Recent progress on Gurty has been incremental.
After finally getting the shipping sorted out, my whee-bang! showed up.
I’ve eyeballed it in relation to the frame – packaging will be tight, but do-able.
My throttle bodies and secondary injectors showed up – packaging for them in the available space will also be tight, but do-able.
The shippers didn’t put the foil tape on either of these items.
I did that to keep cosmic debris out of the delicate bits.
Once bitten, twice shy.
The main frame down-tube is finished to my satisfaction – it looks simple, but took a little bit of getting right.
The main swingarm is… well, it’s not exactly done, but I’m satisfied that the design in my head can actually exist in the so-called real world.
It’s not a hundred percent perfect, but it meets my original use-case requirements of 300 millimetres of wheel travel with minimal variation on chain tension.
It also has adjustability, because it’s still required.
I could probably get it better, but I’ve tried literally hundreds of different configurations on my test mule, and this is about the best I’ve been able to achieve.
Why 300 mil?
Now it’s just a case of making it in steel, and running it past my tame engineer for his critique and blessing.
Once he’s happy, I’ll re-make it in black steel tube using a jig.
Now I know most of the dimensions, I just have to make sure the orientation is right and hold it steady while I tack and weld it together.
Hell, it was like gambling. I was only this nervous in casinos, but after this
site I got calmer. I recommend watching it!
This will be my hold-point – if I think I have enough time, I’ll re-make the final version in a much lighter and stronger material.
If not, I’ll happily run the tube frame for the TT trip – it will be a great way to get some field testing under my belt.
Either way, the engineer can then inspect and certify the final version so I can get a unique frame number issued and get Gurty registered.
The next tricky part is to get the rear suspension design right – I’ve just ordered two cheap shocks to use in the mock-up.
I’m striving for a progressive action based on a structure which is as light and strong as it can be, while still being useable.
Design is one component of that strategy, material is the other.
Once I get the design right, we can play with materials.
While I’m still fascinated by carbon fiber, I’ve gone away from using it.
It strikes me as something that takes a lot of practice to get right – time which I don’t really have for this job.
It also strikes me as something that you really need to be set up for – I don’t have the space or the tooling just now.
So, I’ll be sticking with metals I can cut, shape, and weld – which pretty much means aluminium or titanium for this application.
Aluminium makes more sense from a cost perspective, but money is a great measure of scarcity and a shitty measure of value.
While every project is subject to budgetary constraints, I’m striving to make a statement beyond the decrepit reach of capital.
So, I’m leaning more towards titanium for the final construction, but am well aware that this means more complexity in terms of fabrication.
I’ve been schooling myself in this regard, and, as far as I can tell, it comes down to three things: precise joint fitment, extremely hygienic preparation of the pieces to be welded, and thorough shielding of the weld pool and heat affected zone.
The process I’m describing here is intended to address the first point.
The other two I will tool up for, and address through practice.