GBB #2 - Squishy

[shirk]

The whole thing is steel or just part of it? Wouldn't a 6.5lb steel full suspension be flexy?

It's all steel.

The front end on my first frame isn't flexy, or rather isn't noticeably noodly. So no reason this should feel flexy, it has a more stout downtube.

How would it compare to well engineered carbon frame? Likely much more flex on paper, but I don't think it will have an adverse affect on the trail.

Some older lightweight steel hardtails were flexy, but they were using smaller diameter tubes. Larger diameter tubes are stiffer.

[Tap]

This thread is kinda like mcdonalds, cause I'm lovin it!

[shirk]

Progress...but maybe not enough fast enough.

Front end is all brazed up. Really happy with my brazing, the head tube joint looks great and should clean up nicely.

Creating the bits and bobs for the shock mount and uprights has been time consuming. All items cut out by hand, I have a bad habit of cutting things too long as I don't have much replacement tubing if I screw up. When I rough cut long it means LOTS of time with the hand files.

Image above shows how I'll fixture the rear end with the two sections of L channel. I can "float" the rear axle in space then cut the tubes into place.

[creaky fossil]

Genuine Vault-Tec thumbsup!

All items cut out by hand, I have a bad habit of cutting things too long as I don't have much replacement tubing if I screw up. When I rough cut long it means LOTS of time with the hand files.

Better than having to re-purpose a tube and buy another, though. Carpenter/cabinetmaker cliche, measure 2x cut 1x, etc. Think of your filing finesse gains!

You should see some of my prototype frames and the box of botched cuts that became brazing practice pieces. A junkshow. While yours looks skillful.

I have a good amount of cromo tubing still, if you aim to make something else either for practice or to ride I'd sell you some stuff dirt cheap. Not sure what shipping would cost from me to you, but I'm offering.

[shirk]

I've got several frames worth of main tubes. It's the 1 inch stuff I am using on the rear triangle that I didn't order much extra.

I just need to stop cutting things a country mile long...a city block would be much closer in scale and save some time.

[smslavin]

Progress...but maybe not enough fast enough.

looks great. your brazing looks fantastic. looking forward to seeing how the rest of it comes together.

how are you clamping the tubes when you braze? just c-clamps? is that strong enough to hold the angles while you braze?

[shirk]

No clamping really when brazing.

For the bb to seat tube and the head tube to down tube I slide a length of 1/2inch steel rod into the bb/ht and balance it. The weight and gravity hold the tube tight to the mitre.

Then to joint the sub assy's I use those two lengths of alu L channel to hold the polo mallet in place to the hockey stick. Same for the top tube.


No laser cut, no water jet, no cnc, no mill. Just a hacksaw and files (okay and a drill).

[shirk]

Okay let's pick this back up.

I was rushing to get this frame done for the Whistler EWS, it's first test ride would have been Crankzilla. Early in the week leading up to it I cut my hand, no biggie I thought.


Turns out I got a nasty infection. Had to get put on IV drop for three round of antibiotics to kill the infection. Decided that maybe I should put the project on hold and not work in the garage while I have an IV drip line quick connect in my arm.


Front tri got brazed


Pivot. It's two inset 44mm headset cups pressed into a 44mm headtube. A fork steer was cut off a old junk fork to use as the axle. The swingarm presses against the split compression rings and regular stem top caps on the swingarm to pre-load it all.


Testing for fit with cranks. The pivot location is based on being ridden with a 32t single front ring. I have just enough space between the ring/chain on the top cap providing pre-load on the pivot bearings.


The dropouts where hand cut from plate, I should have spent more time drawing and planning them out. I would then have learned that the pre-cut disc tab that I have would not work. I had to fab up the disc mount tabs from more plate. All this done by hand was time consuming. Next time I'll ask some friends to machine all this for me.


No jig no problem. Ghetto it into place.


Eventually you get here.


Rattle can some flat grey paint.


I started with the Grey on the front, wasn't sure how I'd like it so then hit the back with Flat Black.



Et voila une bicyclette.

It turned out a bit slacker than my initial drawing, my downtube/headtube mitre was off a touch. I did hit my final weight target pretty close, frame painted without shock and mounting hardware is 3.39 kg (7.47 mericans). The bike as built above is 14.41 kg (31.76 eagle freedom units.)


Saturday it got it's first ride. Straight into the deep end. We did a Triple Crown on the Shore, starting on Seymour and hitting all three mountains. Rode 51.4 km and 2144m of climbing.

The fit perfect, my reach and seat tube angle are bang on. I could have gone a bit higher on my stack as it feels perfect with a 10mm spacer under the stem. The beauty of custom is you get to dial that stuff in. Over the years I've always ridden medium's, I'd say my ideal fit is in between a medium and a large.

[LeeLau]

nice work shirk. How gratifying

[smslavin]

awesome. turned out great.

[stuckathuntermtn]

That's amazing. Nice work.

[robnow]

2100m in 50km, nice…is there an elevation profile somewhere on the mtb TC. Nevermind, I see Todd's Strava from 2013.

Brian, did you plan on the 65.5 HA or did it end up with that?

[shirk]

Here is Matt J's Strava. http://www.strava.com/activities/206188804 The route was a bit different from what was ridden last year. There are tons of different variations.

My original plan was 66 but I think I can't really remember if I missed my mark or decided to go with the slacker ha. Either way it's hella slack. The up side is that when I build the next frame I can build something steeper and more xc-ish.

[WaistDeepGroomers]

As someone for whom attention to detail is a weakness, I am totally mesmerized by projects like these that people can do successfully. Kicking ass with life skills!!

[::: :::]

well done!

[creaky fossil]

The whole thing is steel or just part of it? Wouldn't a 6.5lb steel full suspension be flexy?

steel can be flexy or stout it depends on tube diameter and wall thickness, 6.5 would be heavy for a HT of that size, and it's not a complex rear frame compared to a HT rear triangle so not a lot more steel tubing out back. headset at pivot is genius, light weight.

nice work shirk

[scrublover]

Bad. Ass.

It's like a beefier, steel Siniter Gruitr. Want!

I still think if one of the big companies made a *high quality* material, well designed and thought out single pivot line, 4-7" travel range with a couple different models of various travel and geometries, they could spec them out with higher end components, and they'd sell like hotcakes. Don't fuck around with linkages. Give it a nice beefy main pivot system, Thru-axle, internal dropper routing, yaddayadayadda...

Well, probably not. But I like the idea.

Aside: best pedaling bike I've ever felt was my linkaged single pivot Corsair Marque. Rode fucking beautifully (when it didn't have alignment or other QC issues) for the time I had it. The straight up single pivot bikes I've had haven't been bad by any stretch at all, either. I regret not picking up a Gruitr frame when I could have.

[D(C)]

It's pretty awesome to see the finished product, and I can't wait to see it out on the trails. Your idea of using headsets and a steerer tube was a brilliantly simple solution to the main pivot.

How did you go about designing the suspension kinematics and shock placement? Did you go after an existing design or did you have some sort of computer simulation/analysis?

Your overall weight is pretty impressive for a steel frame. What was your process for determining whether the tubing you used will support the required loads? I'd imagine bike manufacturers would use a program like Solidworks to come up with an optimal weight. It's just kind of interesting that you hit the frame weight of an aluminum Devinci Spartan. How do you know if it's over/underbuilt?

[spook]

please gopro your first launch off something big!