Blue Dream: Maxarya Ray 2 Semi Recumbent w/high eff mid drive

[neptronix]

I rode the bike with the eccentric front bottom bracket in the diagonal & foward + down position.
It feels like the seating position goes forward more in this position.

I did some modifications to bring the chainline more inline on the front and rear chains, and cleaned the chains and relubed, and this seemed to make a tiny difference in pedaling efficiency up the 8 mile climb.
Either that or i am developing better musculature, which is possible because i was very out of shape until this month.



The wiggly-ness was half as intense, almost liveable, but felt a little sketchy at 30mph. Disconcerting but not dangerous.
0-7mph cross winds were present.

I notice that most of the wiggly-ness at high speed stops when i stop pedaling.
10mm longer cranks are not helping.
A taller front end is maybe not helping.
~1lbs of water bottle hanging 1 inch off-center on the handlebar isn't helping.



Maybe there is such a thing as moving forward too much and i've extended leg weight out way too far, and also too wide.

I have done these modifications and will retest tomorrow:
Water bottle delete
Adjust the cranks back to the 'down' position.
Get the pedals inwards about 2mm. i have room to eliminate more material off the cranks to make that happen and eliminate the BB spindle shims.

Here's another aspect i can tackle later:
I could move the seat down almost an inch to make up for this extra height i've added by redrilling it.
It would get me closer to the cannondale geometry that sat me lower.
Now that i've raised the bike, it would help my CoG to get that seat lower.

The cannondale also had very low handlebars. So i've lowered and pulled back mine a smidge.

Will retest. Fingers crossed!

 

[neptronix]

I found this gold from @tigcross some pages back in this thread..

"The other item to bring up is crank length. I know you've mentioned that you have some issues with your legs and prefer longer cranks, but I wanted to let you know about why shorter cranks are standard on the better recumbent bike.

It has to do with inertia: on an upright bike, the inertia from the rider's legs pumping up and down is 100% directed into the bottom bracket and the ground. On a recumbent the inertia is split, because the rider is horizontal, some of the inertia from the legs is going forward into the BB, but some of it is going up and down, this causes a bounce in the bike as the legs bounce up and down on each pedal stroke. It is for this reason that many recumbent have shorter cranks, because it makes for less up and down movement of the legs and less bounce.

Most conventional bikes need longer cranks because they need enough leverage to allow the rider to pedal hard and stay in the saddle. A recumbent does not have this problem because the rider has a back-rest to push against. The downside is that recumbent riders often injure their knees because they can put to much pressure through them because of the back-rest to push against (this is what led me to develop the GCD for the Electrom).

In your case shorter cranks would also help with fork-crown clearance. I'm running a set of 154 mm cranks on the Electrom and they feel great."

..and of course he was right.


I have another thing going on here... a 127.5mm bottom bracket versus the stock, quite narrow, 115mm wide.
Half an inch wider but this is worsening the human 2 cylinder engine problem.
I took crank length from 170mm to 180mm, creating +10mm of up/down motion.

With these long cranks i am also managing to piss off my cartilage a bit on steep climbs. This is more of an issue of not ideal gearing though.

I could revert to 170mm cranks, but by doing so, i lose 10mm of reach and worsen the weight balance.
But with +2 inches of swingarm, the weight balance problem improves dramatically, and now i just have to solve the reach problem, with a different handlebar configuration ( not rocket science to do )

So what i think is that the longer swingarm is basically a requirement for riding this bike at higher speed.

Anyway let's move this human engine backwards to the previous setting and see how it goes at 30mph.


I got an email back from uding.
The H20 fork is 162mm wide. My current Spinner Grind is 152mm wide, with 4mm shaved off. The suntour 20mm forks are a about 167mm wide.
The H20 fork also has another 7mm of offset, on top of the +10mm of travel. And 5mm wider stanchions, so the stiction should be lower.

With the right bottom bracket position ( a little bit backwards and down ) and 165mm cranks with some shaving of the outer edge, i believe i could run this fork. But i then absolutely require this 2 inch or 51mm longer swingarm.

Back to the drawing board it goes..

 

[neptronix]

So i experimented with the downward and a little bit backwards position on the eccentric BB.



I also pumped the front suspension up another 10psi to raise the front. I noticed it got down to 35psi somehow.

I also deleted everything off the handlebars, and as you see, i have another stem that pushes things backwards to compensate for the seat going backwards.



How was the ride?


I went into some medium strength headwinds downhill at 30mph + spinning the pedals at 90rpm and the bike performed admirably.
The wobble when pedaling is very minor now; it's not worth it to stop pedaling to get better stability at higher speed.
It also wants to track straighter on it's own, without handlebar input.

I think what happened is that i re-centralized my weight by going back 3-5mm after going 10mm forward before.

The sad thing is that the NVH got worse while the handling got a bit better.
So mid ride i had to take the front tire from 50psi back down to 40.
Sad, but i did loose a little NVH goodness. It's just acceptable now.

Well, this is kind of surprising. i've only been moving the cranks / eccentric BB/ seat +/- 15mm this whole time.
It's like there's a sweet spot on every adjustment whose range is a few millimeters.

I think this explains a lot of things about people's experiences on semi recumbent bikes.
A small difference in the wrong parameter can completely destroy the riding experience.
And this bike has, by far, been the most difficult to dial in of any semi recumbent i've owned.

I think i'm within a millimeter of the goldilocks zone for weight balance here and look forward to this longer swingarm and 10-15mm taller fork to extend both the front and rear wheelbase.

I think this bike is confident up to about 30mph. I really need to unlock another 7mph to hit my top speed goal though.

 

[neptronix]

Two other things.

The h20 fork + 165mm crankarms might work, only if i move my eccentric BB to the backwards and slightly up position.
Here's the OE 170mm crankarm the maxarya came with, with the eccentric BB in that position:


165mm would require that only the edge of the pedal outside the bolt, plus a small part of a wider fork's crown be removed.
This would cut the strength loss 50/50 and should work.
This requires the +2 inch swingarm because i'll get pushed back 30mm.
The only problem is that the H20 fork is 10mm wider, which means i have 5mm of metal to remove on each side.

I think this fork with +5mm wider stanchions could tolerate losing half the metal on the side.
We will also cut off 90% of this cable organizer on the left, leaving the other 10% as a strength booster.






All existing mounting points for storage disbalance this bike substantially.
I considered something like a backpack on the seat, but the weight could add some pendulum-ing effects on the rear that are undesired.

After clipping the excess length of the plastic ties that hold the seat mesh on, it was revealed to me that the seat has a pretty good volume inside.

I think that if i could make a pocket that dips halfway in, i could confidently carry tools, water, tubes, patch kits, and other things i need for long distance touring.. without having to worry about it affecting the handling of the bike, or inducing much of a crosswind penalty.

Other than right under the seat, this seems like an ideal place to put things, as long as they're no bigger than 1.5 inch diameter.