Electrathon America Forum

Date: Dec 10, 2010

spindles

Zaine Stapleton · Senior Member

I got mine at Vancouver Bolt. My car's front wheels only accept a 20 mm axle. The Guys at Centennial High School, two of their cars (#12 and #42) both have 20 mm front axles. I wanted to get the same as they had and that is what the bike shop had to work with.

mhodgertt · EA President

At Willamette High we make spindles etc. for all 20+ of our cars we build each year. We use the Tomos Moped aluminum mag wheels and they take 12-mm axle bolts. We machine the brass bushings to hold our 3/8" kingpin bolts in the kingpin tube and then have made a jig for our shop press to bend cold rolled 1/4" X 1" steel strapping into the "C" shape for the C bracket spindle. These work great for us and seem to hold up well. It would be nice to use a larger bolt like a 14-mm or larger but there are not bearings that fit our wheels and have a larger I.D. If anyone wants any diagrams, etc. of our front spindle system let me know and I can Fax it to you.
Mike Hodgert

Date: Dec 15, 2010

Zaine Stapleton wrote:

I got mine at Vancouver Bolt. My car's front wheels only accept a 20 mm axle. The Guys at Centennial High School, two of their cars (#12 and #42) both have 20 mm front axles. I wanted to get the same as they had and that is what the bike shop had to work with.

I called them and they said they didn't have spindles. Did you just buy a 20 mm bolts and fab a spindle?

meangreen · teacher / board member

I fabricate my own spindles. The trouble with 20 mm bolts is they are HEAVY! So, I use 1/2 inch grade eight bolts and then use Oilite bushings (1/2 in. I.D, 3/4 in. O.D.) from ACE Hardware. There is a complete write-up with photos in my car-build thread on Club Hotrod. Here's the link to the article:
http://www.clubhotrod.com/forums/showthread.php?t=41183
You may have to join in order to see the photos; it's free. smile

Zaine Stapleton · Senior Member

I went with a 20mm bolt so I wouldn't snap off a 12mm bolt that would cost me a race. Plus, I wanted to get something that was tough and wouldn't be a problem when driving, I'm pretty aggressive in the corners.

meangreen · teacher / board member

The ideal situation would be to put the 20mm bolts in a lathe and bore a 7/16 in. hole all the way through the center. That would lighten them about 40%. Grade 5 bolts would be strong enough and boring out the centers would not compromise appreciable strength. Unfortunately, I don't have access to a lathe...

As for breaking spindles, I am yet to see it happen. I am nearly 50 pounds over the minimum weight (just under 230) and I drive my cars very hard sometimes. I have broken spokes, collapsed wheels, hit curbs, locked wheels with other cars, bent the front suspension, and bent tie rods, but I am yet to ever break a spindle. Those grade 8 bolts are very tough. I suspect that if spindles break, either they are inferior grade material (too soft) or the metal may have been compromised by improper welding...

electrathon · administrator

At Centennial we have both half inch and 20mm spindles. We are switching things up as we replace parts. I have been at a lot of races over the years and can say I have literally seen hundreds of half inch grade 8 spindles snap. Keep in mind that I go to more than 10 races a year and have been doing this for over 10 years. We had one particularly greuling dip to cross at one race that claimed over 20 axles at a single race. Some cars broke one side, got back in and broke the other side! We have broken half inch spindles on our cars over the years too.

If you are racing on a smooth track, half inch is good. We have brutal bumps to cross (yes, we even are airborn over a few of them). Someplace we got cool footage last year at PIR from our lap counting camera as the wheel rolled over the start line, followed by the car sliding across. The bigger bolts are cheap insurance though.

Aaron

meangreen · teacher / board member

I agree, better safe than sorry. If I ever get access to a lathe I'll make up some hollow 20 mm bolts...

I still have to wonder, though, if maybe some of the teams are putting too much heat into the spindles during welding. If a grade 8 bolt is overheated it will lose its strength. The composition of the metal can revert back to its pre-heat treated (soft) condition. Also, if the part is overheated and then cooled too quickly by quenching in water, it will become brittle.

bd64 · Senior Member

4140 12mm welded and heat treated axles do not break even going over bumps and jumps and slamming curb bending wheels but they will bend.

dmorgan · Member

Best of my recollection, bolts are graded on tensile strength not shear. A grade 8, properly torqued, will hold til the cows come home. However, one put in a shear situation after being torqued(stretched) will snap just as quick as a regular Grade 5 automotive bolt. Next time you break one , take a long look at the point of fracture. The grain of the metal will show you the cause.

electrathon · administrator

dmorgan wrote:
Best of my recollection, bolts are graded on tensile strength not shear. A grade 8, properly torqued, will hold til the cows come home. However, one put in a shear situation after being torqued(stretched) will snap just as quick as a regular Grade 5 automotive bolt. Next time you break one , take a long look at the point of fracture. The grain of the metal will show you the cause.

It is rare for an axle bolt to be actually torqued. Most of the teams leave the nut just a little loose, very similar to how wheel bearings are in a car. And half inch grade 8 bolts, supported on only one end do break. Sometimes they are welded at the head, sometimes not, depending on the thickness and design of the axle.