Monday, August 06, 2012

Road Frame 5 Complete...

...well sort of complete.  I had an issue when I bagged and cured the frame a few months ago.  The top tube went over temperature in the oven and slightly ovalized.  Not a big deal but one of those things that would bug me knowing it was wrong.  I decided to use the frame for testing and not bother with the final finishing and an expensive paint job.  It's a rattle can finish, good enough to test ride and destructive test later once a replacement has been built.
It's final weight came to 965g.  That's for a 58cm frame with ENVE molded chain stays and individual tubes for seat stays.  I moved all the Shimano Di2 components over and rewired for an internal battery.  I used the following battery which slipped perfectly inside a Ritchey WCS 27.2 carbon post.
Here is the seat cluster with the twin stay tubes and brake bridge.

Stay detail.
Brake bridge detail.
 I used some woven carbon in the joints.  In the right light you can see it clearly through the top layer of uni-directional.  Also note the nice clean brake and Di2 wire routing under the top tube.

More to come in the fall...

Saturday, April 21, 2012

New Frame

I've started on the next road frame.  This one will feature a titanium brake cable guide as well as internal Di2 wiring and battery placement.  This will be the first frame featuring thin twin seat stays.
Here is the BB86 tube with generous Di2 wiring passages cut  to allow the wiring to be tucked up inside the tubes easily.
This frame has a large down tube with an OD of 1.74", pretty close to the 44mm ID head tube for InSet headsets.
The BB joint ready to sand, clean and glue.
 The twin 0.55 OD seat stays are widely spaced which should make it easier to get the carbon to compact between them under vacuum.

Friday, March 16, 2012

Chuck's Bike Assembled

Here is Chuck's new carbon road frame all assembled.

The head tube joints turned out nice and smooth but you can see the uni-directional and faintly the 2X2 twill weave underneath.

The anodized Crumpton dropouts are small and light but also thick and rigid where needed on the hanger.

The BB joint...also very nice looking!

Finally the seat tube cluster with the exit for the rear brake cable.  I'm happy with the way that has worked out.
Yes, that's a nice arch on the cable...
Up next, I start on another carbon road frame with twin seat stay tubes and internal Di2 battery and cabling.

Friday, March 09, 2012

Chuck's Frame Finished

I picked Chuck's frame up from Stefan who did an awesome job with the matte clear over gloss clear theme.  I'll show a few teaser shots now and the rest once the bike is built up.  Here is the underside of the top tube showing the entrance to the titanium brake cable guide tube.

The matte over gloss clear looks really good with the logos.  Subtle unless you look closely.

The surface is smooth and consistent but you can see the pattern of the carbon layers through the paint at the joints.

The underside of the BB with cable guide tube.

Finally the shot Neil has been waiting for...
More to come in the next few days...and the paint weighs 28g for those who obsess over such things.  Total frame weight 1033g.

Tuesday, February 28, 2012

Final Details Before Paint

I spent some time tonight and wrapped up all the last little details before the frame is sent for clear coat etc.
The first thing I did was drill and slot the back of the seat tube.  The slot may be a little short but it clamps well.

I then drilled holes for the down tube cable stops followed by bonding with DP 420 and two rivets each.

Finally I carefully drilled a hole right through the frame behind the BB to guide the front derailleur cable and seal the frame.  Next time I'll get some titanium tubing to avoid possible corrosion issues.  I'll trim the tube flush once the glue sets.

A final light sanding all over with 600grit, a cleaning with alcohol and it's ready for the painters.

Saturday, February 25, 2012

Finished Sanding

I finished sanding the joints on Chuck's frame and I'm pretty happy with the results.  I also started to layout and size the paint mask files on the frame.  Here is there frame with the mock up mask applied.
Next is the head tube badge mask.
I wet down the sanded head tube joints with water to judge how they'll look under clear coat.
With the larger fillets I think the joints came out looking good.
The next step is to install the derailleur cable guides under the BB and under the down tube.  After that I'll bond in a seat post adapter sleeve so a 27.2mm post will slide in perfectly, then it's ready for paint.

Wednesday, February 22, 2012

Bagged Baked and Sanded

The first step after the joints are wrapped in prepreg is to cover each joint in release cloth.  In this case I use a very fine woven coated nylon that lets excess resin through during cure.

Once all the joints are covered they get a layer of bleeder/breather material to distribute the vacuum across the joints and absorb excess epoxy.  Once that's in place the frame is slipped in a vacuum bag.  I use Stretchlon 800 which is a 500% stretchable material that can withstand cure at 250F.  You can sort of see how I form a "Y" shaped bag to slip the rear stays into.  I actually managed to bag and pull a vacuum with no leaks which is a border line miracle!

Here is Chuck's frame hanging in the oven post cure.  You can see the epoxy saturated cloth at the joints.  I added a support bracket and bearing to the oven fan so it didn't try to self destruct this time.
After the oven the frame gets unwrapped which sounds a lot easier than it is.  It requires pliers, a knife and a lot of work.  I ended up with a pretty good looking joint with only a few creases and ribs where the bag halves meet.

Some quick work with a file results in this.  I just take off the little ridges and high spots.  You don't want to be removing carbon.

Post cure weight is about 26g less than before the oven.  That means quite a bit of epoxy was removed.  The prepreg I use is 45% resin to start.  The cure process brings that down significantly.
Here is the BB joint after it was filed then coated in a thin layer of epoxy, sanded and re-coated.  Once this is sanded the joint should be nice and smooth and ready for paint.

Sunday, February 19, 2012

Joint Wrapping

I finished the fillets on Chuck's frame and prepared it for carbon joint wrapping.  The tubes near the joints are sanded with 80grit to roughen the surface for bonding then wiped down with a lot of isopropyl alcohol.
Here are the head tube and seat tube junction fillets.  I made them larger than on previous frames for smoother tube junctions.

I started the joints with 300g/m^2 uni directional carbon.  I use long pieces that wrap around the tubes from multiple angles.

New on this frame is the 2X2 Twill weave carbon.  It draped well over the joints and will add significant strength.

Here is the finished head tube joint.  The final layer is unidirectional long wrapping pieces with a  few cosmetic bits to fill gaps.
This is the first piece I add for the BB joint.  It has a lot of contact with the tubes spanning the whole joint.

I finish the first layer with some diagonal fibers for bending and torsional strength.

After a few layers of 2X2 Twill I finished the joint with some more unidirectional.
I used significantly more carbon forming these joint than in the past.  This will make for a nice strong frame with rigid tube intersections.  It added a little more weight but some of that will come off  when the excess epoxy is pulled out of the joints under vacuum. Still working though the "cosmetics" with each build.  This should be the nicest yet.  We'll see when it comes out of the oven in the next few days.
Coming up next, the frame gets vacuum bagged...

Friday, February 17, 2012

Weight, Alignment and Fillets

Chuck's frame cured over night and was ready to take out of the jig in the morning.  It is starting to look like a real frame.
Glued together prior to adding the fillets, joint wrapping etc it's quite light.  Even with a titanium BB sleeve and internal top tube cable guide it came in at 880g.
I checked the frame alignment and how the rear wheel sits in the dropouts.  Everything looks good.

I added the fillets to the frame joints using a mix of DP 420 and glass micro spheres.  This forms a thick paste that's easy to spread, stays put and makes a light sand-able but rigid fillet.
Next step is to sand the joints smooth then prepare to wrap them in carbon.