2GodBDGlory

Yeah, the wide tires will keep the buggy motor offset, but it should be possible to get it balanced right.

Good! I'm going to start on a single buggy motor-powered, balloon tired bike now.

I just took my original balloon tire bike out with marble-stuffed tires, and the difference is quite dramatic! Where it would previously start violent shakes, particularly when speed dropped on modest uphills, it now proceeds with smooth composure, never once getting that kind of shake! The trade-off, of course, seems to be speed, because of the weight increase, but it is not accompanied by the loss of stability motorcycles typically exhibit at low speeds. This trick may be a mere bandage of sorts for poorly designed bikes, but the dramatic difference may make it worth considering. I'll also test adding weight to the tires via original Lego parts, such as axles. EDIT: Filling it with Lego parts looks like it may require more patience than I have, so I may just stick to marbles. If I were going for two, I would definitely have to use either two batteries or my high-output 9.6V pack. My only fear with using just one of that a lack of Buwizz power may reduce speed critically, but you're probably right that it is best not to overcomplicate things.

Yeah, most of the successful designs out there are small and light. I do have my balloon tire one working fairly well, but I'd like to get some more speed and refinement. A buggy motor or two would help, but it's tricky to power multiple ones without a Buwizz. Perhaps I'll try some thing like piterx's "The fastest bike," but with a PF battery and my balloon tires, or go big and use both buggy motors and my larger motorcycle tires.

That piston looks bigger than the one I took out of a rototiller! Wow!

Hmm. My modified Ducati had both high weight and a high CoG. I'm starting to feel like giving up on it and starting with a fresh design, but I'll try some more things before that. That comment about the weight of the tires has me wondering if adding weights inside the tires could increase stability. I've added marbles in the tires of off road vehicles to aid traction and lower the CoG, and maybe it could work here too? EDIT: marbles don't fit in motorcycle tires, but I could potentially see it helping with bikes made with balloon tires.

Do you guys think it is reasonable to assume that the higher the weight of the model, the faster it will need to move to stay balanced, or would weight and minimum speed be unrelated?

I've been doing a lot of freewheeling testing while moving weight bricks around, and I think it is better balanced now. It's a rainy day, though, so I can't test outside for now.

Well, I have some wheels to help it get started and steer, but they are meant to be disengaged when driving straight. If I got them more involved than that, I would give up too much challenge!

Thanks a lot! I have since added a weighted brick opposite the buggy motor, which should help a lot with weight distribution. I also completely registered the forks, sacrificing the suspension in favor of stiffness, and I increased the castor angle to nearly 45 degrees. It seems better, but my steering mechanism is jamming up now. I'll see how I can make things stiffer, and try freewheeling tests, to hopefully get this working. Motorcycles seem to require a lot more trial and error than other Technic models!

To kick off some discussion, I'd like to show my heavily modified Ducati set. It has a buggy motor for drive, with various gearings (1:1 from the fast output at present), a servo motor to move the PF rechargeable battery side to side, and a revised steering pivot. It never does seem to self balance, though. I guess this is because of: A. The center of gravity is too high (the bike is tall!) B. The imbalanced buggy motor makes it lose balance. C. The steering forks have too much slack D. It isn't fast enough. I'm going to try working on C now, but I'd appreciate advice!

I just made a topic for that, so general discussion of RC bikes can be continued over there.

Largely because of piterx's work on self-centering, RC motorcycles, there has been a fair bit of interest in these concepts lately, with a lot of discussion going on in the threads for his models. Because of this, it seemed like a good idea to start up a dedicated thread for discussion of all sorts of RC motorcycles, rather than cluttering up preexisting threads about particular models. Hopefully this thread will enable us to discuss different bikes being built, and the techniques behind them!

That's possible, thanks! Next I'm going to try to motorize my Ducati set, which could be a huge challenge! Also, this discussion is beginning to have little to do with the original post. Perhaps a new "general RC motorcycle discussion"topic should be created?

Here you go. Note that this model is essentially a personal proof of concept, by no means a finished MOC.

Maybe big stacks of 1x1 circular plates could get a good effect?

I'll try to get some pictures soon. It is entirely possible that my chassis is too loose, but I think the castor angle is about right (at least, increasing it caused big problems) Thanks!

Thanks to this model's inspiration, I now have a bike is my own up and running! It is powered by a custom battery and a PF receiver, steered by moving two weight bricks with a servo, and driven by two PF L-motors, geared 28:12. It also uses 62.8 balloon tires. It took me a lot of tries to get something working, but the result pleases me. The main issue is a tendency for the model to begin to shake wildly when going over pavement imperfections, which could be caused by its lack of any suspension.

I'd be happy to see that two speed design, if you're interested in building it!

That is a far simpler mechanism than mine was, and is probably much better to use in practice, but it does have some functional differences from mine. My design was set up so that the difference in speed between the two wheels had to exceed a fixed constant in order for anything to happen. The advantage with this is that a vehicle with my system (provided it could somehow overcome the fearsome friction involved!) could run around in circles all day without ever engaging the differential lock, because that constant was never exceeded. Only if one wheel is actually slipping, causing there to be a major difference in speed between the wheels, will the lock engage. My understanding is that your design could eventually engage the lock in routine maneuvering if the vehicle continued to rotate the same direction for too long (I don't know about @Pnumetac's design, though). I would say that my design is overcomplicated in pursuit of a theoretical ideal, while yours is much more practicable, if a bit less sophisticated. Good work, though! Italics mine! Your design sounds interesting, particularly the part I italicized! I'd be interested in seeing how this looks, especially if it would provide a more practical way to only engage the lock in a true slip situation. [By the way, seeing that you are a new user, if you want to include images in a post, you will have to host them on a different site, and then embed the image's link in your post]

Good job! I've seen plenty of 56T turntables used as ring gears, but never as planet gears until now!

I highly doubt that there will be a central differential, merely because of the amount of off road performance the model would give up. Of course, if one were included, it could easily be locked, using the fourth channel, but I'm not that optimistic about Lego adding such complexity.

I've got another question for you: When building a bike like this, how important is it to have the fine steering control that the Buwizz provides? I don't have one, so my attempts have been either pure PF, with a less precisely controlled Servo, or custom/hobby based, with a strongly performing servo, but more electrical complexity messing with the weight. Thanks!

Good job! After seeing your previous post, I spent a bit messing around, trying to build a motorcycle of my own, and I found it harder than it looks! I'll probably try some more, though, and this bike should provide additional inspiration! Can you confirm if the 81.6mm balloon tires would fit? I don't expect they do, but they would make the model accessible to more people. Also, unless I miss something, the L-motor is actually geared up 5:3, rather than the 2:1 you stated in the original post.

It's interesting how you built the bodywork before the mechanical bits! This is the opposite of how I build, which is probably why I spend all my space on functions, and can only really fit a boxy bodywork... Good job!