Strange fork on a Sherpa (not mine)

[mickeg]

I have never seen anything like this before.  At first glance I think it is a butchers bike with a frame mounted platform in front of the head tube.  But then realize that it is a standard frame.  A small front wheel fork on a full size bike frame, that appears to have correct geometry.  Saw this photo at this article, realized it was a Thorn.
https://bikepacking.com/plog/sounds-from-london-to-lyon-ep-1-video/

Photo without text is here, I zoomed in to see the Sherpa model name:
https://bikepacking.com/wp-content/uploads/2024/07/Sounds-from-London-to-Lyon-Episode-1_16.jpg

Looks like a 20 inch wheel, but the fork must have really long fork blades to make sure the geometry is not messed up, longer than 700c I suspect.  With the canti posts in the right place for that wheel.

Pasted this from the article:
Morris rides a Thorn Sherpa with a custom cargo fork that he built himself to allow for increased carrying capacity. It’s a bit like a DIY Omnium or just a cheaper Crust Clydesdale fork.

It looks like a triple crank with a missing outer ring, and a derailleur adjusted as if the outer ring was still there.

Interesting.

[PH]

Thanks for the link, interesting indeed, I'll have a watch of the video later.
The idea of a small wheel fork and platform isn't something new.  As well as the butcher type bikes, I've seen a few replacement forks for standard bikes offered, such as this one:
https://global.bluelug.com/crust-bikes-clydesdale-cargo-fork.html

I did consider one for deliveries, did a bit of research, it seems you don't have to exactly match the mechanical trail, there's also what is sometimes referred to as pneumatic trail and this is effected by weight.  Most Brompton (Or other small wheel bike) riders will be aware of this.  Even if they don't know a name for it, they'll know the steering is considerably tamed by adding some weight to the front.
In the end, I decided it was too costly an experiment, though I remain curious.  I have seen a delivery rider with a bodged version, basically what looks like a suspension corrected fork with a 20" front wheel and a basket somehow attached, on a standard rigid 26" wheel MTB.  I've only seen it in passing, I'd be interested to have a better look and know what it rides like.

[Danneaux]

Not so terribly unusual, George; do a Google search for "Cargo Bike Conversion Forks" [no quotes] or click on this link...
https://www.google.com/search?q=cargo+bike+conversion+forks&oq=cargo+bike+conversion+forks&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIICAEQABgWGB4yDQgCEAAYhgMYgAQYigUyDQgDEAAYhgMYgAQYigUyDQgEEAAYhgMYgAQYigUyDQgFEAAYhgMYgAQYigUyDQgGEAAYhgMYgAQYigUyCggHEAAYgAQYogQyCggIEAAYgAQYogQyCggJEAAYgAQYogTSAQgzNjA3ajBqN6gCALACAA&sourceid=chrome&ie=UTF-8

The key to making one (I did, mostly, before abandoning it as inappropriate for my needs compared to other solutions) pleasant to ride is to keep the bike's original head angle/height insofar as possible and then determine a desirable amount of trail on the finished "step" fork, all while keeping in mind the smaller wheel diameter. The desired/desirable trail is where decisions have to be made. Generally, low(er)-trail designs favor heavy front-loading, which is what these cargo forks are intended for.

In lieu of super-long fork blades, most designs use a split fork as shown in the Clydesdale design photos.

In my case I used the original fork, cut off about 2/3 of the way through and the newly shortened ends brazed to a horizontal tube. I then took another pre-built fork and sectioned it, brazing the bottom sections to the same crossmember. Rake adjustment was achieved not by bending but by the angle of the lower fork blades when brazed. I repurposed an old pair of seatstays as my lower blade-to-rack girder and that worked fine. The trouble is, the fork weighed a lot and I found a box on the relatively small platform really didn't work as well for me and the cargo I generally carry as did a pair of panniers on a front rack. If I had needed something to carry vertically stacked boxes to the post office, maybe, but for those kinds of trips I prefer one of my self-built trailers.

EDIT: Having written all that, I found a video tutorial that nicely details the basic build process...
https://www.youtube.com/watch?v=ijfmEkNPAsU

Best, Dan.

[mickeg]

Thanks Ph and Dan.  Apparently it is not as rare as I thought, but I have never seen anything like that.

There appears to be enough curve in his fork blades to make that a very short trail fork, but since I am just eyeballing that from the photo, could be in error.  But it would make sense that he wants a short trail for less flop over if he stacks the boxes up on top of his front rack.

There are bikes with 36 inch wheels, quite rare but I have seen photos.  Rim has 787mm bead diameter.  I suspect that fork would be pretty close to what you need to put that on a 26 inch or 700c frame with a 20 inch wheel, or maybe even 16 inch.  But of course you would want disc brake instead.