box on the strut contains a four-cell 18650 battery
block to keep the lights going. I will add an electronics box
with more features to tie in the MP3 player and maybe a cell
phone charger. Or maybe a GPS some day.

I also installed the longest seat tube I could find (400mm).
Aside from allowing some serious loads to be carried this strut
has also completely eliminated the frame and seat tube
squeaking. On a scary steep downhills I can now even
temporarily plant my behind on the rack.

I SPIT on seatpost mounted racks.


Well, how else do you propose to do that on a full-sus MTB? Bolting
it to the diagonal frame struts is out because it can quickly
destroy those with heavy loads. Also, the whole cargo would become
unsprung mass, making for a very uncomfortable ride and possibly
damaged cargo.

It appears that you've done a good engineering job of what you were
trying to accomplish. But that makes the entire mess so heavy that
you must have abs like the Hulk.


The bike before the mod but with rack and panniers was around 40lbs
total. The strut, clamp and miscellaneous hardware probably weighs
another 2lbs so the added weight is down in the noise. Another addition
for increased ruggedness was regular but slit tubes over the tire
liners, fairly beefy ones, not cheap tubes. The slit is crosswise and
only as wide as the Mr-Tuffy liner, at the point where I cut out the
valve. So each tire now has:

1. Heavy tube with 0.160" wall thickness towards running surface (wish
it was all around). Those weigh about 1lbs each.

2. Mr.Tuffy liner sleeved into a beefy but not thornresistant tube to
prevent chafing. Adds 0.100" more that thorns would need to penetrate.

3. Knobby tire with thick rubber-coated side walls, inflated to 90% of
allowed max pressure or about 55psi.

Flats? What's that? Oh, yes, the phssseeeooouuu sound that makes other
riders pull off the trail ...

Considering that I weigh over 200lbs it's not that bad except when
having to lift the MTB over a fence or into a truck.

My abs aren't that great but my leg muscles have grown considerably
after I started mountain biking. Which resulted in my weight first
dropping and then climbing again while the waist line kept shrinking.

The road bike with its rack isn't far behind but doesn't have a top
trunk, just panniers. It has thick tubes and now also liners. On either
bike I carry a full tool kit, a spare tube (so far always for other
riders), central battery, a heavy lock, lights, lots of water, sometimes
a homebrew IPA, some food, tow rope, dog leash, and some other small
stuff. No more growlers though since I started brewing.

--
Regards, Joerg

http://www.analogconsultants.com/