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jerm1386
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1#
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Rank:none
Score:260
Posts:260
From: USA 
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:23 PM)
Part 1: Background Two months before I started this project I had never done any metalworking of any kind, save for a couple small projects that could be handled with a dremel and some two-part epoxy. In the two months prior to this kart build I helped DrScope build and assemble four loaner karts: the yellow, white, and blue karts, plus the original black kart which is now Neals’s frame. DrScope and I were working from a more or less proven design which he had used before.  I didn’t have to do much thinking in those builds, just followed instructions; this was a good introduction to the tools in his shop, where parts and supplies were. Along the way I made some improvements to ‘my’ loaner, the DW1386X. I put additional camera mounts on it, gave it a different steering rod mount (Electrical conduit, lighter than steel square tube), ‘removable’ steering wheel, upgraded the front wheels, and made the steering speed slightly more to my tastes and controllability. I never intended to use this kart forever, though. Once the DW1386X was complete enough to be moderately competitive, I started working on the next generation, a new and original kart built from scratch. This would be longer, heavier, have a different driver posture, and hopefully have some sort of suspension. I had a ton of ideas and that was good, but ultimately not all of them were implemented – this time.  (the new kart turned out nothing like my drawings)
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jerm1386
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2#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:26 PM)
Part 2: Frame Work I started the frame for my new kart shortly after the April race, hoping to have it up and running in some form by the May race. I did reach that goal, but it meant cutting a few corners and not including some features that I would upgrade later. I was comfortable with this, though, as I wanted to try the kart out as I went. The frame was longer and narrower than the loaner’s. This would allow for less wind resistance both because of the narrow frame, but also because the longer frame allowed me to lay down more in the kart, sticking less area in the air stream.  The seat I chose was one of those vinyl video rockers meant for people playing video games in their living room. I flipped it so that its back was now the seat and the short 'seat' was now the back. It doesn’t have much back support but races are relatively short anyway and even without back support, the seat is comfortable. In the interests of aerodynamics, the frame was made as close to my body as possible while still allowing me to have a comfortable position in the kart. At this point I thought I would be making my own kart body out of fiberglass or sheet metal, and that the brake pedals, steering system, and suspension would be contained in a separate nose cone to be bolted onto the front square portion of the frame.  Ultimately, the brakes and steering would be contained within the forward part of the nose, pushing my body back a couple inches, subtly but significantly altering my body position. The moral of that story is always give yourself a bit more space than you think you'll need; I designed a kart to exactly fit my body and now I have a kart that is ever-so-slightly too small for me. Though I thought the frame above was complete, it turns out there were more structural elements that had to be added. The most notable was a horizontal brace from the upper frame just in front of the steering wheel to meet the roll cage. Before, the body flexed too much. After adding that brace, the frame was much more able to take abuse. I also added a triangulating element within the main side opening, for extra stiffness in case of a crash. Other members have been added and modified, but none were as important as those.  This is the frame with steering system and wheels two months after it first raced.
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jerm1386
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3#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:28 PM)
Part 3: Making Corners I decided that buying a ready-made rack setup would be too expensive and that the spindle/pitman arm ratio solution to slowing down turns could only carry me so far on homemade parts. I figured that some sort of gear reduction would be the best option, and promptly tore into a bicycle, salvaging a couple gears and the chain. DrScope suggested that maybe bike gears and chain weren't reliable enough and directed me toward one of Neal's old timing chains. This has worked beautifully as a steering reduction system and I have never had any sort of steering-related wobble at any speeds under any cornering conditions. I have had to sacrifice feedback through the steering yoke, though, I cannot feel the road through the wheel. Fortunately the kart goes where I point it and so it isn’t a problem. I have also never had to use the tension-adjustment system I put in.  I had salvaged the bike with the intent only of using the gears and chain, but the only part I used was the handlebars, at least the lower handlebar support. This portion of the bars turns out to be a good steering yoke. Since space was at a premium in the kart, I needed to have a yoke rather than a wheel. A wheel would have been placed very high to avoid my legs. Brake handlebars were added with the intent of attaching brakes to them, but that didn't happen for two months after the fact. Bike grips ensured a comfortable, non-slip yoke, and the wheel was attached to the steering linkage via quick-release to aid in cockpit entry and exit. 
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jerm1386
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4#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:31 PM)
Part 4: Getting Rolling, Iteration 1 From the get-go I knew what wheels I wanted to use: four identical pocketbike wheels from a 47cc pocketbike. Drscope managed to dig up a slightly larger version of those wheels, though, so I used the originals for the fronts and the larger ones for the rear.  The problem with that, though, was that at the time did not have time to make up new spindles for the race. So I used a pair of old spindles from the DW1386X and popped on some racing slicks mounted on azusa rims. They look pretty badass, but they're wide, sticky tires so they probably slowed me down when I used them. The tie rods were cheap thin ones that worked for this first go, but were quickly replaced. For the rears I just used a pair of harbor freight wheels on a solid one-piece axle tack-welded to an adjustable frame mount. This rear axle was adjustable because I figured I might want to vary the ride height to suit different courses: at this point I had given up hope for any sort of suspension. Technically, the front axle height was adjustable, too, but because of the steering mechanism interfering, the range of adjustment was minimal.  In my haste to get the kart rolling I forgot to solidify the axle welds and it came loose mid-race, sliding about 6-8" back and forth in its mount. It felt like a really bad fishtail or extremely quick steering setup, but I was able to keep it under control (which involved riding brake the second half of the hill). Since it was a wet race and I had a new steering system I chalked it up to that at first until I rolled the kart into position to get pulled uphill and I noticed the axle alignment was way off. 
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jerm1386
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5#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:33 PM)
Part 5: Getting Rolling, Iteration 2 After the kart showed disappointing performance in its inaugural race I decided to make some improvements. This time I had two months to build it before it was to be raced next, so I had plenty of time to work it all out. The first things that were replaced were the tie rods: the ones that had been in the kart were flimsy and barely reached the spindles. Jola's kart got a rack and pinion steering upgrade and no longer needed its old, heavy-duty tie rods so I liberated them from the parts boxes immediately. Next, the front wheels were switched out to the pocketbike wheels I had originally intended. Since the axles on the new wheels were 3/8" as opposed to 5/8", I had top build new spindles. Rather than the older-style spindles that were just a rod, a tube, and a few holes I built full wheel cages. The intent was twofold: since the axle was so thin and the kart was not as light as DW1386X (also 3/8" front axles), the cage supports the axle at both ends, ensuring it won't flex or break. Also, the wheel cage offers some protection from contact with other karts: if someone hits my wheels in a race I won't slow down.  Originally I just planned to replace the harbor freight wheels with the new larger pocketbike wheels. Once I took a look at the new wheels, though, I realized the bearings were a 12mm inner diameter, too small to fit on the 5/8" axle. So the idea for a rear wheel cage was born. As DrScope and I were planning it out, we realized it might be worth a shot to try to add rear suspension to the wheel cage. Both wheels would be directly linked: not an independent suspension, but this has advantages in simplicity. The suspension mostly serves to make the ride smoother.  a while ago I had bought some springs on eBay with the intent of making a fully suspended kart. This ended up not happening and so I had four ultra-stiff springs sitting around. I made up a couple rails with a bunch of holes (so it would be, of course, adjustable) that the spring mounting axles could go into. As it turns out I lacked foresight and only one set of holes fit while also providing acceptable ride height: other combinations could work but I'd bottom out through large bumps - not good when trying to go fast. So not only was this system heavy, but it didn't even work right! I am now in the process of making it infinitely adjustable with a lighter system, win-win in my book.
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jerm1386
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6#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:36 PM)
Part 6: when I need to stop So I was planning on build a super fast kart, I needed to know how to stop it quickly. Not like I want to apply the brakes in the middle of a race, but if there were an unforeseen obstacle, making a quick and controlled stop would be essential to performance and driver safety. Make no mistake, this kart is heavy so making a quick, controlled stop on such small wheels and a heavy frame is quite unlikely, but I'll do the best I can Iteration 1 sported a hand lever-actuated rear scrub brake that barely worked. It’s only worth mentioning because it's so vastly different from what I'm using now. I don't even have any pictures of it: it was last-minute and thankfully it worked well enough to keep me in control when my rear axle came loose. New for July were rear-wheel disk brakes. This was a poorly thought-out system, but one that did serve its purpose. All the cable guides were closed without a brake line removal slot so the brake cable had to be threaded out of the entire system to be removed, the brakes were mounted on a too-flexible piece of strap that had to be bolted down a very certain way not to rub the disks, the axle flexed causing the disk-caliper alignment to be wrong, etc.  New for august were front-wheel disk brakes. I kept the rear-wheel system, poor as it might be, because I figured the fronts would make up for it. They did, and when I made the front wheel system it turned out very well. Not as well as it could, but well enough to work and not to rub. my front wheels were perfectly silent when spinning. I finally got the chance to use the yoke-mounted brake levers.  September obviously wouldn't show any more wheels with brakes, but I did upgrade my rears. The system I had used to hold them on wasn't living up to expectations so I redesigned it. With so much space between axle supports, the axle was flexing and making the brakes rub once my weight was in the kart. I ran another support right next to the wheels, eliminating the axle flex. I then re-mounted the brakes, welding the mounts permanently to the support. This eliminated most of the adjustability, but still allowed it laterally so I figured it was all ok. 
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jerm1386
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7#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:38 PM)
Part 7: Bodybuilding I like how this kart looks like without a body on it. I like seeing just the framework, my design out there in the open. In fact, my favorite photo was taken just before the july race, but a body was definitely necessary to get the most out of the kart. Drscope had an indy car body laying around that he got off ebay. The rear spoiler had broken off during shipping and the front wings had already been ripped off, so the cockpit effectively had no back. One day in July we were working on the kart when drscope put the indy body on the kart, just for the hell of it. It turned out to be a pretty good fit, so I quickly installed some rivnuts and floorboards to hold the new body on with six bolts.  The body was not long enough, but we vowed to do up some fiberglass or sheet metal. The rear spoiler was affixed to the back suspension system even though we doubted its usefulness. 
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jerm1386
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8#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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RE:Punishing One: Build Process
(Date Posted:11/02/2009 13:42 PM)
Part 8: Upgrades Of course I had a working kart in September, so why wouldn't I want to tear it all to shreds and completely redesign certain parts of it? Because I can, because it can go faster, because it was too heavy, and because I was sick of wearing those spandex pants just to fit inside. 8.1: Body The body was doing great, but it still had big holes in the sides. The fiberglass just sort of ended about where I was sitting, leaving a hole in the side big enough my torso effectively had no side impact protection. Also, it wasn’t close to aerodynamic, thus it had to be fixed.  Rather than attempt a fiberglass body piece, we opted for bending sheet metal out of sheer simplicity. It was somewhat tricky to make a side frame that lined up with the current body, but it was not impossible. A day’s work with the shop tools gave me a very sturdy pair of impact bars on both sides on the body plus sheet metal riveted to those rails. It sits relatively flush with the fiberglass. The rear ends of these panels were bent inward slightly  8.2: Spoiler One innovation this kart has taken from racing cars is the rear spoiler. Having some true experience racing, DrScope mentioned that one time he put a cockpit-adjustable wing in one of his cars, allowing it to go through turns much quicker, helping it win races. We therefore mounted my rear spoiler on hinges and put in a control bar so that the left ‘brake’ pedal would push the spoiler up so I could use it both to brake and provide additional downforce in turns. This spoiler detached itself from the kart while traveling up to the ECC. It is doubtful I would have won if the spoiler were still on the kart. The November race was not fast enough to warrant its use, either so it remains untested in a racing situation. There are no pictures of this because it was built the day before the shootout, a very rushed day when there was no time for photography 8.3: Brakes. Having four-wheel independent-control brakes is nice, if you make use of them. I had two pedals and two levers for each of my four wheels, but I found after a while that I never used the sides independently of each other: in the race I’d only ever use both pedals or both levers in unison, so there was no great advantage in being able to trigger the left and right sides independently. While I haven’t done anything about the front brake levers, I did combine the real brake pedals into one pedal with adjustable side bias. This allowed me to use the other brake pedal as the spoiler-raising pedal. If Punishing One remains my main kart for a while, I would like to combine all brakes into one pedal, remove the hand levers, and keep the left pedal as the spoiler pedal 8.4: Suspension In order to save some weight, I removed the adjustable rear suspension and put in a new wheelcage that was immovably attached to the frame. The new wheel cage implemented a new suspension design that would actually allow adjustments to be made, adjusting the ride height that way. Whuile this saved much weight over the previous design, widened the track of the rear wheels, and shortened my kart by a couple inches, if I had to do it all again I would keep the system I had. Ever since putting on the new wheelcage my kart has had problems with bouncing all over the road. I suspect that because my old suspension had a poor hinge, the hinge acted like a damper for my springs, giving me a true shock. Now that my rear hinge is on bearings and pivots very smoothly, the springs bounce a lot more, sometimes even allowing the rear wheels to come off the ground (this is conjecture).  8.5: Cockpit This kart is just plain too small for me. Specifically, it is too narrow near my hips and too short. To remedy the narrowness, I cut apart the part of the frame that was too small and replaced it with something wider. Specifically, the vertical tubes that hold the front harness strap on were cut just above the harness mount point. I replaced them with angled tubes that connected the upper and lower planes closer to the front of the kart.   To remedy the shortness problem I compacted the steering box by about two inches. I had designed it for more range and adjustments than I was actually using, so I was able to shorten the box significantly, giving me what felt to be loads more space. The kart is much more comfortable to drive now though it’s still a bit on the short side.
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jerm1386
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9#
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Rank:none
Score:260
Posts:260
From: USA
Registered:02/12/2009
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Re:Punishing One: Build Process
(Date Posted:11/02/2009 13:42 PM)
Part 9: Futures
With the 2009 shootout behind us, the Punishing One has seen the bulk of its building and upgrading days. It is now a kart ready for anything and although continuing to upgrade is an attractive option, I'd like to start fresh again. Also, while I like the kart, I enjoy driving it, and it has been fun to build, I have no great love for it. Its design and construction were limited too much by my inexperience, cost, and parts availability and so it has turned out too far from what I had really wanted. My next kart, the Lotus 7 look-alike "Weekend Warrior" has been in planning for a couple months and will likely debut next year, reaching developmental maturity in time for the shootout, as Punishing One did. While I'd like to say what it will have, how big and heavy it will be, and how fast it will run, I hate making promises I can't keep. Building a kart is a lesson in changing your plans and going with what works rather than adhering to a predetermined set of drawings. Regardless what I have in store for it right now, the only thing I can guarantee is that it won’t turn out how I imagine it right now. So all I can say for now is that it's in the works.
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