Recumbent Honda 90

[Michael Moore]

Peter, the GP singles were not very big bikes (about the size of a 250 Ninja), with the final versions being about 210 pounds. Besides, aero bodywork on a bike is usually there to streamline the rider, not the bike, unless of course you are riding something like a Boss Hog. The Guzzi photos are to give people an idea of what a wind tunnel-developed dustbin looks like.

Note the Guzzi fairing sides are much more rounded, which is supposed to help in cross-winds. At the Isle of Man Vic Willoughby tested a Guzzi single and then Bob McIntyre's DIY dustbin on a Norton and said the latter's "high flat fairing" was much more bothered by cross-winds.

I'd be interested in seeing the riding position too, especially since it is a street bike and rider comfort is a bigger factor than on a racer.

cheers,
Michael

[PeterS]

Originally Posted by Michael Moore

Peter, the GP singles were not very big bikes (about the size of a 250 Ninja), with the final versions being about 210 pounds. Besides, aero bodywork on a bike is usually there to streamline the rider, not the bike, unless of course you are riding something like a Boss Hog. The Guzzi photos are to give people an idea of what a wind tunnel-developed dustbin looks like.

Note the Guzzi fairing sides are much more rounded, which is supposed to help in cross-winds. At the Isle of Man Vic Willoughby tested a Guzzi single and then Bob McIntyre's DIY dustbin on a Norton and said the latter's "high flat fairing" was much more bothered by cross-winds.

I'd be interested in seeing the riding position too, especially since it is a street bike and rider comfort is a bigger factor than on a racer.

cheers,
Michael

I don't suppose you have photos in your files of those 2 different dustbin s Michael ? A comparison could be educational.

[Michael Moore]

From Vic's book "Exotic Motorcycles":



From the left: Bill Lomas (Guzzi works rider and multi-world champion), Bob McIntyre, Fergus Anderson (Guzzi rider and team manager), Vic in riding gear. 350cc Norton on the left (49) and 72 is the 350 Guzzi.

cheers,
Michael

[PeterS]

Thank you very much Michael, something definitive !! There is so much theory and supposition here that a photo of examples is great .

Just bringing forward a photo of Ironsides' dustbin to compare with the Guzzi version and it does look fairly flat on the upper sides but those cooling scoops must decrease lift if at the expense of drag.

[PeterS]

Originally Posted by Michael Moore

If you look in this directory on my website

Index of /graphics/MotoGuzzi

you'll find a number of photos of the Guzzi GP dust bin fairings that were developed in Guzzi's wind tunnel.

The fairing use on this Honda is an aftermarket item designed to appeal to the cafe racers of the period (late 50s early 60s) and could probably be improved a fair amount. NACA ducts instead of those air scoops would be a good start. The fairings on the Guzzi flat singles didn't need scoops like that:



cheers,
Michael

Michael, thank you for access to that photo file . There are lots very helpful photos there !

[Michael Moore]

Peter, there are also a lot of photos of the NSU Hammocks in this directory:

Index of /graphics/NSU

The Guzzi GP singles are my most favorite race bike. Ing. Carcano honed every single part on them to a keen edge. They weren't the most powerful but they were often the fastest bikes on the track -- good handling, good aeros, good brakes, light weight, etc.

cheers,
Michael

[bschloop]

For your tail you should consider a compound curve matching the streamlining template as closely as possible. This way you can get a full boattail with greatly reduced length. My bike is only 8'6" long with space for two.

[Ironside]

Ironside . Do you have a finished rear fairing shape in mind ?

It’s unlikely that a fully enclosed rear fairing will ever happen. A ‘helmet fairing’ is planned, similar to this :-



without the tail fin.

I understand that streamlining at the rear is equally important, but I’m prepared to sacrifice some fuel for the sake of practicality. Spring is here and some serious touring is planned, the project will evolve as time goes on, and will be a running test bed for various ideas.

A 500 mile round trip next weekend will give me real life performance and economy data which will be used as a baseline for any subsequent mods. I've been asked why I don't use my other bikes, it's because this is my favourite ride and if I have to explain, you won't understand.

One idea I’m keen to try, is a removable side skirt to fill the gap between the fairing and panniers. This will probably be a ‘Dacron’ type material held on with strips of Velcro.

Ironside, would you have a photo of yourself on the bike with the fairing fitted ?

Not a particularly good photo, but the only one I can find at the moment.
I'm about 5ft 10, and the seating position was specifically tailored for me, and is very comfortable.

since it is a street bike and rider comfort is a bigger factor than on a racer.

A larger person could be accomodated quite easily by altering the seating and footrest position.



In reply to the comments regarding the air scoops, the fairing arrived like that, and without any evidence with regards engine cooling, I thought it best to leave it as it was, 'if it ain't broke, don't fix it'.

I believe the air scoops have some advantages :-

1. They equalise the pressure behind the fairing and so prevent buffeting.
2. They may help improve the air flow between the fairing and panniers.
(I accidentally noticed this while messing about with a steam cleaner, incidentally much easier than smoke testing!)
3. They will keep me cool during heat waves.

Thanks for all the interest and comments, I will update the thread as and when I have anything interesting to say.

Ironside.

[PeterS]

Thanks for the update Ironside, all your inputs have been very helpful and I look forward to more . Thanks for the photo of you on the bike too, quite amazing , the ff position really reduces your overall height !

Have a good trip !

[PeterS]

Originally Posted by Ironside

PeterS,

The only reference I could find regarding the Cd of dustbin fairings suggested it would be around .44. Using this figure, together with the known bhp, frontal area, weight and performance, seems to agree quite closely with the calculator.

Don't be afraid to make you own fairing, it's not rocket science. I found a photo of the one that I made but never used. Basic shape made out of chickenwire, then covered with fibreglass, there are plenty of instructions on the web. It wasn't as lumpy as it looks in the photo, the plan was to smooth it out with body filler.



Get yourself a donor and make a start, it doesn't have to be finished in weekend. In the worse case scenario you can put it back to standard and sell it on. Take a look at Craig Vetter's build, Chapter 47 (I think), there's a photo of David Hyatt with his recumbent Honda passport.

Ironside

Hi Pete,

I missed your suggestion . That is really quite remarkable but I think our rego boys would disapprove however it gives a great idea of the potential of lowering the seating position..... a lot !