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Knee tray construction.

Posted: Wed Jan 29, 2014 11:02 am
by voodooracer
Hello everyone. New here, but a longtime admirer of sidecars. Have decided on the sidecar driver's position for a 3-wheel drag strip exhibition vehicle and have questions I hope you'll help with.
How much of the driver's weight is supported by the knee trays and how much by the seat? After spending a lot of time searching the net, I've not come across many pics of these rigs w/o bodywork or w/o rider to get a clear view of what's going on here. I have gone over the 2013 SRA rules and see no specific guidelines either.
I've been involved w/ dragbike racing since the late '70s and have built and piloted my own machines w/ reasonable success and had a lot of fun.
If someone here would like to take the time to either pm me here, drop me an email or hope beyond hope, engage in a brief phone conversation, it would be sincerely appreciated. I've more questions, of course, but not so many that would take up a huge block of time by telephone. Real old fashioned, I know, what can I say.
Vehicle specifics are as follow: 2F/1R config. RWD, engine behind driver in frt of rear wheel, handlebar steering, hand and foot brake controls. The low and compact driver position used in sidecar racing is exactly what I need for this machine.
Sorry 'bout the long post, just wanted to give as much info as possible.
Thanks in advance for your consideration.
Keith LeBlanc
Beech Island SC

Posted: Wed Jan 29, 2014 12:47 pm
by Kyler
This is an interesting question. I'd guess that about 50% of my body weight is on my knees. In the case of a drag bike, I would think the ratio would be much higher since you have heavy acceleration forces to deal with.

If you can get a hold of Tony Foale, he may be able to help. Tony is a long time racing motorcycle designer and has designed some sidecars. He's a very friendly guy. He hangs out on the MC-CHASSIS-DESIGN Mailing List ( The list has some very talented engineers on it and they are always very helpful.

Posted: Wed Jan 29, 2014 1:13 pm
by voodooracer
Thanks, Kyler. Have read a good deal of his work. The master. Any way you could be kind enough to send pics to my e-mail of your setup? Or share some pics you may have or point me in the direction of some on the net? Really interested in materials and construction and mounting, relationship of tray to footpegs. A rigid butt-stop takes the brunt of acceleration forces, but on sit-up bikes and to a lesser degree the lay-down style still have a good deal of body weight on the seat. And I know body movement side-to-side is essential for vehicle control. You guys spend waaaay more time in the saddle than I will. Just trying to start a little ways up the design and construction ladder from PVC pipe troughs w/ foam packing peanuts glued inside rung.
Gunna do the "assume the position and take measurements" routine fairly soon and not wanting to re-invent the wheel. Thanks. I am PMing my contact info.

Posted: Wed Jan 29, 2014 2:36 pm
by Kyler
you should also go over to "The Place" ( for questions and pictures. Those guys are the no-shit experts and always seem willing to help. Their for-sale forum usually has pictures of naked bikes.

Posted: Wed Jan 29, 2014 2:39 pm
by bfd
My butt doesn't touch on the modern bike at all. On the vintage rig it only brushes when I'm trying to tuck down for a long straight.
I would think for drag racing you'd want to have as much room to move around for weight distribution and changing steering so you'd never touch either


Posted: Wed Jan 29, 2014 3:00 pm
by voodooracer
Thanks so much for the replies! I feel like you bfd, just control unwanted rear weight shift of my body and not have to pull myself fwd with the handlebars, we are talking full power, drag-slick induced wheelie bar controlled launches here, not back tire up in smoke stuff.
I'll hit up that site kyler, thanks again.
Keith LeBlanc

Posted: Wed Jan 29, 2014 5:13 pm
by ChrisWells
A bit more info on modern F1 and F2 rigs. Our "kneeler trays" tend to support the lower leg from the knee to just ahead of the ankle. The foot controls hang in space behind that (with no actual foot peg/board/stop). Most of us normal size guys don't really put any weight on the bodywork between the kneeler trays (tiny individuals may). I would think you will want to ensure the "back" of the seating area makes positive contact with your hind quarters and maybe consider molding a bit of a custom wrap around and over pocket to keep your but firmly planted inside the bike during a hard launch. Happy fiddling. Please post pictures of finished bike at rest and in action. :-)

Posted: Wed Jan 29, 2014 5:37 pm
by Kyler
ChrisWells wrote:Most of us normal size guys don't really put any weight on the bodywork between the kneeler trays (tiny individuals may).
:lol: :P :roll:

kneeler trays

Posted: Wed Jan 29, 2014 5:59 pm
by voodooracer
Thanks, Chris! Are they padded? Or textured sort of to grip the leather? Do they lie parallel to the ground or angle up from knee toward ankle for toe to ground clearance? Am I making you crazy with all the questions. Now you see how much I don't know. Ya'll live in this world that I have only got a quick glance into as it flashed by at a high rate of speed, and to tell you the truth, that goomer hangin off it draggin his shoulder on the ground kinda distracted me.
Thanks for taking the time to reply and educate me, it's really appreciated. And yes, I'll be sure to post some construction and action, even non-action pics when we have them.
Keith LeBlanc

Re: kneeler trays

Posted: Thu Jan 30, 2014 5:45 pm
by ChrisWells
voodooracer wrote:Are they padded?
Depends on your tolerance for pain and/or how much padding there is already in side your leathers. :wink:
voodooracer wrote:Or textured sort of to grip the leather? Do they lie parallel to the ground or angle up from knee toward ankle for toe to ground clearance?

Most are probably parallel or angled slightly down at the front (often with some extra padding on the rear lip for those of us with long feet). Often lined with closed cell foam which is fairly grippy. However no strict rules around any of this.



Posted: Thu Jan 30, 2014 6:45 pm
by voodooracer
Thanks, Chris, that's of great help.

Posted: Sat Feb 01, 2014 7:03 am
by Peter Essaff
our weight is as low as possible, so the fronts are lower and our toes do drag.My old Kawasaki is well padded and you sit higher than a newer outfit will allow. The Honda 600 has no padding and a bigger air box I rest my chests on. Usefull during braking we use to control body shift with. As roadracers we shift (lean)into a turn as much a we can, and place your weight as low a possible on the knees.

Both outfits the seat and knee trays are one part and slip onto pins for location and support.

I might think you need to help steer with foot pegs on a drag bike, but maybe not on a sidecar. If you use foot pags you might not need or want fronts on the knee trays.

Like Chris said, send pics.


Posted: Sat Feb 01, 2014 8:51 am
by voodooracer
Thanks, Peter. Vehicle is just in my mind's eye at this stage, so no pics available just yet. The driver position is the single biggest deviation from the norm for me, so trying to wrap my head around how you all interface with the sidecars. You all have been very helpful and I thank you for sharing. Any pics you may have and are willing to share, especially those from a bird's eye view showing the seat/knee tray/handlebar relationship would be invaluable to me.
Since there is no engine w/airbox under me should I create a chest rest? Never realized this was part of the equation. Am publishing my e-mail address and ph# here for anyone's benefit that would like to help. Thanks again so very much. I would also love to see an outfit in person and am willing to travel a reasonable amount if any of you are not too distant from the Augusta GA area. The chance to be close up and personal with one of these fascinating machines I have only seen pictures of would be a delight.

Keith LeBlanc
Beech Island SC

Posted: Sat Feb 01, 2014 4:58 pm
by ChrisWells
Hi Keith,

The closest any sidecars are likely to get to you is the Barber Vintage Festival in October. Several of us are hoping to make the trip this year.

Hope to see you there.


Posted: Tue Feb 11, 2014 6:14 pm
by Bryan R
Hi Keith,

This sounds like a cool project, I've been watching this thread and thought I'd also throw in my two cents. Chris and Pete have given good direction with the kneeler, I've found that on my F2 most of my weight is on my lower legs with the seat primarily behind me to brace against under acceleration and the front of the kneeler locking me in under braking. We don't have pegs although I have found that the upper pivot for the brake pedal ( right side) does line up with my heel and works as a foot peg when needed. Something I wanted to mention is that on a rig like ours, wheelies don't work out as good as on a bike. While I've been away from the road courses for a few years, I have been to the drag strip numerous times with the sidecar and have found launching to be the big challenge. With my daughter Shelby on the back I had to learn to slide the clutch out carefully or risk lighting the rear tire through 3rd gear if I got too aggressive. One outting I recruited my nephew to put his 210lbs of ballast over the rear tire thinking the extra traction would offset the 100lbs penalty over Shelby. It turns out that physics taught me about vehicle dynamics really quickly as the rig picked up the front tire and then headed left, right toward the christmas tree. It seems that the rig really wants to be steered and once the front tire was relieved of duty, the chair wheel took over. If I understand the configuration you're planning, 1rear 2 front wheels, ala CanAm Spyder but down low, you probably want lots of front suspension travel - drag car style with 90/10 shocks to let the weight transfer without lifting the fronts off the asphalt so you can still steer it. I'm also curious if you plan on a bike sllick out back or a car style drag slick. If you plan on a full drag slick, don't under estimate the strength of your rear axle. With my little 8" roadrace Hoosier I managed to crimp and bend a stock-style tubular axle as the sprocket really shock-loads the axle on the left side when there is lots of traction and the clutch drops. If you're going out for fun with exhibition runs, a smoke show will probably be easier & safer to run that a wheel stander, and everyone loves a half track burnout! Good luck and let us know how it's progressing.