Finishing the Ram-air System
My available time over the last two week has been taken up with producing some more carbon fibre components. I am pleased with the progress achieved in terms of the process itself and learnt a tremendous amount since the beginning. After reading more than a fair share, I've started using pre-preg carbon fibre as opposed to wet-lay and vacuum bagging. The resultant parts are considerably better quality and the process is actually easier since you don’t have to bother with wet epoxy and its related clean-up. Although, it does require storing the pre-preg material in a freezer (good thing there’s a full size freezer chest in the garage), and a well controlled curing oven, which we built ourselves. After some research, I decided to try Sprint 85 as the pre-preg material which is made by Gurit. And, the early results are very encouraging. It is a two layer carbon fibre material with a layer of epoxy in between. This makes it easy to lay-up dry and it then takes 10 hours in the curing oven at 80 deg. Celsius with carefully controlled temperature ramps. Vacuum bagging is still required, of course.
In any event, the first semi-structural piece I've attempted is the front air intake conveyor. It feeds fresh air straight through the headstock into the air-box. It also serves as a front fairing mount and as a mount for the AIM Sports dash. It is, in effect, a front subframe and ram-air tube in one. Total weight is 350 grams. Last year’s version made from 7020 aluminium weighed 1.6 kg and had no air channel.
These pictures show the detail of the air conveyor/front subframe mounted to the frame, and with the fairing in place.
In the side view, you can see the carbon conveyor extending fore and aft of the headstock. The large yellow foam piece is the male mould for the air-box (to be made next)
The yellow part visible at the end of the conveyor (inside) is the air-box. It’s hard to imagine a more direct path for ram-air. I don’t have a huge expectation of any additional horsepower from the effects of ram-air. This subject is much studied, yet the results seem to vary widely. Our air-box will have a pressure sensor and the air-box pressure will be connected to the AIM dash logger. So, at least we’ll have some data if we decide to develop this further. Based on my limited knowledge on this subject, it seems that one thing you don’t want is large peaks of negative pressure, i.e. an air-box vacuum.
A somewhat gratuitous picture of the reasonable close-up from the right side.
The next few pictures show the new tank made from aluminium and made by the same fabricator who did all the metal work on the rest of the bike, including frame, swinging arm, subframe. Of course, he made me build a full-scale model in MDF first! I didn't expect to have to do any wood work in building this bike.
The large yellow 'ish foam is the male mould for the air-box. It forms part of the top of the tank in order to get as much volume as possible. At the front just behind the headstock, it has a cover that hides the ECU and a couple of other electronic boxes. That makes the electronics easily accessible without having to remove the tank and they are now well protected in case of a nasty crash.
I am really pleased with the outcome of the tank both its shape and how it works together with the air-box. All of the tank’s volume is located vertically above the gearbox. If necessary, additional volume could be added by extending it under the seat unit. As it is, it holds about 10 litres, which is plenty for club racing.
And lastly, a frontal view with the top fairing in place. You can see the v-shaped air intake that I grafted onto the fairing. This slips inside the front of the air conveyor and thereby constitutes the front fairing mount. You can also notice how well that Kawasaki 650cc twin engine “hides” inside the fairing. In frontal profile and area, it doesn’t look any different to the Honda RS250, which is of course what the goal was.