Wheel Spats Part I

My idea for the spats is to try and make a single oversize mould, and then make four mouldings that can be cut down and stuck on to Quattro. I don't want to spend too much time on them, I just need something rough and ready that I can test on the track.

I have tried to compare Quattro with and without spats in Solidworks CFD and there seems to be little difference in the drag figures. This is actually quite encouraging from the point of view of adding the spats as I have not modelled in the gaps around the wheels, there is no rolling road and the wheels are not rotating.

If they work well, I want to incorporate them in my Quattro re-design. My idea is to have the major portion of all four spats as part of the bottom moulding. There would then be a lower removable section that can be taken off to change a wheel or access other components. By doing this, I am hoping that I can get rid of the removable panels underneath; they are heavy, the thin edges are prone to chipping and they make the mouldings rather complicated.

The quick and dirty mould is made from two MDF female formers with a thin sheet of plastic expanded and clamped into position. The formers are simple aero shapes, the top one 900mm x 180mm and the bottom one is 300mm x 60mm and they are 225mm apart. This will make oversize, conical and symmetrical parts that I can trim to fit around all four wheels.

Wheel Spat Mould

The aerofoil section I have used is simply an elliptical nose and a radius tail section. The radii are tangential to the ellipse and where they meet at the tail, they have an included angle of 32deg.

Aero Section

The main body and head fairing of Quattro are designed using similar “homemade” sections. I experimented with more sophisticated NACA profile but couldn’t measure any significant difference in CFD.

 

First Moulding as Template

I moulded a couple of wheel spats that I am using as templates but then ran out of cloth, so my moulding man is making me six. Four are for Quattro and two for experimenting on Beano.

I am locking my suspension at the moment for the spat test, I have pushed the front wheels out a bit further to match the rear wheels and should end up with a ground clearance of about 125mm, with a horizontal bottom. There are three 5mm section O-rings fitted on each of the suspension struts to give a little cushioning.

The reason I am locking the suspension is so that I can bring the spats right down to the ground to get maximum benefit. If there are any benefits that is, hopefully we can get to Reading Velodrome at the end of this week or early next week to give them a try…..

Castle Combe April 2012

Quattro I and Quattro II

The second race of the year was at Castle Combe motor racing circuit. This has generally been an early season event and as it is a wide race track, it is normally run as a single two hour race.

It is a simple triangular track, three main comers and three straights with kinks in each, plus the addition of chicanes in two of the straights. The lap distance is 1.85miles (3k) with a slight downhill along the main straight, when going clockwise.

The weather forecasters predicted the worst day of the year so far and they were not wrong. There was continuous heavy rain and very strong winds. When Steve and I arrived, there was a small group of competitors huddled on the sheltered side of one of the buildings. Unfortunately we don’t bring enough people to the race track to justify them opening the cafe. When we joined the group, there was a general discussion going on about whether to abandon the meeting or to shorten the race.

A number of people then volunteered to brave the conditions and do a test lap. Ian Fardoe’s video can be seen here. http://www.youtube.com/watch?v=xCZe4d2q6gM

This was the first time I had seen Quattro II in a working condition. I had initially made enough parts for two and sold an almost complete pile of bits to Graham Sparey-Taylor, for him to build up. The main thing he was short of was a head fairing; I had chopped the other one down for the ROAM trip. He made his own, rather lovely, carbon fibre version from the original mould, as seen on the right of the picture. Graham has also taken out my original moulded pedal box and replaced it with a tubular steel bottom bracket support. This was because there was insufficient adjustment in the leg length and he also wants to add an electric assist at the front.

The conclusion from the lap testers was inconclusive, with some saying it was too dangerous and others wanting to go for it. I took Quattro out for a lap and was pleasantly surprised how well it handled the conditions. In the end it was decided that there would be a half hour mass start race for anyone who wanted to compete. Steve was keen to have a go in Beano but I quashed his enthusiasm as I didn’t want the job of mending it if he did crash.

We lined up on the track and started the race, not realising that Ian Perry and Ian Fardoe were still out on a warm-up lap. For the first time in many years, I found myself leading a race. As the wind was predominantly blowing up the hill, I found my pace was much more even than normal at this circuit. My forward vision was OK as I can look through the vent hole at the bottom of the screen, trying to find the apex of the corners was a little more difficult because of the raindrops on the screen. Inside Quattro, I could tell the conditions outside were bad, but I was amazed how little I was being blown about. Before the race, I was worried about the effect the side winds would have on my rear steering, but if anything, I think if may be compensating for the side gusts.

I maintained a high speed but not flat out for the majority of the race and kept checking the mirrors as best I could. I was consistently passing other riders but had no idea where the two Ians were. Unfortunately for me, the first time I saw Ian Perry in my mirrors, was on the last corner when he came sprinting past. It was a fair result however as he had to make up a lot of ground on me due to his late start. I am also happy because his machine, Wobbly Bob is a cut down version of my Bubble and Squeak.

Ian Perry and Wobbly Bob at Monza 2011

Wobbly Bob 2012

These are the provisional results for the day.

Ian P.                8 laps. 36.13.   m/o
Miles K.            8 laps. 36.16.   m/o
Ian F.                8 laps. 38.11.   m/o
Andy F.             7 laps. 40.55.   u/p/o
Guss N.            7 laps. 41.15.   st/sp/u/p/o
Geoff B.            6 laps. 38.20.   Sp/u/p/o
John L.              6 laps. 38.41.   m/u/p/o
Yoshamora.      5 laps   36.27.   st/sp/u/p/o
Sam K.              5 laps. 36.51.   m/u/p/o
Graham st.        5 laps. 42.31.   m/o
Martin D.           4 laps. 38.59.   st/sp/u/p/o

Clare k.             1 lap.    5.51      l/st/sp/u/p/o
Barney h.          1 lap.    6.13.     u/p/o

If I am not mistaken, the points from this race added to my Hillingdon points puts me first in the championship! It won’t last unfortunately.

My average speed was about 24.5mph (40kph), which I am quite pleased with considering the conditions. Graham was not quite as lucky in Quattro II as his pedal fell off halfway through the race. He can’t blame the designer for that one though!

My Quattro was un-changed from the tests we did on the velodrome in Reading. I did leave the extended tail off as its benefits were dubious and I spent some time finely tuning the tracking the day before the race.

Our next event is on 20^th May on a velodrome in Scunthorpe and I am hoping to add some spats (wheel fairings) before then.

CAD Image Quattro with Spats

Testing at Reading Velodrome

Beano at Reading Velodrome

Before the season opener at Hillingdon, Steve and I went to the velodrome at Reading to check all was OK with the Beano and Quattro. This was my first outing with the Scorcher tyres fitted, so I was hoping for good things. This was also an opportunity to test some modifications that Lee Wakefield had kindly done on Steve’s Beano.

Well, the Steve / Beano combination was as swift as ever and everything was working well. In Quattro, I was able to lap at about 26-27mph for a few laps, which was a little disappointing. The new tyres didn’t seem to be giving me the benefits I was expecting.

Steve in Quattro at Reading Velodrome

After the first race at Hillingdon and the discovery that I had tracking issues with Quattro, we decided to go back to Reading and try again, this time with the wheels all pointing in the same direction!

Using the laser spirit levels, I had tracked all four wheels to as near parallel as I could manage. I know you should only change one thing at a time, but I had also taken 32mm out of the height of the head fairing.

On the second trip to Reading, I was at least 10% faster with speeds of 29/30mph for a few laps, compared with 26/27mph last time. Slash was able to lap at about 32.5mph but he was over stretching for the pedals despite some seat padding.

No Add-On Tail

We both seemed to be slightly (1/2mph) faster without the add-on tail which was a surprise.

Without any way of measuring the power input at the moment, these tests are not very scientific, but as long as I am going a bit faster, I am happy.
I imagine the overall improvement is mainly due to the better tracking. It did seem to roll a lot better when free-wheeling. I have done a fair amount of training and the chopped lid must help a little, but I am sure the tracking is the key.
There was a hot plastic sort of smell again, which I noticed last time we came to Reading. It only seemed to happen on one of the banked bends but needs investigating.

Nose Too Low?

Watching Steve going round was interesting; having lifted up the rear of Quattro 1/2deg, for better forward vision, the nose now looks too low. I might try and jack up the front to get the bottom horizontal again.

2012 Season Opener

The first race of the 2012 season was at the Hillingdon Cycle Circuit on the 1^st April. For those of you not familiar with the circuit, it is 0.96 mile, fast, smooth and very popular with laid back cyclists. It does have a long and fast hairpin bend which can be taken more or less flat out, but it does scrub off speed for us multi-track riders.

For the race, I fitted Greenspeed Scorchers and my new Ackermann compensation, with four wheel steering, equal front and back. My road tests of the four wheel equal steering were not perfect, as the handling was poor on bumpy surfaces at speed. However I found that I had forgotten to tighten some of the lower wishbone mounting screws. So I thought I would give it a try.

Front Ackermann

Rear Ackermann

Rear Close-up

I also made some aerodynamic changes to Quattro with an extended tail and a more relaxed tail angle, reduced from about 20deg to 16deg. Both additions were a bit of a bodge but I thought they may prove a point.

Relaxed Tail Angle

Add On Tail

The race went OK and I managed a 24.6mph (39.6kph) average speed in the hour race. Steve won in the Beano as usual with an average speed of 34.7mph (55.9kph). There were comments after the race that I was making a lot of tyre noise, which I put down to the large volume and high pressure in my Scorchers. Back at work the next day, I was looking over Quattro when I noticed a strange texture on the front tyres.

Front Tyre Texture

Checking the tracking on the bench with Quattro on its side seemed to suggest that it was OK; this was using the method I had always employed, with two steel tubes, resting on the rims. To double check all was OK, I decided to buy a couple of laser spirit levels.

Laser Spirit Level

Resting On Wheel

The lasers told a different story. With Quattro on the ground, both front and rear wheels were about 0.37deg each toe out, 0.74deg for the pair. Rider weight and applying power seemed to have little effect, which keeps things simple.

Quattro Gearing

The original Quattro gearing was a triple chainring and an extended Capreo block with a custom derailleur. Although this worked OK, I didn’t trust it to take me all the way across the USA.

Custom Derailleur

Tensioner

I decided to fit a standard short cage 105 derailleur, with an extra custom tensioner to take up the slack.

The gearing for ROAM was 72T, 60T & 45T chainrings and a standard Capreo 9 speed block, 9T, 10T, 11T, 13T, 15T, 17T, 20T, 23T & 26T.

Front Wheel Drive

This gives a top gear of 72x16/9 = 128” (10.3m) and a bottom gear of 45x16/26 = 27.7” (2.23m), which is a range of 462% but I was badly over-geared on hills over 10%.

Sliding Gears

What I would like to try is a single chainring and a straight chain line. The extended block slides left and right on some kind of spline and the tensioner is fixed.

Aiming for a gear range of 500% based on the Capreo block, there are three relatively simple options.

Gear Number	Capreo 9 Speed Block	Shimano HG61 Block	Custom Sprockets	Result
1	9			9
2	10			10
3	11			11
4	13	12		12
5	15	14		14
6	17	16		16
7	20	18		18
8	23	21		21
9	26	24		24
10		28		28
11		32		32
12		36		36
13			40	40
14			45	45

This gives some nice close ratios for racing but I discard most of the expensive Capreo Block.

Alternatively

Gear Number	Capreo 9 Speed Block	Custom Sprockets	Result
1	9		9
2	10		10
3	11		11
4	13		13
5	15		15
6	17		17
7	20		20
8	23		23
9	26		26
10		30	30
11		34	34
12		39	39
13		45	45

This gives slightly wider ratios but is physically narrower and nothing is discarded.

Alternatively

Gear Number	Capreo 9 Speed Block	Shimano Sprocket	Custom Sprockets	Result
1	9			9
2	10			10
3	11			11
4		12		12
5	13			13
6	15			15
7	17			17
8	20			20
9	23			23
10	26			26
11			30	30
12			34	34
13			39	39
14			45	45

This gives nice close ratios for racing and as many gears as a Rohloff Hub!

They all give a top gear of 72x16/9 = 128” (10.3m) and a bottom gear of 72x16/45 = 25.6” (2.06m).

For any future tours I would probably reduce the chainring to say 65T.

Giving a top gear of 65x16/9 = 115.6” (9.31m) and a bottom gear of 65x16/45 = 23.1” (1.86m).

9T Selected

 

45T Selected

It was easier to make an MDF mock-up of the tensioner shape and position, than to try and draw it on the computer.