RC Cheap Baja bike

[piterx]

Hello everyone!
I was wondering if it was possible making a bike that was fun to drive around while keeping it low price so i came up with this:
it's a baja bike, it runs on an L motor geared up 2:1 and like the other bikes i've been making it shares the same principle to keep it upright.
These new tires are awesome, they have an amazing grip and the rounded shape makes em really good for motorbikes!

I hope you'll like it, here are some pics and the video i shot :)

Edited April 3, 2021 by piterx

[keymaker]

I am not into motorbikes but man, great work with this balance/steering mechanism. Simple and effective and those new tires are really great for such constructions.

[amorti]

Looks good! Slower, easier than the fast bike.

Will have a go later on. I don't have the tyres but I probably have the rest.

Have a look at these motors, they're almost twice as fast as Lego motors and have more torque too. Should be great for this?

https://www.custombricks.de/motors-cables-sbrick/cada-power-functions-l-motor.html

 

 

 

 

 

Edited April 3, 2021 by amorti

[piterx]

15 minutes ago, keymaker said:

I am not into motorbikes but man, great work with this balance/steering mechanism. Simple and effective and those new tires are really great for such constructions.

thank you dude! yeah those tires are awesome

 

13 minutes ago, amorti said:

Looks good! Slower, easier than the fast bike.

Will have a go later on. I don't have the tyres but I probably have the rest.

Have a look at these motors, they're almost twice as fast as Lego motors and have more torque too. Should be great for this?

https://www.custombricks.de/motors-cables-sbrick/cada-power-functions-l-motor.html

 

 

 

 

 

yeah dude definitely try it out! it's really simple to control, you can use the old futuristic wheels as well they fit :)
i've never seen that motor! that's cool actually!

[amorti]

Don't have those either, nearest I have is probably 81.6 balloon tyres (too wide), or Arocs tyres (too square).

I'll build it! It'll just have to wait until a next bricklink order to get the tyres.

Would you mind sharing the studio / LDD file? Btw, sure this and the other one would do well on rebrickable if you decided to make instructions for it. I've never made instructions but it seems like you have done the hard part already by digitising it. I know I'd happily put a few sheckels for it.

Edited April 3, 2021 by amorti

[SaperPL]

This is really cool. You could figure out a way to submit it to Lego Ideas (would it work with PF IR and lego battery box?) unless you want to sell instructions for it.
This is really something fresh and this could be actual entry level RC kit.

Edited April 3, 2021 by SaperPL

[amorti]

@SaperPL

I think you could make it work with the two port powered up hub and two new L motors. The motors are a stud longer and the battery box a brick taller, which should be not such a big deal? The main problem is AAA batteries are a *lot* heavier than lithium cells. Even so, powered up motors can make very accurate servos, so (once you'd got started) just swing the weight less.

This one would be way more likely to be released than the fast bike (because of the buggy motor and 1990's tyres, and the fact you're definitely going to crash it and break pieces, a lot).

Edit: actually the main problem could be the PU cables hanging out the side of the battery box. They'd be very vulnerable.

Edited April 4, 2021 by amorti

[Bartybum]

I always really like these countersteering motorbikes, they're really clever. Also, cute kitty

[SaperPL]

3 hours ago, amorti said:

@SaperPL

I think you could make it work with the two port powered up hub and two new L motors. The motors are a stud longer and the battery box a brick taller, which should be not such a big deal? The main problem is AAA batteries are a *lot* heavier than lithium cells. Even so, powered up motors can make very accurate servos, so (once you'd got started) just swing the weight less.

 This one would be way more likely to be released than the fast bike (because of the buggy motor and 1990's tyres, and the fact you're definitely going to crash it and break pieces, a lot).

 Edit: actually the main problem could be the PU cables hanging out the side of the battery box. They'd be very vulnerable.

I'm not so sure that the issue with cables would be that big if they could be guided, unless the bike tips over at speed which isn't good for cables, I think.
Overall because of the motors length and battery box height the thing would be longer, but since you get same L-motor on the side, the construction could be symmetrical which may simplify things.

[1gor]

Cool project  and I see your Tom cat is playful. My Tabby cat is on patrol (again)

[amorti]

I don't have suitable tyres yet, but anyway I built it.

It's built with CaDA Pro motors.

1. CaDA servos aren't proportional, but I'm all out of accessible Lego servos and they cost 80€ each now.
2. CaDA L-motors have been measured here at 715rpm versus 388rpm for Lego, pulling 2049mW, which is nearly double what a Lego motor pulls.

Noting that I could make the bevels click by hand, I've beefed up the bevel box. I used a CaDA 20z gear, as the teeth on them are squarer and less prone to skipping.

Experience tells me this motor will happily pull 20:12 gearing giving 715* 20:12 =  1191rpm, which is about the same speed as a buggy motor. Even flipping the gears to 12:20, it'll have 50rpm's more than a Lego motor, so probably just do burnouts eveywhere. The space also allows for two black gears giving 1:1, but I want to keep the CaDA 20z gear in there.

@piterx, any ideas if this will cause an issue for ground clearance and self-righting, either with futuristic tyres or baja tyres? I'm looking at that bush-pin at the bottom (replicated on the other side just for table-testing of the motors). If it's close, it could also be a slightly smaller pin-pin-axle, I would even snip the end of it, but I can't get rid of it completely.

The only other mod I did was to support the ends of the steering slider axle and add an 8z gear on the other end of the gear rack, as without that, the 8z gear tends to skip across the gear rack.

Guess I need to get on Bricklink and order up some tyres 

I'm tempted to get the Futuristic wheels as a quick mock-up on Stud.io says they *should* allow the bevel box to go inside the frame. I could use either the skinny or the fat one up front. There again, new spiky tyres look great and maybe the extra sidewall height provides some rear suspension. I'm open to opinions - please, let's hear them :)

Edited April 4, 2021 by amorti

[2GodBDGlory]

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.

[amorti]

In the CAD renderings, it's geared black 12z to grey thin 12z.

It's easy to get various combinations of 12/12, 12/20, or 20/12, but that's all you can easily do. I guess you could get the new 28z gears involved with a bit more effort, but it still wouldn't be 2:1.

Edited April 4, 2021 by amorti

[2GodBDGlory]

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!

[amorti]

I've not driven one yet, but I suspect it'll be pretty important. Otherwise the bike will be very unstable if all you have is bang-bang steering. Your question got me thinking, to the point I've just played servo Tetris and got a proper Lego one for both these bikes.

Balloon tyres won't work on this bike as it's designed, they're too wide. Probably too big on the radius too. That's not to say you couldn't make it work. Just put an extra angled beam in the middle of the frame and change the pins around, should be possible. Should also be possible to put the frame one more stud further back as needed.

[piterx]

hey guys! so: 
- the 81.6 dont fit and you will have to widen the chassis one more stud (but i might do it for you one of these days)
- it works with standard PF lithium battery and the steering doesnt get too compromised. The only problem would be the range and the speed that will make it go like the driver was drunk :D
try building this one if you don't have the new wheels, it was the original model i made a while a go but i wasn't too happy with it, it was working really good but it was still bulky here and there, like the gear rack part, that sucks big time, the new one is so much cleaner :)

@amorti that is cool dude! even tho i believe you dont really need to reinforce it that much, i never had the gear skipping, nor there nor on the gear rack:)

Edited April 5, 2021 by piterx

[amorti]

@piterx I reckon the CaDA motor can make the bevel box skip even if a Lego motor cant. Anyway, I can't help myself 

I picked up this cross-bracing habit from Didumos (a pinhole not used is one wasted) and until the tyres arrive, all I can do is tinker at it.

What do you think about the futuristic wheels? I like the idea of putting the bevel on the inside but I'm not sold on the rubber-band tyres.

[piterx]

20 hours ago, amorti said:

@piterx I reckon the CaDA motor can make the bevel box skip even if a Lego motor cant. Anyway, I can't help myself 

I picked up this cross-bracing habit from Didumos (a pinhole not used is one wasted) and until the tyres arrive, all I can do is tinker at it.

What do you think about the futuristic wheels? I like the idea of putting the bevel on the inside but I'm not sold on the rubber-band tyres.

the futuristic wheels work really good to be honest! the only reason why i preferred the new ones over those is that they are slightly bigger so the bike goes a little faster

[amorti]

Getting the hang of Stud.io now.

Stud.io file here: https://bricksafe.com/files/A_morti/baja-bike/baja.io

There are some modifications: 

• strengthened the bevel box so it's pretty much impossible for the gears to skip now. It could fit inside the futuristic wheels but has to hang outside with the buggy wheels.
• rejigged the steering mechanism which now supports the frame backbone making the whole thing much more rigid. The steering can still skip if you force it, but I think that's unavoidable if using 8z gears.
• the main frame is now form-locked to the rear frame so it can't pull out. By ruler, the tyre should still clear  (<fingers crossed)
• The gold wheels were just a moment of madness while ordering up the tyres (not here yet) on Bricklink 
   

177 parts only! And not a single red or brown one in sight.

edit:189 - stud.io counts sub assemblies as one part :/

But it needs to be 179... Anyone out there kind enough to help me add the 69909 tyres which are not available in Stud.io? Either by doing it for me and re-uploading, or giving me some hints how to do that?

Thanks :)
 

Edited April 9, 2021 by amorti

[piterx]

2 hours ago, amorti said:

Getting the hang of Stud.io now.

Stud.io file here: https://bricksafe.com/files/A_morti/baja-bike/baja.io

There are some modifications: 

• strengthened the bevel box so it's pretty much impossible for the gears to skip now. It could fit inside the futuristic wheels but has to hang outside with the buggy wheels.
• rejigged the steering mechanism which now supports the frame backbone making the whole thing much more rigid. The steering can still skip if you force it, but I think that's unavoidable if using 8z gears.
• the main frame is now form-locked to the rear frame so it can't pull out. By ruler, the tyre should still clear  (<fingers crossed)
• The gold wheels were just a moment of madness while ordering up the tyres (not here yet) on Bricklink 
   

177 parts only! And not a single red or brown one in sight.

But it needs to be 179... Anyone out there kind enough to help me add the 69909 tyres which are not available in Stud.io? Either by doing it for me and re-uploading, or giving me some hints how to do that?

Thanks :)
 

Ill dm you the 3d model ive made to render my images :)

 

btw great job on the improvements! The golden rims look sick

Edited April 9, 2021 by piterx

[amorti]

1 hour ago, piterx said:

Ill dm you the 3d model ive made to render my images :)

btw great job on the improvements! The golden rims look sick

Thanks!

Don't know what I did, but I've not managed to make that work properly.

 

 

[2GodBDGlory]

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.

[amorti]

Cool!

Show us what you've made mate.

My best guess is instability will be due to looseness in the chassis or a lack of trail. Lego Moto suspension takes about half a kilo to get much of any compression. It won't move noticeably on a small imperfection.

 

 

[2GodBDGlory]

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!

[2GodBDGlory]

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