My dropouts aren't long enough for sufficient chain clearance. Is there anything I can do to extend them?

I thought about bolting on some aluminum plate, but that will modify the OLD cause the plate will have to be either outside or inside the original dropouts. Seems like there should be a part sold for this.

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Can we see a picture of the entire bike? I'm thinking your best bet might be an idler to re-route the chain.

I see more than one problem it appears. it looks like you are trying to install a Sturmey Archer 8 speed hub on a large wheel frame using a very small front chainring to give an adequate low gear. Also trying to install it in a frame with vertical dropouts and no chain tensioner as well as trying to use anti rotation washers not intended for vertical dropouts. The amount of drop from the chainstay to the dropout is one major cause of your problem it appears in addition to the others I have mentioned.

No easy solution that I know of as basically your hub setup and frame are just not compatible with one another. It might help if you gave a wider view photo showing the crankset and complete chain line (basicallly the whole center and rear of the bike) but from what I can see from the photos so far the frame is just not compatible with what you are trying to do.

Looks like a DH bike to me, if thats the case u need to add the rollers in the frame and a special tensioner in the back to handle the extra slack in the chain as dan and tat mentioned.

It is a recumbent I believe and the chain appears to be routed incorrectly.

https://www.bacchettabikes.com/bikes/...e-bikes/strada

That looks right on, you even got the color right.

Actually the idler is the problem that's being solved here. It's noisy and inefficient and it creates other problems I'd rather not get into.

The solution is to use a small chainring, which in turn required a custom wheel with an internal hub and a custom sprocket and a custom chain. Although I painstakingly measured clearances ahead of time, somehow in the end things didn't line up (I think because things flex under load).

So now I've discovered I need a new frame (although it will take a few more hours before I know if it will need to be a custom built frame or a stock frame). However, since I've already spent hundreds of dollars and hundreds of hours, I don't want to invest more time and money on the frame unless I'm sure I'll be happy with the result. Therefore I'm looking for a temporary solution to test out what I've done so far and for that I think extending the dropouts is my best bet.

And that is why I made this thread to inquire about how I can extend the dropouts. So far all your suggestions are steps in the wrong direction.

Any way to lower the crank attachment point in the front? Could that front tube be cut between the steerer and the bottom bracket, a small wedge shaped section remove and then have the tube welded back together?

The way to extend dropouts is to cut them off, and weld longer ones in.

People ride bents all over the place w/o idler problems. Just sayin'

Yeah, it would take all of 30-45 minutes to replace the dropouts with ones that work. Add 15-20 minutes if I have to custom-cut them from billet plate. A minimal investment of time to finish a project that's taken hundreds of hours.

No they ride all over in denial of their idler problems. But like I said I'd rather not get into it because it's going to start a **** fight and distract from the topic at hand.

Did you consider why it took hundreds of hours to begin with? If you want something done right you have to do it yourself. The idiots at the LBS couldn't even supply me with an appropriate gear cable.

Add the time it takes to learn how to weld and custom cut the dropouts and then tell me it's an hour job.

BTW here's a pic of the entire bike w/ custom rear sprocket and 36 hole hubs laced to 24 hole rims:
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Did you try Terracycle Idlers? Thats ahs got to be a lower cost solution than to custom build hweels and a fram if all you are trying to do is get a quieter better performing chain management.

I wonder if there in an eccentric bottom bracket that would fit that frame and it if would move your crankset low enough to make this work?

That, sir, is an excellent idea. But I doubt I'd get enough play from an EBB intended for my normal BB shell.

Cheap? get a length of plastic tube to run the chain thru, it will drag thru that rather than the frame ,
Torch time..!
more realistically get a frame builder to change the dropout

they may need to make a new one cut from steel plate.

It will , one hopes include the needed location to put the torque transfer washer to make the rear wheel IG hub work..

its a short job for a well equipped machine shop,
but If you are trying to do it with hacksaws and a hand drill it definitely will take a long time ..

You may have hit a Cul de Sac ,
, different hub with a smaller cog may clear where the 25t on a Sturmey 8 speed won't.

a hub with more internal reduction gears can use a smaller external cog, S-A 8 speed has No reduction gears

This thread is going places.

Or you could revert to using a SRam dual drive Hybrid hub as the frame seems intended for as derailleur drivetrain.

It's a Nexus 8 hub, not a SA. Also the small chainring is for clearance, as is the custom 13T rear sprocket.

This was all planned out very carefully, but for some reason when I put it all together it didn't fit.

clarification accepted My computer won't enlarge Attachments so I had to guess..

FWIW 13T cogs are common my Brommy folder came with one

in 3 spline type Sturmey Archer AW have made that a defacto standard for 3 speeds

Brompton in my AW came with one and sram for brompton uses a 3/32 thick version ..

Back to the drawing board.. best laid plans of mice and Men .. and so forth

Or as G.A. Custer may have said , "where did all these Indians come from?"

Kludge Retrofit doesn't seem to work it seems , now you have a fork in the path forward.

or backtrack.. what drivetrain did it last have that worked.. ?

Well, idlers and mid drives have been the go to solutions to chain routing problems on recumbents for years. Perhaps mounting a mid drive is another solution worthy of consideration.
Consider that extending the dropouts downward will change the headtube angle and trail, possibly impacting negatively on the handling. (Twitchy enough on a SWB in my experience.)

I don't know if they even make a EBB to fit regular English threaded shells.

Your option of trying to bolt on plates at the dropouts is not going to work. It would change the spacing between the dropouts just as you suspect. And there's no commercial parts built to do what you think you want because there is no way to add what you need in a manner that would be strong enough. For the same reason I've never seen any custom made bolt on fixes for such a thing either. So you're back to welding at one end or the other or going with an idler or other tensioning scheme to allow achieving the correct chain tension.

You're also reading Danno's post wrongly. He's not suggesting that YOU learn to cut and weld to do the one hour job. He's suggesting that you pay a frame guy or other good welder to cut and weld the fix on for you. For THEM it would be a hour or so job and you just give them the money.

I don't see any way out of your situation other than welding at one end or the other. And if you set up a sliding fitment sort of deal at the rear so that it is adjustable it'll also require that your cantilever posts or brake fitting point be adjustable as well to match the movable wheel.

So better to make your adjustment at the front and then just match the adjustment with your sliding seat. For that it seems like you'd have two options.

One is to replace your current English threaded fixed shell with a single speed eccentric assembly.

The other fix would be to cut away your present English shell along with a short stub about 1 inch long of the main frame tube and add in a sliding fit length adjusting tube to the BB shell and stub part. For this you'd need to find a length of tubing that is a "seat post like" sliding fit in the main tube and remaining stub of the BB shell. Have this brazed or welded into the stub on the BB shell piece and drill a seat tube like hole and cut in the main tube. Clamp it in place and you've got an adjustable length frame. Set up the chain and then re-set your seat to make up for the 1/2 inch or so of adjustment and you're good. If you make the adjustment tube long enough you can even alter the chain length to allow for playing with different reaches between the BB and handlebars to really work in a custom fit.

Even so I'm not sure a chain run that long is wise without SOME sort of idler to help support it in the middle. But I guess time will tell if you mod the frame to allow the wheel to fit.

They do make an EBB to fit a threaded frame, see link. Although it doesn't buy you much wiggle room, and it's only for 2 piece cranks at the moment.

https://www.forwardcomponents.blogspot.com/

Sturmey does offer a hub that would be a clever mid drive . it has a sprocket attached to the spoke flange.
then there are 2 more gear ranges..
But the rear dropout is still a short vertical , have to add something for the torque washer to grab onto.. maybe there is a reaction arm to get that function.. then the dropout slot does not have to have that secondary function.
Ig Hubs rotate backwards in there in some ratio combinations and the drive torque has to be backed up, somewhere..

The only problem with the chain routing is that this particular frame is poorly designed. There are other frames available which solve it with slightly different dropouts.

The dropout extension is meant to be a temporary solution to see if the elimination of idlers/middrives/etc justifies me continuing this project and springing for a new frame. I find idlerless chain drives on uprights have a considerably better feel, but I can't be completely sure with a recumbent until I try it and it seems I'm close enough now to try before I buy.