| Author | Message | ||
     Greg_e |
Looking for sources of knowledge. I'd like to research design and fabrication to build myself an adult sized, 125cc, 12 inch wheeled, road racing bike. Needs to be a little bigger than my KAYO. Target tracks are Kart tracks. Target engine is probably the single cylinder 125cc TTR125 engine or similar. The more cheap dirtbike parts I can incorporate, the better. But it should have at least a half fairing when I'm done. Probably welded steel tubes (round or rectangular) since I can't weld aluminum (yet). Looking for books, websites, people I can contact, etc. If anyone knows Mr. Buell personally and would show him this post, that would be even better. A "mini" XBxR would be just the ticket. But this is not a high dollar build, it's an out of pocket build and may take a long time between design and buying tubing and parts assemblies. Off the shelf forks and shocks, probably even cheap Asian made products like those from Fastace that are all over the monkey bike scene are the target here. I may also need to call in favors for larger parts that need to be machined, my mill is too small to make things like triple trees an easy task. Though slicing a headstock off of a cheap donor would go a long way to completion (again another reason to work in steel). If this sounds interesting, please offer whatever help you can. Knowledge is the first thing needed, designing something decent for these little wheels is a bit different and isn't just a question of shrinking a full size racebike to fit. | ||
| Greg_e |
I forgot to put in one link that I'll read through: https://www.cycleworld.com/how-to-hand-build-motor cycle-frames-skills-and-techniques | ||
| Shoggin |
You'll have to pick either 'from scratch' or 'cheap'. They are mutually exclusive to each other if you want to like the finished product. Is this just for fun? I applaud the desire to do it, but even building a bike from scratch with an existing frame isn't very cost effective.} | ||
| Greg_e |
Well, the level of race isn't up to MotoGP standards, so cost should be able to be contained. If I think I can swing whatever it is going to take, then I'll give it a go to build it. I know there is a long lines of things like jigs that will need to be made. But I was thinking about the Super7 car plans, with the right donor you can build that for around $5000 in materials and parts. A bike made from a wrecked dirtbike motor and some reasonable suspension components shouldn't cost much more than $3000 and a huge chunk of time. I wonder how a YZ80 front end would do on a paved track, might have to ask about this on another forum. Might be able to alter something like that to produce the head angles and stuff without as much custom building. Need the same knowledge though to pull off a good frame mod and make it work. | ||
| Strokizator |
YZ80 is going to have about 11" of suspension travel front and rear. That might translate into a motard style bike but could be real difficult to reduce to 4" or so for a road racer. But what do I know? | ||
| Nuts4mc |
1) Kevin Cameron's book, "Sportbike Performance Handbook" might be a good starting point...his 1st edition goes into the evolution of the "feather bed" frame (Norton road racer) up to the latest aluminum frames from Japan...you can find it on Amazon. 2) here's a SoCal based association that races, you might be able to find some info if they have a "rules book" http://www.raceumra.com/ 3) I have stuffed different engines into different frames more than once...the most important (and overlooked) design issue IMO; is the swing arm pivot (center line) in relation to the counter shaft sprockets center line...too high or too low and your chain is sawing away at the swing arm... hth | ||
| Glitch |
With regards to suspension, I've always counted on Traxxion Dynamics (traxxion.com) They do it all, as well as answer questions! They're awesome. | ||
| Slaughter |
The UMRA is the organization out West. Raced one of their 24 hour team races. VERY helpful. Ask questions directly from the guys/gals/kids doing the racing. There are class restrictions. Mod's allowed, etc. There ARE good suspension suggestions. On our GROM, we were able to get Ohlins internals. http://www.raceumra.com/ http://www.raceumra.com/rules.html | ||
| Greg_e |
yeah, for stock 100 you can do internals on Grom/Z125. I was thinking an F1 class machine which is pretty much just displacement and tire size. | ||
| Greg_e |
So far, the only real design details I've found are a frame jig https://www.chopsource.com/frame-jigs.html And that Honda set their Moto3 bike at 22.5 degrees for the headstock. | ||
| Greg_e |
Sorry, I think that was supposed to be 24.5 degrees. Still not committed to this, but there is a large desire to do this. Might see if I can modify and existing motorcycle to my desires, cut the neck and change the angle, etc. But a custom trellis frame miniGP bike would be incredibly cool. And I could run in the outlaw class with a 250cc motor if I wanted to build it. Not sure I want that kind of speed because the injuries that come with it are far more severe. It's hard enough for me to think when the time between one corner's exit and the next's entrance is half a second (at least it seems that way). The little 125cc classes seem to be plenty for me right now and I'm still thinking that slowing down with a Grom might let me learn faster than the kind of manic pace that the KAYO seems to require. | ||
| Ourdee |
4130 chrome-moly steel. Lots of ways to source it. I used to buy 20'+ sticks. Went to a race car frame manufacturer for some once. Even E-bay for a short piece of a particular size. A jig is a must have for mass producing frames. Or keeping every thing aligned when welding. On one off designs I welded fixture locations right to my welding table. Then cut them off when done. Couple of things I've heard. 1970s: Making a mistake on a 500cc machine can often be made up for with a harder twist of the throttle. Where as the same mistake on a 125cc machine may have just cost you the race. 2010s: With hands close together; This is how much the first 90% of racing cost. Then with arms outstretched; This is how much the last 10% cost. Paraphrasing Erik talking about the high end of bike racing. | ||
| Greg_e |
Nope not high end, the goal is here: http://nyminigp.com Not really concerned with going to any level of professional racing, can't compete with the kids unless I'm in an over 40 class. And any of you in Florida, you need to look at the South Florida miniGP http://sflminigp.com A lot of their kids have gained enough experience to move up to the 250/300 class, but they have a very active Grom/Z125 class and 40+ stock 100 class. And race all year long! | ||
| Fast1075 |
That Kart track in Orlando looks fun. Do they have an old guy on a scooter class? I still have a race suit. | ||
| Greg_e |
Probably! Best way is to send them an email. Might need to upgrade to a dirt bike on track tires like a TTR125L (L for large tires???) this would be stock 100 and 40+ stock 100 class. | ||
| Greg_e |
Nothing to do with motorcycles, but very cool and fairly motivational. https://www.youtube.com/channel/UCcXhhVwCT6_WqjkEn iejRJQ Yes this idea is still eating at me. Going back and forth between chrome steel tubes and welding a pentagonal aluminum perimeter frame. The aluminum frame is enticing because I could easily put enough fuel in there for about an hour of running. A sprint is less than half a gallon of fuel with these little engines. Need a workshop and to be able to quit my job! (Message edited by greg_e on February 03, 2018) (Message edited by greg_e on February 03, 2018) | ||
| Slaughter |
I have a spare XB chassis... 125 motors can be had cheap. Hmmm | ||
| Greg_e |
I think the full size wheels will be a problem. You'd be pushed into F1 which means fighting things out with 180 pound bikes. You'd want to build a really good motor. |
