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BMDS - (garage framebuilding)

shirk007

Monkey
Apr 14, 2009
307
110
Built up yesterday for first ride.







63ha. 75.5sa. 465mm reach. 440mm chainstays. 1260mm wheelbase. 327mm bb height. 160mm fork. 144mm rear travel. Suspension is progressive with a LR from 3.05 to 1.78. Shock is a Super Deluxe 230x65.

This is the second full suspension I've built, the first one being a classic single pivot. I wasn't happy with the linear nature of the straight single pivot and worked out a linkage that gets a progressive LR. This linkage works the same way as a TR500/Pulse/old Turner DHR, I fiddled around to get it to work with the shock stuffed as low and back in the frame as I could. The links need to go back into the mill and get cleaned up, they were made at 4am Sunday morning so I could ride it this weekend.


Leverage Ratio

The pivot location is set to give it a slightly high amount of Anti-Squat than the norm of 100% that most bikes are using. Here in the Sea to Sky everything is pretty much straight up then straight down so the high anti-squat will climb firm without needing to lock out the shock and I don't really care that it will firm up if/when I get on the pedals on a downhill.


Anti-Squat

Anti-rise is...whatever who cares. With the single pivot design this is what it is once I set the main pivot to get the anti-squat where I wanted it and as much rearward travel to the axle path as i could (limited to what you can do here).


Anti-Rise

I am not an upstart framebuilder looking to sell frames, just a guy building in my garage for now. I'll post more on the process and my limited tooling and some of the design work.
 
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chris_f

Monkey
Jun 20, 2007
265
228
That's pretty sweet. Report back on how it rides as soon as you've given it the beans.
 

dump

Turbo Monkey
Oct 12, 2001
5,434
231
Congrats. Shirk007 is my bike-building role model... except he actually builds bikes.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
15,864
957
01776
help me out here, what's the difference between the purple and blues lines?

looks like a great job...spot on for efficient kinematics, if the first blue line is your actual leverage ratio!
 

shirk007

Monkey
Apr 14, 2009
307
110
help me out here, what's the difference between the purple and blues lines?

looks like a great job...spot on for efficient kinematics, if the first blue line is your actual leverage ratio!
Ignore the thin purple lines, the actual bike is thicker blue line. I had anther version of the frame out in Linkage and was messing around with the pivots and rocker, I should have closed it when I exported the files.

The LR progression (3.05 to 1.77) is just a touch lower than the latest Capra 29'er (3.5 to 2.15). Another reference is the RM much loved GG Megatrail at 2.75 to 2.3.
 

shirk007

Monkey
Apr 14, 2009
307
110
WINNER!

love homemade full suspension bikes, no matter what they look like

oxy-acet brazing? very interesting
Oxy-propane brazing.



I use an oxygen concentrator instead of bottle oxy, so I never need to get a bottle filled. The concentrator was bought used from a medical supply place as a scratch-n-dent unit for about $300 Canadian. The generator is the same kind of unit they hook grandma up to when she needs oxygen at home long term.

With the propane I use "mixed fuel" tips in my torch and the flame is a touch cooler than oxy-acet and not as sharp but still have tons of heat for brazing. A framebuilder named Doug Fattic did a boat load of research on this and shared it on one of the frame building forums. Most guys braze with oxy-acetylene,
 

TrumbullHucker

trumbullruxer
Aug 29, 2005
2,207
585
shimsbury, ct
Oxy-propane brazing.



I use an oxygen concentrator instead of bottle oxy, so I never need to get a bottle filled. The concentrator was bought used from a medical supply place as a scratch-n-dent unit for about $300 Canadian. The generator is the same kind of unit they hook grandma up to when she needs oxygen at home long term.

With the propane I use "mixed fuel" tips in my torch and the flame is a touch cooler than oxy-acet and not as sharp but still have tons of heat for brazing. A framebuilder named Doug Fattic did a boat load of research on this and shared it on one of the frame building forums. Most guys braze with oxy-acetylene,

Very Very cool.. I've heard of oxy-propane but never read any "reviews"

Any reason why you didn't TIG? Just curious
 

shirk007

Monkey
Apr 14, 2009
307
110
Total cost for my brazing rig was about $500. No way to get into a tig unit at that price. Also with brazing you have a wider margin of error when you are learning. With tig you can overcook a joint pretty easy and with brazing you really gotta fall asleep at the wheel to get as much heat into a joint as quickly. I also prefer the look of brazing vs tig. Strength of joint isn't an issue, the tube should fail long before a proper brazed joint.

With oxy-propane and the multi-fuel tips you generally need one tip size up to get the same heat as oxy-acetylene and then you end up a bit broader flame. The broader flame will partially drive how the fillet looks, I don't think I could get the super tight small fillets that some guys are doing with my torch.
 

dump

Turbo Monkey
Oct 12, 2001
5,434
231
Agreed on the oxy-propane setup vs. a tig setup costs. If you're purchasing, and doing it at home, a tig setup will run you $2,000 or more (which is roughly the price of a spoke these days, but I digress.) One day soon, I will dip my toe in this direction. God knows I've done all the reading.
 

canadmos

Cake Tease
May 29, 2011
9,516
5,234
Canaderp
Pretty sweet looking. Props need to be given.

Whats with the stickers on your wheels? Having them not be symmetrical would bug the shit out of me. :busted:
 

shirk007

Monkey
Apr 14, 2009
307
110
The seat tube is also bent. Cutting a big chuck out of the unique seat tube was a measure 50x cut once ordeal.

Seat tube came from PVD.

https://www.peterverdone.com/professional-seat-tube-design/

My first attempt at this frame was a bit different.



The seat tube was made from three section. I started this front end before I got my milling machine late last summer. It was a bit of a nightmare to try and build and align with limited tooling. It ended up that the bb, main pivot, and upper pivot are all out of alignment. Oh and it doesn't help that I made the classic noob builder mistake and welded in the threaded bb backwards.

Shortly after finding out the bb was in backwards I jumped on getting my hands on a few of Peter's special run of seat tubes. This would allow me to offset the seat tube as needed and still land it on the bb.

Early this spring Peter Daam of Daam cycles posted this frame in progress.

https://www.instagram.com/p/BiCg2sRBY-q/?taken-by=daambuilt

He flipped the bent downtube around to create more space for a bike packing frame. It was another light bulb moment for me that I could do the same and create more space to drop the shock in the frame and run a water bottle on the top of the downtube instead of up under the toptube like Starling does.
 

bagtagley

Monkey
Jun 18, 2002
205
9
VA
Nice work, man! So badass.

I just discovered that I can access the engineering department's welding/cutting/bending equipment. I know I've asked you this before, but what's the best place to start as far as know-how?
 

roflbox

roflborx
Jan 23, 2017
2,872
658
Raleigh, NC
Nice work, man! So badass.

I just discovered that I can access the engineering department's welding/cutting/bending equipment. I know I've asked you this before, but what's the best place to start as far as know-how?
Local community college / tech school might offer welding classes.
 

4130biker

PM me about Tantrum Cycles!
May 24, 2007
3,904
441
Lizard Town
Nice work, man! So badass.

I just discovered that I can access the engineering department's welding/cutting/bending equipment. I know I've asked you this before, but what's the best place to start as far as know-how?
MTBR’s frame building forum is a wealth of knowledge with some big and small builders lurking about... Just make sure to read read read and search everything you can. The mod can get a bit cranky about re-answering new builder questions, and especially to the people who “start” but never build anything.... Best to post pictures of progress/practice after reading, then questions IMO.
 

shirk007

Monkey
Apr 14, 2009
307
110
New bike.







Hopefully I get one test ride in before I feed through the Whistler EWS80 torture test machine on Saturday.
 

shirk007

Monkey
Apr 14, 2009
307
110
Had a look on the start list last night and saw you. Looks like we're a fair bit earlier. Did you put anyone's name in to ride with? Coleman and a few of us are riding together.
 

kazlx

Patches O'Houlihan
Aug 7, 2006
6,565
1,361
Tustin, CA
Awesome job man. Definitely on my to-do list one of these days. I have a CNC mill in my garage if you need linkages or parts like that.