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Taking things too far, again.

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  • #31
    Okay, I'm getting impatient on the frame. I think I'll still make the next bends for the vertical portions and get that welded, but at that point I think I want to get things clamped together, measure and put in the inserts for where the swingarm pivot (axle?) will go. Then make a jig that I can bolt those parts of the frame to, that will also have a mount for the front axle so everything can be held together in alignment for welding the headstock. Yeah, that might mean I'm sacrificing the bearings. Maybe, maybe not. Either way, that means I need the rest of the stuff for the forks done. I've been working on the tiny bit left on the oval inserts, and have the bulk of the steering stem done. Still need to do the portion for the lower triple tree. Just got late tonight.

    All the bearings lands are done, threads are done, and I've bored some 7075 aluminum for the three nuts I'll need and have the internal threads cut to make sure everything fits together. The smaller flange at the end is just a reduced flange to provide space between the bearing and the larger flange so I can get the bearing off in the future if I need to without destroying anything. The bigger part behind that is just where I'll machine the part for the lower triple.




    And this is together with the upper triple tree. Even with just the one set screw, these are locked together with no play at all. I think with the nuts and flanges, there's going to be no issue.

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    • #32
      Saw something on a car building show regarding your fiberglass question that might help. They were reshaping a fiberglass body. Basically you could use a cardboard box and fill with expanding foam Once it dried they roughed out the shape with blades, they then sanded the final shape out. They layed the glass on the foam but you could make a reusable form first. Not sure what kind of expanding foam they used but it looked like the stuff you get at the hardware store. Awesome project.

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      • #33
        Originally posted by y2ktj View Post
        Saw something on a car building show regarding your fiberglass question that might help. They were reshaping a fiberglass body. Basically you could use a cardboard box and fill with expanding foam Once it dried they roughed out the shape with blades, they then sanded the final shape out. They layed the glass on the foam but you could make a reusable form first. Not sure what kind of expanding foam they used but it looked like the stuff you get at the hardware store. Awesome project.
        That is an awesome idea! Thank you very much for that info!

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        • #34

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          • #35
            Time for another update. I've made some more pieces. I went ahead and made all the nuts I need for the steering stem. 2 flanged hex nuts that are 24mm x 1.5 thread pitch, and the flatter nut for going under the top triple clamp, 26mm x 1.5. All of those are out of the 7075 aluminum for strength.



            I started working on some side work to help pay for the engine, and broke my shop press. But, that was an easy fix. For the evening that it was broken, I switched to working on the frame pieces again. I did the next few pie cuts and did the bends for the vertical portions. I have them upside down here just mocking things up. They are not yet welded to the headstock.





            I think before I weld the frame pieces to the headstock, I'm going to clamp things up, make some fine measurements, and then drill some holes and put some inserts into the frame for the swingarm. I've decided that here, I'm going to emulate the mounts from a CBR1000 frame. I'm going to make the sprocket side of the frame be a solid mount that will have a recess for accepting a nut on the 3/4" shaft. The other side of the frame will have an insert with internal threads somewhere between 1 to 1 1/4" diameter. That will have a threaded sleeve with a jam nut that can thread in to sandwich the swingarm with thrust bearings for a rigid mount, with a 3/4" hole for the shaft to go through. The swingarm will also have needle roller bearings pressed in.

            In other news, I've been struggling with motivation for the last few days, but I also have some good news. I was denied for going back to work yet, but in talking with the plant manager and my surgeon regarding my restrictions, I'll be able to go back in the first week of January. That means I'll start being able to move forward on purchasing parts again soon, and I'll also have time to go visit family for Christmas. All in all, I think I'm very lucky with how things worked out. For needing to take way more time than I would have wanted for shoulder surgery and recovery afterwards, things have turned out amazingly well. All in all, I'm starting to feel good enough to be able to tell that the surgery did indeed fix the issues it was supposed to. During recovery, I made good progress on building a bike from scratch, and effectively taught myself how to tig weld. Granted, there's room for improvement, but still. On top of that, work has not been pushing me at all, and I'm coming back in as my new position.

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            • #36
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              • #37
                Spent some more time in the shop today. Fixed the bearing/shaft for the gearbox on the lathe. Then I made all these pieces for making the swingarm mounts for the frame. The larger cups will get mounted in the frame. The one with the 3/4" hole on the chain side, the threaded one on the brake side. They are 6061 to weld to the frame rails. The threaded sleeve goes into the threaded cup from the inside of the frame rail. When the swingarm is made and ready to install, the threaded sleeve snugs up against the thrust bearings, and the jam nut keeps it there. Then a hollow shaft will tie it all together.





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                • #38
                  One more update. I'm trying to put a real push into this project before leaving to go visit family for Christmas, and then going back to work just after new years. I've lined everything up and clamped it in place for welding the frame, made very detailed measurements from the welding table surface, and used a wire (no stretch line string) to measure from the all-thread through the headstock. Drilled holes out for the swingarm pivots I made, cut the verticals to length, clamped it all back up and started welding.



                  In the middle of welding, after doing everything I could before needing to flip it over, I wrapped a sock around the steering stem, jammed it into the headstock, and very half-assedly tried setting it up at approximate measurements. I'm really liking the size of this thing. I'm also finding out that it is way more rigid than I expected. I was certain I'd need to do more to get this to work, like maybe 1x1 rails under the motor and up to the headstock, but I'm really thinking I won't need to bother at this point. Still have more gussets to do, but I'm impressed so far.



                  I also decided to bolt the headstock down again, and then do the swingarm pivots. Did detailed measurements, used the tube I'm going to make the axle out of and a level, and used the wire. I did not clamp the frame down though, because I didn't want that introducing flex that isn't there, so only the headstock was bolted. This was a good exercise in doing tack welds 180 degrees apart, then checking alignment again. Repeat for 4 tacks 90 degrees apart, and both sides of both inserts, making sure the axle was lined up and moved easily.





                  The stock honda grom has 3.9 inches of travel in the front, and 4.1 in the rear stock. When I do the Ohlins cartridges and springs, I'm also doing another mod which extends the forks 1" and adds that as extra suspension travel. Because of doing that, I'm planning on also adding approximately 1" of travel to the rear. At the swingarm length I have planned, just a touch over 17", that puts me at putting the R6 shock right at 6" out from the front pivot of the swingarm to have just the right amount of travel before the shock bottoms out against the rubber bumper. This is going to be direct hookup instead of linkages and dogbones. I don't feel bad, the grom uses a direct shock. So does the pocket bike I overbuilt. I did that with a Honda 954rr rear shock. It's 4.5" out, and I needed to create an extra 1/4" spring preload collar. I think with the mechanical advantage of the extra 1.5", this shock should be perfect, give or take finding a different spring if needed.
                  Last edited by ygolohcysp; 12-16-2018, 11:03 PM. Reason: Added the pic I forgot

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                  • #39
                    Did you post a concept drawing of this project? I'm sure you're building a mini slab side gsxr!!!

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                    • #40
                      Originally posted by buffalobill View Post
                      Did you post a concept drawing of this project? I'm sure you're building a mini slab side gsxr!!!
                      I thought I might have, but I guess not. I never did a very detailed drawing. I essentially took a lot of measurements off my pocket bike that works so well. I did a drawing to scale just with functionally important points like heights and angles and locations. Axles, forks, tank, seat, rear sets, swingarm pivot, etc. I then compared those to a Grom, which I don't think works well without a LOT of mods, and also compared it to a professionally built R6 race bike. It's actually quite funny how closely the pocket bike emulates the correct placement of rearsets, seat, etc (granted, all of that modified with how it sits now). Then I set about making a sort of skeleton sketch using axle heights, planned fork angle, and then drew a frame to connect those points.

                      So, this is to scale, including the R6 shock and Daytona Anima 190cc motor.



                      The specs so far is 24-25hp (as advertised as stock performance for the 190cc motor), 200 pounds or less. The bike I'm hoping to beat is listed as being 150 pounds, but it's literally the size of my pocket bike. It has a steel frame, I'm using aluminum, but I'm also over building it to survive the typical crashing involved in racing and practice. Mine is also going to be comfortable enough for an endurance race. I think my wheelbase is going to be about 1 inch longer than a Grom. 30" seat height. Enough ground clearance to be able to drag elbow if the race slicks hold well enough. That was a problem I was running into with my crf150f. I'd lean to the right, hit my knee, then my toes, then the peg mount. Then I'd throw sparks while sliding and have to push the bike back up. I did that twice while beating someone to an apex by just not hitting the brakes to get by them. I can only guess that thinking I was crashing in front of them helped them slow down a bit. LOL

                      But yeah, I essentially want real sport bike performance out of a miniGP bike. So appropriate forward to rear placement of the front of the seat and rear sets, appropriate length of swingarm and angle for anti-squat, 24 degree rake. Unfortunately, I figured out to get the braking I want, I'll need to spend about $700 on the front brakes. Brembo RCS14 master cylinder, Brembo P4 30/34 caliper, Vesrah JL compound pads, and as large of a rotor as I can use and still fit that caliper. And the only reason for that caliper is specifically because that compound of the Vesrah pads is worth it, and also not available for the stock caliper, or I think even the single piston Brembo calipers.

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                      • #41
                        The limits of physics

                        Ok, and so we can get a clear idea of the physical challenges of racing a mini bike; what's your height and weight?
                        I'm having a hard time on my Kat, because my legs are so long. My knees are a bit over bent, so I have to use more force to push up and change sides in chicanes. Fatigues my legs quickly.
                        I'm gonna raise my seat a couple inches just to reduce my knee angle.

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                        • #42
                          I'm almost 6' 1", weigh about 185. And yeah, it's my legs that suffer the most when racing. I don't feel too bad on the Kat, but I'm getting older, and my knees can't take a long time on the Kat, just general riding. After 2 hours or so, I need a break. On the crf150f, my legs feel pretty good until the end of an endurance race. On the pocket bike, my knees have had it after about 15-20 minutes. It's just so small that I'm forced to spend almost 0 time actually sitting on the seat. I'm hoping with the bike I'm building that it'll be capable enough to let me not have to hang off so far and be able to lean over further without scraping hard parts.

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                          • #43
                            Your machining skills are awesome. Your carpet and wallpaper, not so much. Lol. Great work so far.

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                            • #44
                              lmao

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                              • #45
                                Didnít even notice......too busy staring at the work. lol
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