Derby Talk is a forum for Pinewood Derby, Awana Grand Prix, Kub Kar Rally, Shape N Race Derby, Space Derby, Raingutter Regatta and other similar races where a child and an adult work together to create a race vehicle and a lot of fun and memories
I can't help but wonder if lightening up the main body would be better done with a drill? Instead of large rectangular pockets you'd end up with more of a honeycomb, which would seemingly be a stronger (or rather better use of remaining wood) than narrow strips of wood and large pockets. Said another way, all else being equal -- e.g., if you removed just as much wood with drill holes than with the scroll saw, the remaining structure would be stronger. Might be easier too.
I've considered doing that. Went as far as sketching out two patterns, using 3/8" and 1/4" sized holes, but I never got around to try cutting it out.
davidwilkie wrote:I can't help but wonder if lightening up the main body would be better done with a drill? Instead of large rectangular pockets you'd end up with more of a honeycomb, which would seemingly be a stronger (or rather better use of remaining wood) than narrow strips of wood and large pockets. Said another way, all else being equal -- e.g., if you removed just as much wood with drill holes than with the scroll saw, the remaining structure would be stronger. Might be easier too.
Using a drill to achieve an intricate honeycomb pattern that would remove enough weight to be competitive would be pretty hard to achieve, in my opinion. There's a lot of opportunity for torsion-based tear-out with a drill, that could destroy your work in the latter stages of drilling the final few holes. It might work, but for those who have a scrollsaw, the ladder design is pretty easy to do in 15-30 minutes.
If I didn't have a scrollsaw, I'd drill out a lot of holes, then chip out the remaining rough material left behind to make 1-2 large rectangular voids, then I'd laminate top and bottom with balsa or basswood sheets for added support/rigidity.
Scrollsawer wrote:There's a lot of opportunity for torsion-based tear-out with a drill, that could destroy your work in the latter stages of drilling the final few holes. Scrollsawer.
We were thinking drill the holes before cutting the body thin, so that we wouldn't have to drill the holes all the way through (which would seem to lower the risk)...and then cut the body thin on a bandsaw.
I was experimenting with my own washer wheel weights. The washers that I found that have the same OD but a smaller ID where "fender" washers. The ID is only 1/4". I was able to fit a stack of 4 inside the wheel but even with a tight wheel gap the bottom edge stuck out of the wheel and would have rubbed the rail if the car wobbled. Next time I was going to just use 2-3. From what I have read now that the big speed guys have been using wheel weights is maximizing the weight isn't the biggest factor for wheel weighting compared to the aerodynamic effect.
sporty wrote:
One washer sitting in there. hard to take a pic and not have it look like the washer is not center. I think this one turned out good.
I'd like to make a mold and make some lead ones.
I do think these washers might be a tad tight, just took a wheel and went to the local hardware store. 15 cents each.
a vender sells a double washer, I got a email out to them, the local store had a display of a double washer, one piece. but only the display and they don't carry them.
17/32, 1/x11/64. not sure the size will work, trying to get a sample to find out. my local store don't carry metric washers, I wanted to look at them too.
These here, as I said, might be a little too big, not sure. id have to build a car and find out.