I have a nice long HT (278mm!) and a North-Road style handlebar on this build, so plenty of room for a front rack that can be attached to the frame rather than to the fork.
I gather from YouTube influencers that this is more stable than putting it on the fork. The use-case does include mild dog-packing. Also it would be fun to give it a try.
The natural thing to do would be to braze some bosses onto the HT basically at either end, put the rack at the bottom, and have some struts going down to it. But they would get in the way. Really you want just a big flat area to put a box on.
So Iām thinking maybe three sets of bosses: one at the top, but with the struts from that going more or less straight down, then one pair level with the actual rack, and another maybe a couple of inches below that for some support from underneath (to stop the whole thing flexing downwards).
How do people usually tackle this kind of thing? Iāve got some 10x1mm stainless tube to make the actual rack out of.
Check electric cargo bikes with small wheels, lots of brands like Specy (for example) have HT mounted racks that you can take inspiration from (or buy the rack and then weld your own mounts).
Brompton also has a HT mounted rack system that they sell, you may want to check that out as well.
For the āmore stable than a fork rackā I am not sure how that could be but maybe I need to weld one and try
If you want to test the idea before modifying anything, I can confirm these will do the job without leaving a mark. As long as the part ID is right on or a little under the headtube OD, itāll be solid. Around 1mm under might be as far as Iād go. The u-bolt will splay out a little, but it just takes a little squeeze to get the ends back in line. Not pretty but totally functional to feel out the dynamics before doing something permanent.
I once used a pair at 35mm ID on a 36mm OD headtube to stick a Tern ātransporteurā rack to a Soma Buena Vista. I mean, if youāre going to put a rack where it wasnāt intended, why not go all the way? I can also confirm this made the frame feel a little noodly with a significant load. If that was going to be a permanent arrangement Iād want to brace back to the top or down tube.
So, donāt overlook torsional stresses. Any load on such a cantilevered rack will put an inertial twisting load on the head tube when the bike turns or shifts left or right. Maybe think about leaving an option open to brace to a top or down tube if it turns out to be an issue.
Do you have a picture of the bike in question? I will say that any way you can take weight off the fork will be good! But I donāt think attaching to the headtube alone will allow for much cargo beyond what a good front rack will take. Because of the lateral forces like others have said but also because how high the weight is above the front wheel. Would be keen to see ya attachment method and hear what you think of the handling if you go ahead with it!
Another idea is a cargo fork that allows for a smaller wheel and bracing back to the frame. Saw the below design a few years back and always thought it looked super solid! Designer was Apriko bikes and they did a crowd finding thing but it never reached the target. They were trying to sell them for 1,000ā¬ which is pretty much the same price as a dedicated cargo frameset of similar design. But for the home builder/fabricator it makes more sense!
Thanks for all the suggestions! I do now have a gameplan after messing around with some tubes. Iāve made the basic rack, and thereās plenty of room to give it some sort of ājowlsā at the sides: curved tubes that start at the back, and drop down about 3" before coming up to meet the front of the rack. That should give me the bracing against bending when you put a box on there that it needs. Theyāre far enough to the sides that you can swing the front wheel all the way round without it hitting it. Will send a picture when itās more finished.
Then I think I want the usual sort of U-shaped hoop at the back (to stop things bashing into the HT) and a couple of mounts to screw that onto threaded bosses I will braze to the frame.
So I just need to make sure the brake hoses and things can all move nicely.
This is the bike (I lashed it up with masking tape before painting just to check it rides OK and to work out where to braze on cable tie guides and things-- my first time building an e-bike and something with an internal hub gear).
The weight is nice and far back on this bike-- 460mm chainstay, 70 degree seat angle, and very high stack. So I think it can take a bit of weight on the front. Not sure how much the proposed dog weighs but heās pretty easy to pick up so I donāt think more than a few kg.
On the cycle trucks that Iāve made I user 1.75ā OD tubing that was pierced by the bottom of the head tube and went forward for the rack to attach to. This is effective and strong ā I was worried that it could be bouncy like a diving board but that was never an issue with loads up to 100lbs.
My mass produced Benno cargo bike has a fixed porteur/basket rack that is secured using 4 m8 bolts. They go into ~15mm tubes, one high and in front of the headtube and one low and behind. This works well for loads of up to 20lbs or a bit more.
