Mechbuilds Projects

[Mechbuilds]

UPDATE:

Axles done, chassis done. The diff lock mechanism on the rear axle could do some work but it works for now. 

Pics:












The suspension is sooooo smooootth.. I think this is the smoothest suspension i've ever built from lego. The black springs can barely handle the weight after putting the hearse body shell on top of it. 




Anyways. After this project is done, i'll return back to the drift car project. 
It will have two buggy motors. One for each axle. 



Cheers!

[Mechbuilds]

While the 4x4 project is waiting for parts, i already started working on the drifter. 

Here is the current wip:



Two buggy motors joined together. Both have their own axle. Should i combine the motors so they work together or keep them separate? 
Do i gain more torque or does it matter? 

Currently there are two 4 long axles that have those yellow bushings and a beam in the middle to stop the axle from pushing in. 
I could replace that with a 9 long axle and build a brace inside that holds the axle centered. 

The more i think about it, the more i want to use just one single axle. 

[Mechbuilds]

Current state of drift car:










I have a feeling that i have too much power and this thing will just make donuts.. 

Size is 17 studs between hub mount points. 
How long should i make the chassis? 

[Jurss]

You will just brake u&cv joints, thats all :)

Lenght ~2.5 width.

Edited November 30, 2020 by Jurss

[Mechbuilds]

7 minutes ago, Jurss said:

You will just brake u&cv joints, thats all :)

Lenght ~2.5 width.

How am i going to break the U&CV joints when it's a low torque application? 
I'm using chinese fake tyres which are very hard and not that grippy. 

EDIT:
25 studs total width means 62,5 studs of total length. 
I guess it could be a stud or two shorter. From hub to hub perhaps 35 studs? 

Edited November 30, 2020 by Mechbuilds

[amorti]

Keep it light and you might be ok, but you're definitely going to find out what it sounds like when a U joint snaps eventually.

Keep the U joints as flat as you can, keep both ends as well supported as you can (e.g. mount the wishbones and wheel hubs with friction pins, not loose pins or axles), and say a little prayer each time you flick from forwards to backwards on your control.

Might be worth looking at whether you could use universal joints both top and bottom, rather than CV joints. Then you can use metal u joints.

https://rebrickable.com/mocs/MOC-11088/Didumos/turn-table-based-wheel-hub/#details

Edit: is that a universal joint at the top of the driveshaft which doesn't have its pivot aligned with the suspension pivot?

I'll leave this here 

 

 

Edited November 30, 2020 by amorti

[Mechbuilds]

You are correct on the U joint not aligned with the suspension pivot. 
However if you build it in real life and try it, it works. everything seems to work smoothly. 
There is no other possible way to make it work with an independent suspension in this scale. It's 25 studs from edge of wheel to the other. (17 studs between hub mounting points.)

Unless you have another suggestion then i'm all ears. This is a difficult scale to work with. 

The front axle has only 1 stud of suspension travel. If the rear would match the front axle suspension travel then all the better. 
Really open for suggestions here.. 

[amorti]

They might be fine for a while, but I have busted several U-joints and also snapped the heads clean off of CV joints on several occasions, and I'd say that's where this would go too.

If it does that, either drop the suspension and use a straight axle instead, or try those turntable hubs from didumos, and use metal u-joints through them.

Or turn the buggy motors around to be used as swingarms, ditch the differential (there's at least a small chance that'll spit its gears out, btw) and the joints in one swoop.

[Mechbuilds]

24 minutes ago, amorti said:

They might be fine for a while, but I have busted several U-joints and also snapped the heads clean off of CV joints on several occasions, and I'd say that's where this would go too.

If it does that, either drop the suspension and use a straight axle instead, or try those turntable hubs from didumos, and use metal u-joints through them.

Would be impossible to have a suspension then. If you look at the buggy motors, they're facing forward. There is going to be a fake engine on top of that rear axle. 
If the axle was a solid axle, the only suspension with no U joints in between would be a pendular suspension. 
If i had a solid axle with suspension, the suspension would have to include the buggy motors too. That would be a massive chunk of stuff suspended. 

Considering i have to fit interior, fake engine, openable hood for the enginebay and all that stuff, it would be pretty compact and crowded to have all the features. 


What i'm looking for is a model car like the lamborgihini so you can put it on a shelf and look at it. push down on it to show it has suspension, and have all that good stuff.. 
But you could also power on the buwizz and drive it. Two buggy motors would give it enough power to kick the tail loose. 



EDIT: 

I can just swap the U joints to CV joints.. DOIII!!! 

Edited November 30, 2020 by Mechbuilds

[Mechbuilds]

Removed the U joints and changed them to CV joints. Went full speed and grabbed the wheel with my hand. It completely hard stopped the 2 buggy motors and it went to power saving mode. Did this 5 times on a row and no damage anywhere. 
Seems fine! 

[amorti]

Is that with Lego battery box and IR receiver? V1 or V2? 

Buggy motors can take 3.2A stall current. IR v1 gives 0.4A per channel, v2 gives 1.5A per channel. The normal battery box is 0.75A fused. So you'll trip the safeties on the battery and control unit waaaay before the motors.

On the other hand Buwizz gives 4A continuous with 6.5A accepted for a short time. So if you're planning to upgrade the power supply, that's when you'll see stuff break. If you're not, you're going to be disappointed with what your 2 buggy motors manage.

Edited November 30, 2020 by amorti

[Mechbuilds]

28 minutes ago, amorti said:

Is that with Lego battery box and IR receiver? V1 or V2? 

Buggy motors can take 3.2A stall current. IR v1 gives 0.4A per channel, v2 gives 1.5A per channel. The normal battery box is 0.75A fused. So you'll trip the safeties on the battery and control unit waaaay before the motors.

On the other hand Buwizz gives 4A continuous with 6.5A accepted for a short time. So if you're planning to upgrade the power supply, that's when you'll see stuff break. If you're not, you're going to be disappointed with what your 2 buggy motors manage.

I will be using buwizz. The battery box and reciever is there only to test the steering because it's just much faster to use the battery box and IR reciever to quickly check than opening up your phone, starting bluetooth, connecting to buwizz and doing it that way. 


EDIT:

I mean there is enough power to make the axle jump when i grab the wheel. The whole axle jumps up in my hands before the motor stops spinning. If i hold the power on, i can pretty much hold the wheel and make the motors float. All that weight on the CV axles. 
But i don't see any parts snapping because of the power. Everything is working fine. You can build the same axle yourself and try it. 

Edited November 30, 2020 by Mechbuilds

[amorti]

I don't have any RC motors, but I've snapped plenty of CV joints with 4* L motors (Icarus) to know they have limitations. When mine have broken, the head snaps clean off the shaft and stays in the female part. 

[Mechbuilds]

9 minutes ago, amorti said:

I don't have any RC motors, but I've snapped plenty of CV joints with 4* L motors (Icarus) to know they have limitations. When mine have broken, the head snaps clean off the shaft and stays in the female part. 

The L motor has more torque than the buggy motor. 

https://www.philohome.com/motors/motorcomp.htm

Buggy motor is all about speed. High RPM. It doesn't translate to high torque.. 
I've managed to snap U joints when using buwizz and XL motors. Simply by going forward and backward fast. 
I'm pretty sure on this application the buggy motors will just stall due to the gearing. 
Using harder rubber tyres (chinese copy) will have less grip than standard lego tyres.. 
So the tyres will probably just slip due to the light chassis. 

[Mechbuilds]

I'm back! 

I'm currently working on a trail truck. With some help i've managed to modify an upgraded version of @Attika's Ultimate pickup's chassis. 
Now that the chassis is done, i'm trying to figure out a gearbox for this so i get fast speed for travelling and slow for crawling. 
The suspension is soft and saggy so i need to make it stiffer. My plan is to add additional springs to the center control arms. That way i can keep the long springs and get good suspension travel while getting no sag on the chassis. 
Doing this will allow me to have softer spring tension when the chassis needs to flex. But also give me a stiffer suspension in the center so i can put more weight on the chassis. 


Pictures:

[Mechbuilds]

Update:





i like this enginebay design but i'm not sure about the bodywork. I feel like it's too wide which will make it challenging to build the rest of the bodywork.. 
I feel like i could make the bodywork better.. 

[Mechbuilds]

Some progress made on the chassis.

 



I'm quite happy with the steering and suspension.. 

After i figure out some sort of gearbox for this, i can start working on the body. 


EDIT:
Yeah the point of the suspension is to have a stiff up and down movement by having the center control arm push the axle down. But still a soft tilting motion when crawling over rocks thanks to the soft springs. 

Edited July 17, 2021 by Mechbuilds

[Jurss]

Engine looks good.

[1gor]

Looks very interesting; tumbler tires are beautiful; pity there are not tires less than 30mm wide with the same pattern.

[Mechbuilds]

It's been a while since i've posted anything.. Time to resurrect from the dead.. With a new project. "shocking".. 

Okay so since @keymaker did the chevy build, i've finally found the truck shape i'm looking for. So after a little bit of copying and also receiving some help from keymaker himself, i've managed to start my own project.
Dodge ram pickup:




Note: The front mask is missing a couple of pieces.. Need to order those gray 1x1 bricks so i can fill in the gap next to the front headlights.

But i'm very pleased how the front maks turned out. It also has that curvy shape on the grille and the vertical gray line that the dodge has.



Now i'm quite stuck with the chassis. Since the keymakers chevy chassis is shorter and narrower than this dodge, i needed to widen the front axle.. While this size increase will let me add more functions like springs for the suspension and a differential to make this thing turn, i'm still facing my greatest weakness.. I can't really make solid axles..

here is an LDD of where everything needs to be:




I've toyed around with a similar steering solution than the @rm8 FJ-40 has and it seems to be the best solution to keep the wheels straight when the suspension/chassis is flexing when crawling rocks.
But if i have a steering rack, i can mount the servo inside the chassis and give me room under the bonnet.. But that also has issues.. The axle will be very bulky and it will steer when suspension/chassis is flexing.
I did check for room under the hood and if the servo is mounted on it's side, there is enough room for it to be there and the hood to close.

I'm not really looking for insane amount of flex but just a working suspension so the thing is driveable..

The mustang wheels help to get better geometry since i can get the tire very close to the pivot point.
What makes this a challenge is using no hubs but an axle connection instead. The jeep tires really fit this scale and makes the pickup truck look more realistic to scale instead of having "monster truck tires"..

Any suggestions on the axle and suspension will be appreciated.
 

[Mechbuilds]

Update:



Rear bed and rear axle + rear part of the chassis complete.. 

To do list:
-Power transfer
-Front axle
-Finish the chassis
-Interior

[Mechbuilds]

The dodge ram is finished!

[Mechbuilds]

I designed the toughest driveshaft you can build from lego. 

Introducing the hub-joint:



You can choose to either connect the middle hubs together and even connect the axle to them so it can spin or you can decide not to connect them. 



After trying it in real life, it's so darn strong that you can stall an XL motor with zero damage to the driveshaft. 

The 9 long beams are not necessary though.. You can just remove them and the light gray hub connector part and just have the 3 stud connector only and it'll work just the same.
However if you want to limit axle bending, i recommend connecting the center axle to the beam assembly and having the beams rotate as well. 

You can get 3 stud of travel in one direction so basically 7 studs total. That's huge with a driveshaft this short.. You can also make it as long as you want and get even more travel. 
This can be used in large mocs that really need a very strong driveshaft due to massive torque. 
Bonus for this is that it can also be made quite telescopic. Axles have 3 studs to move telescopically before they hit the pulleys. 

Edited October 26, 2022 by Mechbuilds

[2GodBDGlory]

Nice idea for a heavy-duty CV joint! I feel like I've put hubs together like that before, but never thought of this application for them! The angle is limiting, but it's quite smooth, so I think this would be a good alternative to some of the HD U-joint designs I've seen!

[whitepen]

7 hours ago, Mechbuilds said:

I designed the toughest driveshaft you can build from lego. 

Introducing the hub-joint:

This seems like something @Zerobricks would make!