2012 Update - Season 2 - Race Day 9/22/2012
I have spent the last several weeks working to get the downhill racer ready for this season.
First a recap of what worked and where we needed to improve:
1 - The brakes worked, without shudder. However, my grandson had some difficulty applying enough pressure.
2 - I fabbed the rear axle by welding a purchased stub axle onto a washer and then welding that to the end of a square tube axle. The stub axle weld (inside the square tube) failed, allowing the wheel to angle in at the top and creating drag.
3 - When coming off the starting ramp the first time, my grandson cocked the steering, leading to the bending of the spindle assembly. We were able to straighten it at the track.
4 - Ran out of time on the body - we weren't pretty enough.
5- I couldn't find the kind of seat I wanted, so made a padded bottom and back.
6 - I didn't have a way to weigh the car and we were under weight, reducing top speed.
To make the rear axle stronger, I inserted a length of 1/2" rod into a 3/4" tube and welded it in place. This assembly was inserted into the 1" axle tube on the chassis and welded into place. The rod was then threaded and polished to the correct diameter to allow installation of the wheels. In the process of doing this, I narrowed the track by 16".
The front track was narrowed by 16". The front spindles were rebuilt with heavier metal and reinforcement to make them stronger.
My son and daughter-in-law found an IKEA seat that seemed ideal for the task. The second picture shows the fabricated bracket.
First, cool project.
re: #1 (brake pedal effort) Use leverage to your (or your grandson's) advantage. Trade a bit of pedal travel distance for increased actuation force by changing/adjusting the brake pedal leverage/linkage.
re: #2 (rear axle weld failure) You stated that you are using a Lincoln Weld-Pak100 with C25 gas. That machine is a 120V input power machine with a max output power (amperage) of 100 amps. Fine machine for welding 'thin' stuff, like your 16 ga steel tube frame pieces. But that machine just doesn't have enough power to weld anything thicker than about 14 ga thick using 0.025/0.030 solid wire and C25 gas. If using FCAW wire (Lincoln NR211MP) in 0.035 diameter, those machines can go to maybe 1/4 inch thick steel at max output.
Welding thicker material than that and you end up with inadequate penetration aka inadequate fusion aka cold lap. The molten electrode wire mostly just melts on top of the thicker parent material and doesn't melt into the thicker parent material. It may look just fine, but will be weak because the steel pieces and the weld filler/electrode have not achieved the 'proper' Welding-Zen State-of-Oneness (where the steel has all melted together and fused into one homgeneous piece).
You said you took a piece of 1/2 inch diameter solid steel and put that inside a piece of 3/4 inch OD steel tube (with some 1/8 inch thick walls you end up with a 1/2 inch ID, so the rod slips into the tube just fine). Your machine can maybe melt the hollow tube, but just does not have the amperage to melt into the 1/2 inch diameter solid steel rod.
You then inserted that fabbed-up 'rod' into the 1 inch square hollow tube of the frame/axle-support. Your Weld-Pak100 may have enough power to MIG weld the 14 ga square tube, but really does not have enough ooomph to weld all that fabbed-up 3/4 OD steel 'rod'. You just piled up some steel but didn't weld it all together.
I'm all for scrounging and repurposing, but I really think it would have been a bit 'better' to just get some 3/4 inch solid steel rod and put that into your 'axle tube' instead of all the attempted weld build up using the 1/2 inch OD steel rod. Just my NSHO. A couple of plug welds through the square tube might be enough to hold the solid rod in place, or put a cross-pin or cross-bolt through the items.
re: #3 (steering spindle bent and reinforcement) See above about welding 'thicker' material with the WeldPak100. Looking at your pictures of the steering spindle reinforcement, the welds look a bit 'cold' (inadequate fusion/penetration) with the weld filler/electrode metal jsut sitting on top of the gussets/bracket/angle-iron.
Project Update 8/10/2012
The last several weeks have been spent trying to make the car prettier than last year.
After doing preliminary body work, I decided I needed to remate the body to the chassis to make sure I didn't create any undesired stresses or curves in the body work.
This is a shot showing the car after the second coat of automotive primer.
The car with two coats of Rustoleum spray can paint.
The cockpit.
Next up is to determine assembled weight and make the necessary additional weights to go in the weight box and see about some graphics.
Wow, you've got the bug now! Very neat, and I hope your grandson knows how special this is.
I feel silly telling this story, but when I was a kid all I wanted was a go-kart. Dad never had the desire to build or buy one...why, I'll never know. Finally when he was at work one day I sneaked into the garage, took a flat board, a couple rods, some old lawn spreader wheels, and set to building one. I couldn't have been more than 7 or 8?
I painted the board black with a spray can , hammered in nails and bent them over the rods to hold the axles in place, and that was as far as I got before dad caught me.
He was pi$$ed!! Tore the thing apart and never said anything more about it. All the way through junior high I drew plans of go-karts, tree houses, clubhouses...But I never tried to build another
Can't wait to see your next race!
Flames baby, flames.
