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Thoughts on modular dropouts
Hello everyone,
I'm a rookie frame builder.. only have 3 frames under my belt. I'll soon be building a couple more frames, and would like to go the thru axle route. I was thinking of getting these modular dropouts https://www.bikefabsupply.com/rear-d...-x-142-m12x-10 Or these dropouts https://www.bikefabsupply.com/rear-d...th-rack-bosses Anyone have any experience with them? I like the first one because if the hanger gets super damaged for some reason, I can swap it out.. but the other one comes with integrated flatmount.. what dummy thru axle should I get? I've been looking at the ones at Anvil Bikes, and I suppose the one I need is the 142mm x 12 (not syntace).. AND... please excuse my super rookieness and ignorance, I'm intimidated by these flat dropouts (https://www.paragonmachineworks.com/...mm-skewer.html) that you have to also weld what i suppose are called caps.. which I have no clue how to do... I suppose it would be ideal to buy everything from Paragon, since their dummy axles are made to work perfectly with their dropouts.. Thoughts, suggestions? Thanks! |
How well are your frames aligned currently? Through axle drop outs have no room for error in their location. No slight filing to better center/align the wheel.
What rear hub/axle are you intending to run? That will determine the through axle spec and thus the dummy axle. Do you currently set the rear width a tad wide to allow for contraction during the rest of the rear triangle building? The Anvil dummy axles are the most common design/design and some will make their jig accept them or make their own dummies to match the Anvil's design. Andy |
Originally Posted by Andrew R Stewart
(Post 21119351)
How well are your frames aligned currently? Through axle drop outs have no room for error in their location. No slight filing to better center/align the wheel.
What rear hub/axle are you intending to run? That will determine the through axle spec and thus the dummy axle. Do you currently set the rear width a tad wide to allow for contraction during the rest of the rear triangle building? The Anvil dummy axles are the most common design/design and some will make their jig accept them or make their own dummies to match the Anvil's design. Andy From what I gather, with some simple frame alignment checking tools.. they are pretty decent in their alignment, I've never had to file down a dropout to align the wheel. With fear of sounding super noobish.. I suppose a "normal, road" disc hub is a 135mm.. so a Shimano or DT Swiss type hub, with a 12x142mm thru axle |
142 x 12 is the standard for thru axle rear. Anything wider is considered "boost" or "boost plus" or one of the fatbike standards.
The first version, of the dropouts you linked, is going to be difficult to do a disc brake mount. They are not very easy to mount an IS brake mount on either the chainstay or seatstay. For seatstay mounting, an IS tab hangs off the back of the dropout. For chainstay mounting, you need to bend the seatstay , so that it come straight down onto the dropout and gives enough clearance for the brake caliper. Seatstay mounting will work fine with a post mount. I don't have any experience trying to make a flat mount work with those dropouts. |
I know it costs more, but as Andy alludes to, alignment is a one-shot deal with these dropouts. I'd consider using a slider style dropout instead. Paragon has a nice set in stainless (for the part that is fixed to the frame). This allows for post-braze alignment of the chainstay length (via the slider) before the seatstays are attached. Bonus is that the brake mounts are integral to the thru-axle component. Not sure on compatibility with flat mount though. There are adapters to allow flat mount to mate with post mount.
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Originally Posted by David Tollefson
(Post 21119607)
I know it costs more, but as Andy alludes to, alignment is a one-shot deal with these dropouts. I'd consider using a slider style dropout instead. Paragon has a nice set in stainless (for the part that is fixed to the frame). This allows for post-braze alignment of the chainstay length (via the slider) before the seatstays are attached. Bonus is that the brake mounts are integral to the thru-axle component. Not sure on compatibility with flat mount though. There are adapters to allow flat mount to mate with post mount.
Thanks everyone! |
flat dropouts are traditional. Caps are for people that weld and are a relatively recent development if you consider all of bicycle building history. Most people that braze will cut slots in the stays for a flat droput. With 3 frames built, you probably can fill the openings with brazing filler. Probably best to get steel so you can fill with brass if you go that way. I have always thought that flanged dropouts would work better with welding because it's hard to build a decent fillet. People do it, no doubt.
Anvil is still selling dummy axles. Paragon is going to take over that business since Anvil is shutting down. The anvil dummy axles were always sized to work well with Paragon dropouts. I assume Paragon is going to be making identical dummy axles to the Anvil ones. |
Originally Posted by unterhausen
(Post 21119714)
flat dropouts are traditional. Caps are for people that weld and are a relatively recent development if you consider all of bicycle building history. Most people that braze will cut slots in the stays for a flat droput. With 3 frames built, you probably can fill the openings with brazing filler. Probably best to get steel so you can fill with brass if you go that way. I have always thought that flanged dropouts would work better with welding because it's hard to build a decent fillet. People do it, no doubt.
Anvil is still selling dummy axles. Paragon is going to take over that business since Anvil is shutting down. The anvil dummy axles were always sized to work well with Paragon dropouts. I assume Paragon is going to be making identical dummy axles to the Anvil ones. Thats too bad that Anvil is going out of business :( |
Yes, it was a bit of a shock when Don announced it.
One common way to attach tabbed dropouts when welding is to weld it to one side and scallop the other side and weld a piece of tube to cover the gap. Trying to remember who everyone credits with this idea. Here is an example from Engin flickr. The dropout is welded to the back side and a flat plate is welded on the front https://live.staticflickr.com/409/20...e39a8a7a_z.jpg100% machined here at Engin Cycles world HQ and then welded into the final product. Makes me more than proud to say that. by Drew Guldalian, on Flickr |
Welding the brake mount onto the Paragon flat mount dropouts is not a difficult thing to do. I just finished building a frame with them and I fusion welded all around the beveled edge of the brake mount. I used filler to weld around the top of the mounts. The only difficult part was getting the torch into the back side of the rear mount. It is probably easier to weld the mount on before building the frame to have better access for welding and avoid any potential distortion that may cause misalignment.
If price is a concern and you prefer flanged dropouts, the Allotec flat mount dropouts from BikeFabSupply are probably the best option. I wouldn't worry too much about the derailleur hanger. It would take a lot to break that steel hanger. |
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Depending on the size of the chainstays/seat stays you use, Paragon makes these pieces to weld onto flat dropouts. The cone shaped end makes it easy to weld to the stay at an angle. They make them in 3/4" and 5/8" sizes. The also make one that you can weld on to make a flanged end on the dropout.
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Originally Posted by dsaul
(Post 21120698)
Depending on the size of the chainstays/seat stays you use, Paragon makes these pieces to weld onto flat dropouts. The cone shaped end makes it easy to weld to the stay at an angle. They make them in 3/4" and 5/8" sizes. The also make one that you can weld on to make a flanged end on the dropout.
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