I am back from BG Bruce, and catching up.
Anyone who frequents the front engine dragster pages on Facebook should know my opinions of the Cen-Pen/Worm frames by now. Yes they work (to a degree) and are a starting point for someone who has no experience with front engine dragsters but I have some major issues with various aspects of the frames. They are overly heavy (for no reason except for the fact the Worm seems to have a lot of .095 wall tubing in stock). Heavy does not necessarily mean stronger.
There are various engineering issues. For example the cross member that the steering box mounts to is attached to the frame with bolts through the tube--no bushings, just a hole drilled through the tube. All that stops this from being REALLY dangerous is the fact that the tube is .095 wall.
Where the two halves slip together Worm is plugging 1.25 tubing into 1.5 x .095 wall so there is more slop than I would call acceptable. For the uninitiated the norm is to step in 1/8" increments with .058 wall. Do the math and you will see how sloppy the Worm cars are at that point. If the inner tube is not rosetted to the outer (not normally required) I would be worried about fatigue at the point where the step down is welded.
The torsion bar attachment, if not dangerous, is very "clunky" with much more mass than required. Likewise the pedal package.
The one that my customer brought to me had the rear end so far forward relative to the back of the cockpit that the driver needed to slide his butt way forward to get his legs to hang over the rear axle housing, leaving the lower part of his back arched and unsupported.
The motor mount tabs are about 5" froward of what is nominally the motor mount upright so the mid plate does not act as a firewall and having the motor plate in the middle of an unsupported section of tubing is again poor engineering practice. Once again the .095 tubing is all that lets him get away with it.
The entire car is designed to be simple and quick to build (from Worm's end) as the cockpit diagonals are notched to fit the uprights only rather than in the corner of the bay intersecting the main rails as well. Some builders have been known to do this to promote chassis flexibility but with all 1.5 x .095 tubing that is not happening here. The front of the chassis is the same, rather than notch the rails to bring the overall height down to just over the torsion bar diameter (which is the traditional way to do it) Worm adds his rings and doubler plates to make it quick for him to put together.
The chassis is very shallow top to bottom which can put the steering cross member too close to the transmission in some applications. It also can make it necessary to pull the cross member to pull the transmission.
I might understand if the first cars were like this and later ones showed some improvement but they are all the same with the same issues and John claims to have built 150 of them.
One of the other talking points on Facebook was the cost of the cars but Worm's cars are not really much cheaper than most of those built by more respected builders. The fact that you can buy a car in stages is a plus but if you use his spread sheet and add all the options to get to the same stage as a Neil and Parks base car there really is not a substantial difference in the bottom line. Everyone has to start out somewhere but every builder that I respect continually works hard to improve their product but I do not see that happening with the Cen-Pen cars.
Roo
