Blackhawk GTA

GoldenMotor.com

Dogtown Burner

New Member
Sep 15, 2011
349
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Los Angeles
For simplicity sake I'm skipping the numbers and letters and all the confusong nomenclature. theres 2 skyhawks. stub and no stub. i am going to be calling the stub GTA, and the no-stub GTS for "straight" downtube.
Here we go on an adventuresome endeavor. a dual disc brake daily driver with a few small power modifications. This bike was a fun build, and I love the flat black color. it came out real nice from the powdercoater in Gardena. You'll see our new chief mechanic as well...
 

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Dogtown Burner

New Member
Sep 15, 2011
349
3
0
Los Angeles
After realizing that the GT has a 1-1/8 steerer tube and the monark II forks are 1", we went with the Felt Abraham Linkage front end. Part laziness, part wanting to try something new. Unfortunately for us, the Felt product is a classic themed product. No disc brake mount exists, so I employed Ken Warren of KW machine to manufacture a new line of felt springer disc brake mounts. we will be selling them on our websites exclusively. (shop.jakebike.com) and KWmachineworks.com. Also, the rear disc is a tad hassle. We use a kings top hat and offset sprocket with many spacers and hoo haws to get the caliper and the chain to agree on space management. We also made a rear bracket for disc caliper mounting. So for those millios of dudes wanting Skyhawk GT's with dual discs, we have your solution. Also a universal motorized bicycle rear hub is in the works. stay tuned for a dual disc mount single speed right freewheel , left solid sprocket mount rear hub this spring. heres some sneak photos
 

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Dogtown Burner

New Member
Sep 15, 2011
349
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Los Angeles
Here we have some assembly shots. the tricky thing about the rear brake is SPACE. theres a finite amount of it back there. as you can see in this picture, a kings offset sprocket with a large (1/4" ) offset top-hat, and the disc rotor is spaced away from the tophat with those 5mm kit washers. The problems that arise are 1) CHAINLINE- with so much offset, the sprocket is kissing the spokes. so 2.5" tires make chain alignment tough. thin chain helps this, you'll notice. 2) CALIPER CLEARANCE: the fatness of the caliper puts the adjuster nut (featured center frame 2nd photo) right against the sprocket. with a 40t sprocket and 160mm rotor, the orientation of those sizes is key, as the adjuster nut would hit the chain if the sprocket was any smaller. the adjust nut rides just under the chain. 2thou clearance!!! (photo 3) [recall the gold "SKYHAWK GT BUILD" Where we mentioned "aircraft tolerances, gentlemen" ?]. This bike is a replica in different skin. The solution to all this- make a better bracket; one with an offset to kick the caliper out to the left and allow for the caliper hangers' thickness to not rub the rotor. the design i came up with is like a 3 layer design platform made from one solid piece of 7075 aluminum. the key is keeping the axle mounting portion just under 1/8" so the dropouts and frame dont get stretched too far out and hide the axle threads.
Then, the caliper mount gets wide and protrudes outside the frame dimension width. the brake mount portion of it is cut away for the cal. hanger.

fairly intricate piece. if you need mounts to do this type of thing, we will be making a production run this week, and they'll be for sale on shop.jakebike.com, and KWmachine
 

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maurtis

New Member
Dec 14, 2011
707
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Kyle, TX
Awesome build, talk about tight fit with the rear setup! While looking at the frame I kept thinking... a vertical 79/99cc Preddy would look nice in there too, then I saw your cameo shot. Definitely makes it easy to picture the Preddy in there now! I wonder how the AL frame would hold up to the bigger motor?

Very cool and inspiring work. One day I hope to progress past the zip ties and dremel stage of customization.
 

runnermike

Member
Nov 18, 2012
936
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16
Sanford, FL
Is that the exhaust that you sell on your site, just reconfigured? Im digging it. Im in the process of finding a good exhaust for my Skyhawk frame build.
 

Scott.D.Lang

Member
Jan 1, 2013
406
2
16
Chicago
very nice in the future Ill have to contact you guys I know some day I want to use disk breaks the stock ones on my bikes scare me with out a motor sometimes lol
 

SuperDave

Member
Sep 24, 2011
179
0
16
Panama City Beach, Fl. USA
Sweet build. I have a GT2A, been thinking about a disc for the rear, for now I just got a coaster brake. But I run a 415 chain, so I doubt the caliper would fit. Any way you could rotate the caliper to hang in between the framerails? I'm sure there would be clearance then without interference from the chain.
 

Dogtown Burner

New Member
Sep 15, 2011
349
3
0
Los Angeles
Sweet build. I have a GT2A, been thinking about a disc for the rear, for now I just got a coaster brake. But I run a 415 chain, so I doubt the caliper would fit. Any way you could rotate the caliper to hang in between the framerails? I'm sure there would be clearance then without interference from the chain.
we have the caliper mounts now, but a 41 chain is needed, as well as thin sprockets with the top hat adapter