Thread: Electrathon - A Different Kind of "Hotrod"

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I will be interested to see what your battery experimentation yields. If it saves money in the long run it could be a boost to the sport.

What kind of sprocket adapter does shiftev make? If they make the ones that hold the standard 5-hole bicycle sprocket ring, you don't want it. Bicycle chains are junk for Electrathon; they stretch like elastic and frequently come off the wheel sprocket. I used bicycle chain and sprockets on our team's first Electrathon car (Blue Sky Aerocoupe) back in 2003 & '04. It did OK in its first two races, both on smooth ovals. In its third event it kept jumping off. I didn't realize that it had stretched to the point that the chain no longer matched the pitch of the teeth on the sprockets!

If you Personal Message me I can give you the e-mail address for Rodney Schreck in Miami. He makes the sprocket hubs (pictured below) that I use and sells them for $99. He uses an ordinary rear wheel sprocket cassette and adds a sprocket adapter that holds a regular 6-hole go-kart sprocket. Rodney bolts the adapter plate to the sprocket on the cassette. When I get them I weld the two pieces together and then discard the bolts, but that's just a matter of preference to eliminate the possibility of the bolts ever working loose.

I hope the battery experiments yield something useful. As you mentioned earlier, if I run Li-ion batteries, I will probably be in my own class. Rather than keep secrets for a competitive advantage I might as well take the time to make the results public as others can learn from my mistakes

Yes, what you picture is exactly what I need. Professional cyclist often use a new chain for each race. Bicycles can get by with such light chains because their rear triangles are very ridge and cyclists lean into the corners so any flex happens in the same plane as the chain.

I am speculating that one of the reasons your frame designs are so reliable (and successful) is your use of curved tubes in the rear triangle and front wheel support. These curves provide a bit a suspension so your vehicles flex rather than bounce or break.

As a result, I am going with a go-kart chain. The product shifttev sells is https://shiftev.com/index.php/compon...ory_id/25.html

Actually, if you study the picture of my latest bare frame design (below) you may notice that almost everything except the front axle is triangulated. The frames I build are very stiff. Flex is desirable in a go-kart frame to provide traction and handling. It is unnecessary in a 3-wheel vehicle where weight transfer is absolute. The EMT conduit I use to build frames will fatigue and crack if allowed to flex. The rear fork in my frame is triangulated vertically on both sides as viewed from the side and rear and horizontally at the bottom as viewed from below. I don't want any movement in the rear wheel as that causes thrown chains.

The front axle main tube is arched in the center so the ends descend toward the spindle. It is very rigid and the bottom supports are curved mostly for appearance, but will allow the front axle to bend if serious impact occurs. (It's happened more than once!) I don't triangulate my front axles because if the car is involved in a crash I want the axle to bend without transferring damage to the frame.

Nice,

The current frame design looks like it has gone through several generations of refinement

Yes, it has been improved continuously from use and experience. Since the white car build in the first half of this thread I have changed the front hoop of the roll cage slightly and added the extra triangulation to the bottom of the rear fork. Otherwise, the design is dimensionally the same.

The change to the roll cage was strictly for driver comfort; the white car's front roll cage hoop put pressure on my upper arms when cornering and became uncomfortable after a while. I simply raised and deepened the bends to get the vertical portion farther forward.

The extra braces were added to the bottom of the rear fork after I had a problem with frame flex! After I finished the white car and raced it twice I built the black car (which I still own). In my first practice session with the black car I kept hearing chain binding noise in every corner. About halfway through the 3rd lap the chain broke! The rear fork was twisting badly in every corner. The problem never occurred with the white car (different rear forks?), but since it showed up in the black car I have added the extra bracing to all subsequent chassis.

I do enjoy looking in from time to time,as Jim said reg bike chain can go bad n dose. I used pro high $ bike race chain n had no probs,but it did cost about 5X as much,very lite car with only 1HP,but as I was also using 6speed set up,the derailer with extra MB spring held very well. In a car with higher lbs n HP may of failed too.

Finally started the frame build... and promptly threw out 80% of what we talked about. It didn’t seem like I had a good enough feel for what I was doing to convert my paper plan into tubing. I am do this frame by eyeball and feel.

The most satisfying part of the week as been building all the jigs to hold things in place before welding.

For this build, I am intentionally leaving things flexible and weak. I wouldn’t want to race it But, hope to gain a better feel for where and why thing bend and break by tooling around the parking lot

The first week of December when I started my frame build was a wake up call. I had gotten pretty good welding flat stock on a bench. Even the short stubs of tubing I was using for practice were good-enough. However when it came time to weld the frame, everything fell apart. I had not prepared for welding weird angles from weird positions.

It took a couple of days to pick my self esteem off the ground and figure out what to do next. I thought about cutting the frame up and reassembling it with each tube an inch of two small just for the practice But the time spent cutting and fitting the tube would be too great compared to the practice spent welding.

Yesterday, I took a piece of 16 gauge sheet metal and cut it into 2 inch by 2 inch triangles. I used these triangles as gussets at each joint. Each gusset required 4 welds of about 2 inches each…. from many different positions.

The key for me is fit prior to welding. It I go slow enough to get good fusion, I tend to blow though even tiny gaps. It is probably a matter of practice For now, it means a lot of time on the grinder getting things to fit as closely as possible.

On Saturday the 6th we raced at Middleton High School in Tampa. This year, because of other events taking place at the school, we were moved to a different parking lot than the one we used in past years. The course was a simple oval which is fine, but this was the roughest course we have ever encountered! Most of the track was OK, but there was a patched area in the asphalt (it was turn two in the first race, turn 3 in the second race) that created multiple bone-jarring bumps on every lap. I tried every possible line through that turn and there was just no good way. The first race was run in a clockwise direction (all right turns) and when it was over my left elbow and shoulder were sore from the beating they took against the inside of my car. The good news is I finished second with my son right behind me in third. Rodney Schreck won by 2 laps driving the car I built for him, so that means Robinson built cars finished 1-2-3.

The second race ran the opposite direction (all left turns). The bumpy section was now giving my right arm all the torture. I was in pain and I simply was not having fun. On the 43rd lap, as I was exiting turn 2, the car suddenly danced sideways and I knew what that meant. I slowed, limped around the rough turn, and ducked into the pits with a flat rear tire. I was actually thankful that I had an excuse to quit! Changing the rear tire would take upward of 15 minutes and the laps lost would be insurmountable, so I just climbed out to watch the rest of the race... Late in the race Rodney coasted into the pits; the key had come out of his motor sprocket and it was slipping. I grabbed the appropriate hex wrench and tightened the set screw into the key slot on his motor and got him going, but he lost a total of 3 laps in the pits. My son won the second race by about 6 seconds over the Electrocutioners car from Orlando and Rodney finished third, 3 laps down.

At the end of the day my son won the event! Rodney was second, 1 lap down and I was credited with fifth (6 cars in Open division). The nearest finishing high school car was about 20 laps back! The school kids just can't understand how a bunch of fat old guys keep outrunning them. It's all about consistency.

Now to repair and prepare the cars. The beating from that rough course cracked the Lexan covering on the nose of the 94 car around several of the rivets. The 13 car has some broken spokes on both front wheels. I haven't checked it yet, but I suspect both cars will require front-end alignment. The bottom line - if they run that same course next year I'm staying home!

David,
I assume you are using a MIG welder or a flux-core wire welder. Either is good. Trying to run a continuous weld bead on thin material is a challenge for the most experienced of welders. About the time you get a good weld puddle, the metal blows through and you have a gaping hole to fill. Try using a series of overlapping tack welds. That's the most successful way to weld this thin stuff. When you start the weld, watch the puddle. As soon as it gets nice and round (this happens very quickly), stop. When the puddle loses its glow, start again. Do this over and over until you have completed the weld. It will seem like slow going, but actually saves time over having to constantly repair blow-holes. When done right the finished weld looks like a bunch of overlapping circles or "stack of coins". I've been doing this for years and not all of my welds are pretty, but I'll take strength over looks any day.

Thanks for race report,fun read,High Five for top 3 cars in frist race n super your son's job.

Thanks for posting the race highlights, Jim. I always enjoy your posts!

X's 3, thanks for the updates and congrats on the successes!

Congratulation on your good showing. Is this the start of a dynasty for Robinson Racing.

Last week I chopped up V1 (version 1) in order to start fresh on V2 for the new year. I thought I would share a couple of lessons that might be useful for builders without a lot of experience.

1. Build a decent platform. This platform will be the base for all measurements and fastening jigs. A two foot by eight foot sheet of ½ inch plywood on two sawhorses was not enough. For this iteration I fastened the sheet of plywood to eight foot 2X4s running beneath the plywood like floor joists. This provides a nice solid platform which does not sag that is still light enough to move out of the way if the space is needed.

2. Screw a eight foot measuring tape directly to the middle of the plywood platform. The edge of the tape provides a reliable mid-line and the tape provide a constant frame of reference for measurements along the length.

3. Prepare a bunch of layout blocks. In order to hold things in place for welding you will need fixtures to hold the tubing in place. Rather than scrounge up a suitable piece of scrap while you are thinking about the joint, it is handy to have a bunch of pre-drilled blocks on hand. You will already have enough on your mind when doing the lay out.

4. Set a tolerance. While working is it hard to know what is good enough. Experience must help a lot, but until I have that experience I decide that everything must be within 1/16 of an inch when fitting most parts. Steering and driveline must be a good deal more exact This seems reasonable without being too exacting.

5. Set a margin of error of joint fits. After a bit of experimentation I found that having no more than .035 of an inch gap on joints makes for pretty decent welds for someone of my experience level. Anything bigger and I tended to blowholes

I look forward to hearing more about your season!

Thanks for all the compliments, everyone. My son's win eased some of the pain I was feeling after the event, but I was still sore for two days after! I'm probably getting too old for this.., but it's just so darn much fun! Next race is January 17 at Wharton High School. I don't particularly like the track layout, but at least it's tolerably smooth.

David - If you look back at the beginning of this thread, I used a 2' x 8' piece of 1/2" plywood to make my "frame jig" platform. At the time I had it clamped to two work tables in the school shop. That kept it flat and level, but I later put 1" x 4" (on edge) framing under its perimeter and then added "wings" on either side to locate the side pods. I also built a fixture to hold the rear fork in place instead of using the plumb bob and measuring tape. Another fixture holds the kingpin bosses at the correct angle for welding and others hold the rear hoop and roll bars at their correct heights. I cut a stack of 2" x 4" blocks from 3/4" plywood to use for holding the tubing in place on the platform (plus I clamp the bottom rails down) and attached them with drywall screws so they can be moved if necessary. I'm still using the jig and all the fixtures. It's showing a little wear after having built 9 frames, but is still flat and accurate. I bend, cut, fit, and tack all the pieces together. Then I weld everything that I can reach easily. After that I take the frame off the jig and roll it over and over to weld all the otherwise difficult areas.

I just have a center line drawn on my jig, but attaching the measuring tape along the center is a good idea. Speaking of measuring tapes, if you need to measure around corners or a piece that is already bent, get a fabric tape measure from the sewing department at Walmart or a fabric store. I've kept a couple in my shop for years.