Blog 2 - Bump Course Design
by Al HalfakerIt was my intention to build a small easy little bump then a larger bump and finally a bump that would get your attention. The bumps had to be spaced far enough a part so the rider and suspension's reaction to driving over the bump could be observed and analyzed before the driver and suspension reacted to the second and third bump.
The bumps were built in my garage and hauled out to my 10 acre flat field. I measured out 60 feet between bumps and figured that would be plenty of separation between the bumps. I anticipated testing would take place over a month or so. I needed to shoot video on a sunny day for the videos to look good. As you know in Minnesota this year so far we have had lots of cloudy days with many snow days. I had to plow out the course very wide and long to allow plenty of room for the truck to build up enough speed in the field to video the snowmobiles on the course and still slow down at the end of the field. Second the course goes from south to north and the prevailing wind blows from the west or northwest. If I plowed the course to narrow it would drift in on me and the video truck would end up to close the snowmobile being videoed. I plowed off the snow 90 feet wide and 300 feet long in preparation for anchoring the three bumps shown below 60 feet apart on December 1st. 2010. It is now February 2nd 2011. The course is now about 225 feet wide. It is still plenty wide for videoing.
I had to think long and hard to come up with a bump track that could be affective at slower speeds to show how suspensions perform over smaller and larger bumps. I decided to build bumps out of ¾" layers of plywood that 450 pound to 600 pound snowmobiles will not destroy. The best design I could come up with would come to a peak and be sturdy enough for a snowmobile to bounce over at up to 30 mph without damaging the bumps or the snowmobile. The bumps are built out of ¾" treated plywood bolted together for the largest jump and ¾" plywood screwed together for the smaller bumps.
Once the bumps were built I had to come up with a method of keeping the bumps from moving. Three foot mobile home tie down anchors with ¾” rod screwed into the ground at slotted ends of the three jumps worked great. See pictures above. I wanted the three bumps to be 60’ apart so individual bump performance would not effect suspension performance over the next bump.
The full course
This winter I have been keeping the bumps clean of snow and the field plowed about 90 feet wide and 300 feet long around the test track bumps. All snowmobiles and their suspensions will ride over the exact same bump with no snow build up on the bumps that would distort the test results.
If you would like to test your snowmobile on the bump test track and or try my RX-1 M-20 airwave suspension on the track, just give TeamFast a call.
The bump track is designed to safely handle any snowmobile riding up to 30 mph over the bumps. The test snowmobiles in feature videos in blog four are either running 20 mph or 30 mph. You will see a definite difference in the suspension performance of all factory suspensions tested versus the M-20 and M-10 airwave suspensions.
My wife Patti, ready to take some video
The videos were taken out the passenger window of my Chevrolet truck at either 20 mph or 30 mph while driving parallel to the bump test track.
Next up in this series of blog entries is a description of the difference between OEM suspensions (see Blog 3 - Independent vs. coupled suspensions) and then finally, the videos demonstrating the difference (see Blog 4 - Suspension demonstration videos).
02-09-2011
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