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Posted: May 13, 2024 at 10:45 Quote
ethanrevitch wrote:
downhilljohn wrote:
I would like to build a bike. I know how to weld chromoly, fixed my bmx that way cause I cracked it. I want to make a full squish bmx
What's the geo looking like?
could always copy the WTP/fingers crossed rigs

Posted: May 13, 2024 at 13:52 Quote

Now this I like. For most people, most of the time, this would be great road bike.

Some thoughts:

• Fat, fast slicks: Love it, especially the traction on pavement with sand or gravel. A Schwalbe Pro One TL 38 mm would be a good option for a high-spec tire in the intended width range.
• Dropper: I like the long drop - not for dropping into Rampage-worthy terrain, but for a comfortable and safe way to get into a supertuck or maybe getting a foot out to drift a turn on an unpaved surface.
• Where is the 73.9° ESTA taken? Appears to be the centre of the seatpost head when fully dropped ... ? Given that road bikes traditionally have a straight seat-tube without offset (i.e. STA = ESTA at all heights), I would measure the ESTA at the expected saddle height, with the understanding that it will change slightly with saddle height.
• Bar shape: I haven't tried anything with that much flare. My intuition is that it would preclude the use of the hoods; if so, perhaps a narrow flat bar may be functionally equivalent and ergonomically superior. Reading your website, it seems you share my misgivings about this particular bar. Does look stylish, though. 3T makes some great shapes with shallow drops and flare that begins below the lever mount. Note that different widths have different flare shapes, so review the specs carefully!
• BB drop: With such short cranks, it may be possible to push the drop even lower. I'm running 80 mm drop with 175 mm cranks, 26 mm tires, and especially low-profile road pedals: pedaling through corners is sketchy, but there's a unique feeling to being that low, which I've come to like.

O+
Posted: May 13, 2024 at 18:08 Quote
R-M-R wrote:

Now this I like. For most people, most of the time, this would be great road bike.

Some thoughts:

• Fat, fast slicks: Love it, especially the traction on pavement with sand or gravel. A Schwalbe Pro One TL 38 mm would be a good option for a high-spec tire in the intended width range.
• Dropper: I like the long drop - not for dropping into Rampage-worthy terrain, but for a comfortable and safe way to get into a supertuck or maybe getting a foot out to drift a turn on an unpaved surface.
• Where is the 73.9° ESTA taken? Appears to be the centre of the seatpost head when fully dropped ... ? Given that road bikes traditionally have a straight seat-tube without offset (i.e. STA = ESTA at all heights), I would measure the ESTA at the expected saddle height, with the understanding that it will change slightly with saddle height.
• Bar shape: I haven't tried anything with that much flare. My intuition is that it would preclude the use of the hoods; if so, perhaps a narrow flat bar may be functionally equivalent and ergonomically superior. Reading your website, it seems you share my misgivings about this particular bar. Does look stylish, though. 3T makes some great shapes with shallow drops and flare that begins below the lever mount. Note that different widths have different flare shapes, so review the specs carefully!
• BB drop: With such short cranks, it may be possible to push the drop even lower. I'm running 80 mm drop with 175 mm cranks, 26 mm tires, and especially low-profile road pedals: pedaling through corners is sketchy, but there's a unique feeling to being that low, which I've come to like.

I would expect that the 73.9 sa is at full saddle height. From memory I think Peter's SA is driven angle from saddle location as the driver. Knowing the saddle height, exact saddle dimension, and the required set back from saddle tip over the bb the SA is then just a driven number no a driving number.

photo

Here on his print you can see the saddle tip is 41mm off the bb center.

I started doing it this way a number of years ago after a discussion between Peter and Sam from Naked outlining this method in a FB discussion.

Posted: May 13, 2024 at 19:38 Quote
I was thinking 21inch top tube with a pivot right on the crank spindle. Haven't decided on the rest of the frame
ethanrevitch wrote:
downhilljohn wrote:
I would like to build a bike. I know how to weld chromoly, fixed my bmx that way cause I cracked it. I want to make a full squish bmx
What's the geo looking like?

Posted: May 13, 2024 at 22:11 Quote
shirk-007 wrote:
I would expect that the 73.9 sa is at full saddle height. From memory I think Peter's SA is driven angle from saddle location as the driver. Knowing the saddle height, exact saddle dimension, and the required set back from saddle tip over the bb the SA is then just a driven number no a driving number.

That would be sensible - and I hope it's the case - but that's not how the drawing looks.


shirk-007 wrote:
Here on his print you can see the saddle tip is 41mm off the bb center.

I started doing it this way a number of years ago after a discussion between Peter and Sam from Naked outlining this method in a FB discussion.

Minor point, but the saddle rear (excluding any cosmetic nonsense) is the more relevant datum, especially with the current trend toward truncated noses.

Posted: May 14, 2024 at 5:29 Quote
R-M-R wrote:
pvd666 wrote:
Road+...

• Where is the 73.9° ESTA taken? Appears to be the centre of the seatpost head when fully dropped ... ? Given that road bikes traditionally have a straight seat-tube without offset (i.e. STA = ESTA at all heights), I would measure the ESTA at the expected saddle height, with the understanding that it will change slightly with saddle height.

Thanks.

The ESTA is located at full pedaling height to the reference location on the saddle where the sit bones contact. Notice that I'm very specific about where that is on the saddle. While this is not a perfect number that is reproduceable across all saddles, it's good enough to place the point withing a few millimeters. Let's say that I chose the correct point.

Even if the actual seat tube is coincident with the center of the crank axis and a zero offset seatpost is used, the ESTA will be different that ASTA generally by a degree (or more) steeper. See the example below with a very conservative 'gravel' bike that I recently measured for a friend.

photo

This is why I put so much effort into prints. Having actual rather than ghost values is key in development.

Posted: May 14, 2024 at 5:43 Quote
pvd666 wrote:
R-M-R wrote:
pvd666 wrote:
Road+...

• Where is the 73.9° ESTA taken? Appears to be the centre of the seatpost head when fully dropped ... ? Given that road bikes traditionally have a straight seat-tube without offset (i.e. STA = ESTA at all heights), I would measure the ESTA at the expected saddle height, with the understanding that it will change slightly with saddle height.

Thanks.

The ESTA is located at full pedaling height to the reference location on the saddle where the sit bones contact. Notice that I'm very specific about where that is on the saddle. While this is not a perfect number that is reproduceable across all saddles, it's good enough to place the point withing a few millimeters. Let's say that I chose the correct point.

Even if the actual seat tube is coincident with the center of the crank axis and a zero offset seatpost is used, the ESTA will be different that ASTA generally by a degree (or more) steeper. See the example below with a very conservative 'gravel' bike that I recently measured for a friend.

photo

This is why I put so much effort into prints. Having actual rather than ghost values is key in development.

We need to meet-up one day and chat bikes, Peter. I think we'd have fun! I don't agree with all of your ideas, but gosh darned I love what you do!

Posted: May 14, 2024 at 6:02 Quote
gabodude wrote:
We need to meet-up one day and chat bikes, Peter. I think we'd have fun! I don't agree with all of your ideas, but gosh darned I love what you do!

Awesome! We did talk at NAHBS one time. It may have been that year you got a prize.

Posted: May 14, 2024 at 9:39 Quote
So many legends in this thread!! Salute

Mod
Posted: May 14, 2024 at 10:16 Quote
R-M-R wrote:

Now this I like. For most people, most of the time, this would be great road bike.

Some thoughts:

• Fat, fast slicks: Love it, especially the traction on pavement with sand or gravel. A Schwalbe Pro One TL 38 mm would be a good option for a high-spec tire in the intended width range.
• Dropper: I like the long drop - not for dropping into Rampage-worthy terrain, but for a comfortable and safe way to get into a supertuck or maybe getting a foot out to drift a turn on an unpaved surface.
• Where is the 73.9° ESTA taken? Appears to be the centre of the seatpost head when fully dropped ... ? Given that road bikes traditionally have a straight seat-tube without offset (i.e. STA = ESTA at all heights), I would measure the ESTA at the expected saddle height, with the understanding that it will change slightly with saddle height.
• Bar shape: I haven't tried anything with that much flare. My intuition is that it would preclude the use of the hoods; if so, perhaps a narrow flat bar may be functionally equivalent and ergonomically superior. Reading your website, it seems you share my misgivings about this particular bar. Does look stylish, though. 3T makes some great shapes with shallow drops and flare that begins below the lever mount. Note that different widths have different flare shapes, so review the specs carefully!
• BB drop: With such short cranks, it may be possible to push the drop even lower. I'm running 80 mm drop with 175 mm cranks, 26 mm tires, and especially low-profile road pedals: pedaling through corners is sketchy, but there's a unique feeling to being that low, which I've come to like.


I've had great success with specialized nimbuses (nimbii?) they are shockingly fast and grippy, feels like riding on a cloud

O+
Posted: Jun 4, 2024 at 20:57 Quote
mrti wrote:
photo

Reminds me of Mongoose freedrive. Love it.

Would be interesting to see how it feels with the idler vs how mongoose floated the bb.

If you don't want to model and print a mudguard for that shock get some thin kydex and bend one to attach with a ziptie.

Posted: Jun 5, 2024 at 1:07 Quote
Such a clean and elegant design Smile

Posted: Jun 5, 2024 at 12:56 Quote
couple years in the making, but I think I'm done?!

photo

photo

photo

photo

Posted: Jun 5, 2024 at 15:24 Quote
Very cool! Seems like carbon front triangle and seatstay with 7075 chainstay and linkage? Curious what bearing sizes you are using and what your kinematic goals were.


 


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