rtciv

Hello. This is a follow-on from this thread:

https://www.bikeforums.net/showthread.php?609201

Basically, I'm dealing with a pashley trike with electric assist in the front wheel, but that wheel won't stay in the dropouts no matter what.

I need to keep the existing steering tube, since no other one is long enough.
My options are basically to either construct some kind of retaining structure to work with the existing forks, or to splice some new forks onto the old steering tube.

Here are the old forks (blue) and some BMX ones that were suggested as possible donors for the bottom part and their dropouts. In that pic, I would use the parts on the arrow side of the line, from each dropout, welding them together.













And the original forks in situ:

https://img651.imageshack.us/img651/2...f7246small.jpg


Now, I reckon the new silver forks are quite poorly suited to this job, really. The dropouts aren't particularly deep, for starters, and there might just be the same problem in the end.

So I'm thinking that fabricating something to hold the axles on, in the old dropouts, might be a better idea. I can cut sheet metal, and weld, but drilling metal isn't possible at the moment. I suppose I could manage it somehow, though.

Something like this:

https://www.bikeforums.net/showthread...1#post10153204


Does anyone have any comments or ideas at this stage?
I know I haven't covered every detail, so do ask for specifics or more info if you need it.

Thanks a lot

garage sale GT

The axle mostly needs to be restrained from twisting. What you have there is a lot like a coaster brake bike without a torque arm.

File out a heavy steel tab for each side which closely conforms to the flats on the axle, and have it attach to the fork like a coaster brake reaction arm.

I believe that what is happening is the flats cam themselves out of the dropout by twisting.

I like the Burkhardt tabs but feel it would be good enough to attach them to the fork legs with a strap and let the axle nut handle everything but the twist.

BTW if you did splice two forks together I think you'd be much better off building up the steer tube of the chrome fork and leaving the crown uncut and unwelded.

zzyzx_xyzzy

yeah, you need a reaction arm like on coaster brake hubs. The dropout on the BMX forks won't resist camming out any better than what you have. (though it might clamp better).

Better to extend the steertube on the BMX fork than to chop both forks apart at their most highly stressed locations.

bigvegan

That original fork is bent to hell, and doesn't look safe to ride, ESPECIALLY with a motor assist.

If I were you, I'd start by finding a fresh fork of the correct length and width to use with the motor assist, that would fit the Pashley headtube (maybe with a new headset), and use that, instead of cobbling together something dubious.

Why not contact Pashley and see what they recommend?

https://www.pashley.co.uk/

Pashley Cycles
Stratford-upon-Avon
Warwickshire
CV37 9NL
England
Tel : (+44) 01789 292 263
Fax : (+44) 01789 414 201
Email : hello@pashley.co.uk

BCRider

There's a big issue about why cutting and welding so you can use the chromed fork is not a good idea. Notice how the fork legs on the original Pashley fork angles forward? Note how the chromed fork has a lot less angle? If you use the chrome forks without taking this big change in rake offset into account then you will alter the steering geometry. And that is typically a bad thing.

Note how the Pashley fork is just the tubing squeezed together? That scares me. It doesn't speak well for the quality of the fork or the rest of the bike. But I guess that it is what it is.

A good alternative would be to cut away the sqeezed in portion and cut away a slot in the ends and get some front fork dropouts from a frame parts building supplier and braze the new dropouts into place. These would allow you to stick with the original fork but at the same time get yourself some far more tough and solid dropouts for the fork.

rtciv

Thanks for the replies. You're right, I should see what Pashley have to say.

In the mean time, I'll try making a reaction arm kind of thing. So I would have a flat that lies against the outside face of the dropout (with a hole in it to accomodate the axle), and then 4 or 5 inches of an arm protruding upwards and clamping onto the forks?
Could I clamp it with a jubilee clip/hose clamp, do you think?

jccaclimber

While the blue fork looks very abused (do you like your face and teeth?), you might try drilling a small hole above each dropout for the tabs on the washers to go through. That will mimic the fork setup it seems that wheel was originally designed for. The lock on rotation, even with that short arm should keep things in place. Bear in mind however that you will be removing material from an already weak structure. While I have chopped forks and swapped steer tubes on projects, it isn't something I recommend.

jccaclimber

^^Yes, a metal hose clamp is a valid way of attaching the end of a reaction arm to a frame tube.

d_D

Look at the thickness of the dropouts in the second picture. No way dropouts that thick are crimped tubing. Plus Pashley tend to produce heavy, durable and expensive products. Extreamly unlikley they would use crimped dropouts anywhere let alone a trike.

I've never seen a hub that tries to rotate the axle in the dropout that just relied on a slotted axle to prevent rotation. I suspect any off the shelf dropouts will suffer the same fate as the originals.
Perhaps you could adapt some rear dropouts and use the anti-rotation washers from an internally geared hub.
https://www.sheldonbrown.com/gloss_an...#anti-rotation

jccaclimber

I disagree. The way the tubing flares out as it becomes a dropout points to stamped, and I've seen stamped dropouts that thick.

I've seen the Nuvinci hub run with just a slotted axle and the washers. I do agree however that it seems a bit odd.