Trek Y3 IGH

Jake

Member
I can't really take any credit for this bike as I bought it used from a posting on BROL. I'd been thinking of building a conversion using an aluminum Y frame and Shimano Alfine hub gearing, but wasn't getting far with sourcing used parts, so when this one came up I saved myself a lot of trouble and cash.

Trek.jpg width: 539px;

The seller was very accomodating and agreed to meet me at a nearby train station. After a wobbly test ride around the parking lot I took the plunge, paid the cash, and shot off along the fortuitiously adjacent Harlem Valley Rail Trail. Managed about 20 miles touching speeds of 20 mph along the straight, flat and uncrowded trail, before catching the train back to NYC.

Back home I'm struggling to perform a hill start on the road outside my apartment, so I have to push it half a block to the crest of the hill, but there is a nearby open space that is handy for practicing figure 8s and low speed maneuvers.The hub gears are a real bonus for learning due to fast low speed / stationary gear changes.

Yesterday I rode my regular RWD recumbent to work, and it felt strange to switch between the two. I figured that to master the Cruzbike I'd have to ride it exclusivly, so I set off for the office this morning on the Trek Conversion. The first 5 miles along the bike path were fine, but the last half mile or so across midtown Manhattan were a bit shakey. Raised a few eyebrows at the office even though they're used to my experimental bike projects.


Early days yet, but I do like the feeling of direct drive to the front wheel, although I do miss a disk brake on the front. With time the dirt tires will be replaced with city 1.25s, 175 cranks switched to 155, the chain will be enclosed with a chainglider, the pedals switched to duel platform/clipless and the seat will be reclined and maybe moved further back.

Is the conversion kit instruction manual available online - all I can find is the list of parts?

Jake
 

Charles.Plager

Recumbent Quant
Hi Jake,
Congratulations and


Hi Jake,

Congratulations and Welcome! You got yourself a good deal. :)

I agree completely with your choice of tires and pedals. And I think you're right that you are best off riding just this one until you aclimatize yourself.

Once you get more used to riding, I do recommend lowering the seat angle. moving the seat as far forward as possible is probably your best shot at getting the lowest angle.

Congratulations again and keep the updates coming.

Cheers,
Charles
 

John Tolhurst

Zen MBB Master
Watch the angle between the

Watch the angle between the centre of gravity and the front tire road contact area. If it gets too vertical, you'll left the rear wheel too easily under hard braking. No more than 60 degrees from the horizontal, so you can brake at 0.5 gravity and meet the EU braking code.

On this bike, the seat is quite high, so there is not a lot of scope for moving it forward.

Keep riding, things will smooth out.
 

Jake

Member
Center of Gravity

The CoG of just the bike is somewhere on a vertical line thru the logo 'Y3' on the frame - this is where I clamp it in my rather flimsy ( for a 45 lb bike) workstand.

According to this article the CoG for a human is just below the navel, although the raising of the arms and knees may raise this somewhat.


Any ideas on how to accurately measure the center of gravity of bike and rider? I guess I could just perform a weighted average of my 175lbs at my navel and the bike's 45lbs at a point somewhere below the logo.

I ride my high racer with a seat angle of around 22 degrees, but was thinking of around 30-35 degrees or so for this bike. I'm keen to move the seat back as that allows me to slide the bottom bracket in - which also raises it, allowing for a more horizontal posture. The current seat post is alumin(i)um, and thus unbendable, so I'm planning on a shimmed 1" steel bmx curved post, and hot set it to get optimum seat angle.
 

Charles.Plager

Recumbent Quant
Hi,
@John:
What I was


Hi,

@John:
What I was proposing (as I'm sure you're aware) was whe moving the seat forward (which pushes the CoM forward), it lowers the angle of the seat (which pushes the CoM backwards as well as lower). I hadn't taken your point into account, so it's good feedback (and after such changes, I don't know where the CoM would be).

@Jake:
Those seat posts are pretty cool. Thanks for the links!

Cheers,
Charles
 

John Tolhurst

Zen MBB Master
Measure the weight on each

Measure the weight on each wheel, and with some math you can tell how far forward the CoG is. Height is probably a bit lower than your navel. Its hard to measure: www.calpoly.edu/~wpatters/wave4.doc.

A good idea is to do some practice emergency stops, and learn what it feels like and how to overcome the Survival Reaction, which is to pull tighter on the brake. The correct reaction is to let the front brake off, you might like to make sure you are able to do that in the middle of a scary stoppie. :D

SURVIVAL REACTIONS are the involuntary adjustments your body makes in situations that it feels are dangerous. "The body isn't smart," says Code. "It's only interested in right now." Survival reactions are bad. They make you brake too hard, turn in too early, tense up, get tunnel vision, chop the throttle and do a host of other things that interfere with good riding. With practice and skill they can be defeated. http://www.superbikeschool.com/news/press-coverage/bike_this_man.php
 

Jake

Member
Seatpost

Charles,
I've just switched my order to a 22.2mm seatpost on the grounds that the seat clamp will fit anywhere along the tube and not just at the end as with the 25.4mm linked above. This should give more flexabilty to seat angle. The downside being a weaker tube and the astronomical price for a 22.2 - 27.2 shim - $20 shipped for a shim!!! As I'd already order the 25.4 - 27.2 shim ( for a far more reasonable $3 shipped), I ordered another 22.2- 25.4 along with the seatpost. I'll post here whether they hold well enough....
Jake
 

Charles.Plager

Recumbent Quant
Hi Jake,
Your first link


Hi Jake,

Your first link doesn't work (or, at least, points to not what I expected it to).

I really like the idea of using these seatposts of Sofriders/conversions to get the seat angle down. It won't work on my Sofrider while I have the trail-a-bike attachment installed, but I'll play around and see what I can come up with.

Let us know how it goes for you (with more pictures, of course!).

Cheers,
Charles
 

Jake

Member
Bent Seatpost

All the parts finally got here, so I installed the bent post. Unfortunatly, anything but a modest 50 degree recline means I can no longer reach the handlebars. Reversing the stem makes them too close. Time to order an adjustable stem.

The 7/8ths post is great as it allows the seat clamp to fasten anywhere along it's length. Far heavier than the straight aluminium post it replaced though. I wouldn't recommend ordering from the ebay seller I posted above as the shim he provides is actually a handlebar shim (ie too short, and no lip).

Jake
IMG_20121001_213947.jpg
 

Charles.Plager

Recumbent Quant
Hi Jake,
Can you take a


Hi Jake,

Can you take a picture of the whole bike? And maybe have someone take a picture of you on the bike with the seat in the "good" position" as well as "too far back"? What happens if you slide the seat forward?

Thanks,
Charles
 

Jake

Member
laid back

Trek2.jpg height: 602px;


The red line shows the 60 degrees from horizontal from the front contact patch, which it looks like my center of gravity is safely behind. That said wheels spins are commen in low gears.
The green line shows the vertical above the rear axel which my head is mostly in front of.
155mm crankset with half step gearing (30/39/42) which works well to split the gaps of the Alfine 8 speed hub.
Rear triangle and front fork color co-ordinated with red reflective tape.
Water bottle racks moved to seat back.
Seat angle is around 28 degrees which is about as low as I want to take it for my 25 minute commute. Beyond that my neck starts to tire. Visibility is still good, due to high seat.
Still room to tinker - I'll try mounting my Bacchetta's handlebars once their replacement arrives.

Jake
 

Charles.Plager

Recumbent Quant
Hi Jake,
Nice picture (I


Hi Jake,

Nice picture (I particularly like the added lines :D) and nice update. You're now low enough that I wonder if a headrest is in your future...

Cheers,
Charles
 
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