Oct 26

Oct 26, 2004

Camber and suspension watts tests

I did 4 watts test runs today and had some interesting results. Here they are in table form with a previous TCR1 watts test as a comparison:

All speeds shown are for 150 watts input power

Track Weight Camber Suspension Temp Speed
Previous test 33" 30 lbs 0 no 15 C 30.1 kph
Test #1 40" 35 lbs 0 no 4 C 28.2 kph
Test #2 40" 35 lbs slight yes 4 C 28.9 kph
Test #3 40" 35 lbs 10 degrees no 4 C 28.1 kph
Test #4 40" 35 lbs 18 degrees no 4 C 25.5 kph

The first question that comes to mind is why is the 0 camber, 0 suspension speed lower than the previous test. Well, the temperature was lower today by about 10 degrees. I did some calculations with John Tetz's power calculator and 10 degrees difference in temperature could be worth about 1 kph at 150 watts - way more than I thought. So to normalize the previous test speed, it would equal 29 kph - still 1 kph off. The weight of this suspension/camber rig is about 5 lbs, but according to the calculator, 5 additional pounds would slow me down by less than 1/10 of a kph, so that can't account for the slower speed. I imagine the slower speed is due to the increased drag due to the wider wheel track and all the gear for the suspension contraption - quite bulky and probably the reason for the 1 kph difference. A 33" track probably drafts better behind the rider than a 40" track which puts the wheels way out there. This is proof that paying attention to aerodynamics are incredibly important!

The second question that immediately comes to mind is "why is speed of the slightly cambered, suspended version HIGHER than the speed of the non cambered, non suspended version?". I haven't a clue aside from possibly wind effects or calibration errors which are both possible. Another reason could be that the height of the slightly cambered / suspended version was slightly LOWER due to the camber - this could have resulted in a very slight aerodynamic advantage.

It looks like suspension does not cost anything as far as watts input power goes, but camber definitely does! As I increased the camber from 0 to 18 degrees, average speed dropped from 29 kph to 25 kph.

The suspension really made for one sweet ride man! Very soft and in fact some areas of rumble strips couldn't even be felt! The bumpier strips created only a slight vibration and NO weird bump steer thing over the rumble strips!! Previously on the version of TCR1 that had a stiffening horizontal brace placed between the two rear wheel flanges, riding over these rumble strips on a cambered road while moving fast created a scary floating on ice feeling. That was totally gone with the suspension.

The other thing I noticed was as the camber increased, the rear of the trike dropped lower and lower - a total of 1 1/8" from full upright to 18 degree camber as measured from the bottom of the seat. There should have been an aerodynamic advantage to this drop but if there was, the added camber more than sucked up that aero advantage. I did like the feeling of being a bit lower - the trike felt very stable and the peddling position and seat position felt really good. The reason I am higher than the camber tests put me is to see safely over the top of the fairing. Because the fairing will cover everything, my seat height will make no difference to the speed of the faired bike.

To summarize, adding camber would not be a good idea unless it was very slight - but I am even skeptical about that. Adding suspension for a cross country TCR1 does make sense because it seems to remove bump steer and strange vibrations from rumble strips. I would probably NOT do the swing arm suspension for a final working concept because I think it's way overkill. Perhaps all that is required is a Pantour suspension hub, (who now have a TRIKE hub!!) or individual shocks built into each wheel flange - something that won't add much of an aerodynamic penalty and something that would allow each wheel to absorb bumps with VERTICAL movement rather than a cambered movement.

Another good idea for the cross country TCR1 would be to work at getting the center of gravity a few inches LOWER because that seemed to make a bit of a difference in how the trike felt in turns. I am sure some of the extra stability I felt today was due to the added weight across the rear axle also. The way to do that without effecting my hip angle (which I am happy with) is to raise the rear wheel flanges a couple of inches. That results in lowering the rear of the frame and increasing the trail by a inch or so - which also felt good.


I am going to put cross country TCR1 to bed for a while and focus on a track version for an HPV speed record attempt. That will be more like the original TCR1 - 33" track, no suspension, no camber, and one brake on the front wheel. I'll call it TCR2 for now.

The test fairing should be ready tomorrow!!! I'll be very busy building mounts for the fairing, figuring out how to open the top up, how to get in and out, visibility, room inside, and how I plan to handle the steering in it - which I may revert to simpler brake lever steering. Since I'll be going around a track, I don't require very much of a turn radius and I think I can get away with a couple of inches of cable movement from a brake lever. Sometimes when I'm cruising down the highway I maintain my heading by pressing down slightly on the exposed part of the steering cables as they run into the sheaves under my seat. This slight push on the cable is usually enough to make bearing adjustments - and only a little more would be good enough for a turn at higher speeds.


Good news from Kevin Thompson today on provincial permits to do the cross Canada record. He writes: "Here's the response from BC which is quite favour able. Alberta is no problem. Saskatchewan and Manitoba are just a phone calls. So we're okay until Ontario which is what I'm still waiting to hear about."


Also, I'd like to officially welcome a new member to our family - Helens new Kestrel Airfoil Pro - a fully carbon 15.5 pound beauty!


TCR2 (track) 2Do LIST:

1. Make a platform for the wind trainer (mini-rollers)
2. Add front caliper brake
3. Mount first fairing and all the work required with that
4. Make CF front wheel fairing
5. Make CF rear wheel discs
6. Redesign steering bar to above waist (possibly brake lever steering for record bike???)
7. Adjustable seat height


TCR1 (cross country) 2Do LIST:

1 Add front derailleur
2 Run road, roll-over and watts tests for new suspension system
3 Worm gear steer prototype (Waiting for final design and parts list from Ben)

TOTAL distance on TCR1
704 km


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