Super pumped to see your "BACK20 Break-out" design!
LTJ custom framesets are becoming a reality! (JIG BUILDING)
- Thread starter LukeTheJoker
- Start date
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I had to sacrifice the loop/dual top tube design, but I have come up with something else...
The Renaissance Man
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It's cool that you're taking this on. Good luck!
That's frame is a great idea Luke.
I like the frame, either 20" or 26" they both look good.
thinking 24" might be nice, I ride a 24" a lot and it's just right , right in the middle.
I think you should also make a custom 'adjustable' jig available too.
one that could slide in and out..up and down. movable points to construct almost any type of frame imaginable..something that could compact down to just under 1 meter for easy shipping. With your engineering know how..that would be a top seller..I'm just sayin'.
franco
I like the frame, either 20" or 26" they both look good.
thinking 24" might be nice, I ride a 24" a lot and it's just right , right in the middle.
I think you should also make a custom 'adjustable' jig available too.
one that could slide in and out..up and down. movable points to construct almost any type of frame imaginable..something that could compact down to just under 1 meter for easy shipping. With your engineering know how..that would be a top seller..I'm just sayin'.
franco
Thanks TRM!
Cool plan, but the weight would be the issue then! I like jigs to be really solid with no movement.That's frame is a great idea Luke.
I like the frame, either 20" or 26" they both look good.
thinking 24" might be nice, I ride a 24" a lot and it's just right , right in the middle.
I think you should also make a custom 'adjustable' jig available too.
one that could slide in and out..up and down. movable points to construct almost any type of frame imaginable..something that could compact down to just under 1 meter for easy shipping. With your engineering know how..that would be a top seller..I'm just sayin'.
View attachment 43924
Added some locating plates to the BB mount today:
And then built an overly complicated drop out mount with swivel adjustment and adjustable for different locknut dimensions:
It is too fiddly to use and set up for each frame though, so i will build the simple axle based version next time... Not the first time I have over complicated something thinking it would be better, most of the time simple is best!
And then built an overly complicated drop out mount with swivel adjustment and adjustable for different locknut dimensions:
It is too fiddly to use and set up for each frame though, so i will build the simple axle based version next time... Not the first time I have over complicated something thinking it would be better, most of the time simple is best!
Well, now you've done it.... i've lost interest in the frame, and i'm obsessing over the jig!!!
Seriously, this is getting really cool. I've been thinking of dipping my hand into framebuilding, if i can scrape together enough capital for it, and designing a jig has been pretty heavy on my mind for a while. I'm also fixated on building adult-sized frames with 20" wheels... I wanna build a 20" f/r truck bike, based loosely on VVofA Topanga! geometry....
But, the Back40-style 3-bar looks killer.... especially digging the name "Back20." I'm watching this thread with interest.
Seriously, this is getting really cool. I've been thinking of dipping my hand into framebuilding, if i can scrape together enough capital for it, and designing a jig has been pretty heavy on my mind for a while. I'm also fixated on building adult-sized frames with 20" wheels... I wanna build a 20" f/r truck bike, based loosely on VVofA Topanga! geometry....
But, the Back40-style 3-bar looks killer.... especially digging the name "Back20." I'm watching this thread with interest.
New simple dropout mount, width adjustments can be done with locknuts or washers, not as fancy as the other version, but much simpler to use, still need to drill bolt holes to lock it to the jig:
It will bolt to that diamond upright there which will make sure it is always straight and true to the base, that is why I welded the end supports in the diamond position.
Also made a fork dropout holder, pretty similar but mounted from the base, can be slid along the base and bolted at any distance, and also has height adjustment with a wing bolt, still need to drill the bolt holes in it too:
Next will be the seat tube and stem holders which will mount from the overhead brace and hinge downwards to locate the top of the seat tube and forks. Never seen it done that way before, but if I can make it work it will allow far better access for welding on both sides of the frame than the traditional designs.
It will bolt to that diamond upright there which will make sure it is always straight and true to the base, that is why I welded the end supports in the diamond position.
Also made a fork dropout holder, pretty similar but mounted from the base, can be slid along the base and bolted at any distance, and also has height adjustment with a wing bolt, still need to drill the bolt holes in it too:
Next will be the seat tube and stem holders which will mount from the overhead brace and hinge downwards to locate the top of the seat tube and forks. Never seen it done that way before, but if I can make it work it will allow far better access for welding on both sides of the frame than the traditional designs.
This jig design has been floating in my head for years! Slowly getting refined...Feel free to use any ideas you see and like!
I hope you do, that would be awesome! I am constantly learning, never heard of the Topanga bike, very cool and pretty similar concept!
I might have to build one myself at some point!
Awesome! It has changed a little, it no longer has the twin top tubes, but still has a 3 bar design. I have some sketches, but not any good enough quality to share yet.
Base jig is done, can't go any further until I have a frame built to find the correct angles and lengths for the seat post holder and the stem. Lots of hole drilling and tapping threads today.
Basic dimensions:
Been pricing decals and laser cut pieces, looks like I can afford to get everything set up, just will take me a couple of months.
The finished framesets are going to be awesome though, laser cut headbadges and ID plates and taking inspiration from the old chrome style decals of the late 70's-early 80's BMX's for the finishing touches...
Basic dimensions:
Been pricing decals and laser cut pieces, looks like I can afford to get everything set up, just will take me a couple of months.
The finished framesets are going to be awesome though, laser cut headbadges and ID plates and taking inspiration from the old chrome style decals of the late 70's-early 80's BMX's for the finishing touches...
The Renaissance Man
__CERTIFIED DIVER__ (Open Water & Open Dumpster)
Staff member
Moderator
Pro Member
Looking good! Sometimes working on tooling is just as rewarding as building the parts (speaking for myself at least).
Agreed!Looking good! Sometimes working on tooling is just as rewarding as building the parts (speaking for myself at least).
Sorry for the lack of updates everyone, health went sideways for a bit and I am still waiting on the correct tubing for the seat tubes, somehow got lost between Sydney and here... 
Health appears to be picking up a little, and I am itching to build the first Back20 test frame!
Getting close to finalising the sticker designs too...
Health appears to be picking up a little, and I am itching to build the first Back20 test frame!
Getting close to finalising the sticker designs too...
