Tuesday, November 18, 2008


This is my new favorite Brooklands photo. It's from 1925, and shows two anonymous racers 'down to it' on the Member's Banking, riding low on the fast inside line. Both riders are on single cylinder machines, both are wearing boots and helmets, but the standard of protective clothing ended there; woolen jumpers and trousers were perfectly acceptable. It must have been a coldish day as both riders are wearing more than one layer of wool up top. Number 30's machine seems to have a Blackburne engine, but the make of the bike is impossible to tell.

The scale of the track is clear; it dwarfs the riders, and the patchy quality of the concrete surface is readily apparent. But the photographer's position, right on the edge of the track, really brings the viewer into the action.

1 comment:

Anonymous said...


I have just spent the last few days reading the entirety of your exceptional blog. I discovered it poking around for some ideas for a project i'm about to undertake, a full on reproduction of a 1910's-1920's motorcycle. It has (much to the detriment of my studies) fully engrossed me in the potential of such a project, narrowed my focus in terms of what style of cycle, and raised more than a few questions about the actual accomplishment of such a build.

These early engines have always intrigued me, from the inventiveness and diversity of design to the artistry in the castings. I'm a 5th year mechanical engineering student, and with the theoretical 'toolbox' i've built over the last few years, the question has arisen- what kind of performance could be attained using modern mathematical modeling and simulation within the bounds of 1920's manufacturing processes and design concepts. Taking the basic mechanical design to its fully optimized state, and also a fun exercise in backyard metallurgy and engine design.

I'm pretty convinced that i'd like to model my chassis after your Royal Enfield Works Sprinter. The lines are beautifully spartan, the construction would be inexpensive and doable with the tools i have at hand, and it provides a good test bed for the engine, which i am most interested in developing. Your blog had excellent pictures from which i can get the proportions and angles, but i would like to know the rim diameter, so i can calculate actual dimensions.

I also have a few questions about the feasibility which require someone who has actually ridden and worked with these bikes to answer. First off, i'm using internal components from a briggs and stratton sidevalve 8 horsepower engine. I'll be making my own crankshaft, cases, cylinder and head, so i will use a stroke that will give me 350cc's- as a 'junior' class replica. The briggs is already close to these dimensions. I've tuned briggs engines like this to 15+ horsepower. What power do you estimate the Enfield 2 stroke produces? What speed does this result in? Would 15 horsepower be ridiculously overpowered for this frame? I'm one of those crazy moped army people also, so i'm comfortable going 60+ mph on 2 inch tires with no suspension. With 15-20 horsepower it would be fantastic to break the ton- perhaps you have some thoughts on whether that chassis could maintain stability at those speeds.

Pending information on the size of the wheels, i was considering the use of bicycle rims, as they are readily and cheaply available. 17" moped wheels are also an option, as well as some sort of narrow dirtbike wheel, either one's drum brakes would compromise my design however. Is the construction of these old wheels essentially the same as a bicycle wheel? I would begin my search with 19-20" wheels from a heavy, older, cruiser-type bike.

I think that is about all i need to continue my design. Once i hammer out a few more design parameters, i will begin on making patterns, hopefully to have some castings in the upcoming months. I'll be doccumenting the process, and if you are interested i would be more than happy to post it to your blog when i finish. If things turn out well, I may even hang a shingle doing custom sandcast reproduction engine parts. It is very encouraging to see there is a community of enthusiasts who actively ride and maintain vintage iron, i look forward to having the financial means to partake myself.

Thank you for any assistance you can provide,

Graham Motzing