[MOC] Greyhound 4WD RC Buggy /w instructions - Improved rim-hub connection

[amorti]

Nope, they work fine at all angles.

I'd say the wear pattern shows they even had just a little angle to spare.

That being said, they might live longer if you set the buwizz to only reach 13/15 positions? Or at least to only use the furthest click allll the way over on the slider so you don't max steer too often? Idk.

For me the big advantage is that even if they can still wear out, they can't really fail catastrophically like the old CV joints or universal joints can because TLG has put the nubs on the hard plastic cup this time (not like the old CV joints). So they will never leave you changing a drive shaft while you wanted to be driving it. Just changing them every few battery charges.

A quick spin up in "double ludicrous" mode with the suspension on full hang and at full steering says it's fine. Will report back again when I've driven it about a while.

Edited April 8, 2020 by amorti

[amorti]

1.5km later, bit of Fast, bit of Ludicrous, down some steps, up and down some curbs. Plenty of full lock steering...

Bit of wear already... But nothing snapped.

The red beams didn't have enough friction holding them on and could drop into the hub causing a click. This is better, has less slack, and now the parts really have nowhere to go.

Edited April 8, 2020 by amorti

[amorti]

Of course those 3L axles with a stud don't work, there's just enough space that the stud falls out and then you have no drive on that wheel.

You also can't use them inserted through the pulley wheel. There's only space for one half bush between the hub and the rim to hold them, which isn't enough; they work themselves loose quick enough that I quit before they had a chance to fall into the moving parts.

The most stable way I've found so far is a blue 3L pin with the single side into the wheel. It's not ideal but it seems sturdy so far.

@Didumos69 did you consider large ball joints for this? I think maybe you could fit this socket where the ball joints are on the front wishbones, and these guys where you have the small wishbones.

This video gave me the thought, after I was looking for videos of how much play might be "normal" in the normal small Lego ball joints.

 

Edited April 13, 2020 by amorti

[13h3r]

This looks absolutely fantastic.

I am not 100% this is a correct place to ask, but what is the best basic set to start assembling this? 

Thanks! 

[amorti]

In terms of getting the pieces there's a fair few rare or expensive bits in there that you won't readily get in any set. For a start: 8 unimog struts at 15€ each, a servo at 25€, 4 L motors at 15€ each, 2 buwizz at 100€ a pop.

That's approximate prices for original Lego parts ordered on bricklink.

[zux]

Some suggested sets to begin with. Although, as mentioned above, there is a fair amount of expensive parts you may need to acquire additionally.

[Didumos69]

On 4/13/2020 at 11:03 PM, amorti said:

Of course those 3L axles with a stud don't work, there's just enough space that the stud falls out and then you have no drive on that wheel.

Have you tried flipping the rim? Then the CV-joint enters the axle hole of the rim by a full stud. The only other thing you would need to change is that you need to use 3L thin levers at the outer ends, not the levers with a pin at one end and axle hole at the other end. I haven't tried this myself, but as far as I could judge in Stud.io, this should fit.

On 3/19/2020 at 10:08 PM, amorti said:

If you put the wheel the other side out, you'll get half a stud of connection into the wheel, but also a little play between wheel and turntable, enough that the whole thing shakes.

If you use the wheel the other side around, you should have a full stud connection. It could be that when you tried it was these parts  preventing the wheel to slide over far enough. The outer ends of the 6 pinhole have some extra ridges. That might also explain why you had space between the turn table and the rim.

Edited April 30, 2020 by Didumos69

[amorti]

I originally put it back together with the wheels in stock configuration and woke up one morning realising they could now go the other way - funny what happens when you stare at things too long late in the evening.

The final configuration is as follows. The pulley wheel is removed, it's redundant now the wheel is reversed (this would maybe better stabilise the drive axle if using the universal joint too)

I'm not certain having those 3L pins partly-inserted in the wheel rim is legal, but I can say it gives a better connection between the wheel and the hub to have pins in the pin holes of the wheel, than axles in the pin holes. I found before the model would make various creaking noises as the wheel shifted about on the hub, and now it doesn't.

There is half a stud of the 3L pin sticking out which helps stabilise the bracing bar. The bracing bar now only really has the job of stopping the wheel from popping off, it's not really needed as part of the rotation any more.

Again, all my findings should be considered that the turntables and tyres are original Lego, but much of the rest is from CaDA bricks not Lego.

Edited April 30, 2020 by amorti

[Didumos69]

Right. Cool! Thanks for sharing @amorti!

[amorti]

2 hours ago, Didumos69 said:

If you use the wheel the other side around, you should have a full stud connection. It could be that when you tried it was these parts  preventing the wheel to slide over far enough. The outer ends of the 6 pinhole have some extra ridges. That might also explain why you had space between the turn table and the rim.

It was exactly that. I also think that because those parts are connected via the next hole of the turntable, they allow some slack in the original configuration.

 

Ps. I'll quit editing posts if you will ?

Did anyone consider large ball joints for the front arms?

It looks like it'd be easy to fit them  in the existing space, but I don't have any and am reluctant to order them in case they don't fit the gap.

 @Didumos69 it might not be your style because it seems you have to sand the balls a little to make them move easy?

Edited April 30, 2020 by amorti

[Didumos69]

14 hours ago, amorti said:

Did anyone consider large ball joints for the front arms?

For me it's not an option to polish these balls until they move smoothly. It would feel like modifying parts, and that's one bridge too far for me. Using the blue pins as you do to tie the rim to the turntable is perfectly fine with me though, even though others would say it's not completely legal.

[amorti]

Thought it will be the case, and fair enough.

I've been battling my conscience with this:

https://www.bricklink.com/v2/catalog/catalogitem.page?P=32251#T=S&O={"iconly":0}

You could hack it into a 7L liftarm with cross holes at each end to mount the ball joints.

I never felt Lego bricks are in any way holy and I wouldn't mind polishing, but I'm not quite there to totally hack them up.

[gregorski904]

 

https://www.youtube.com/watch?v=_NSNjkMRzSU

 

Edited June 2, 2020 by gregorski904

[Didumos69]

32 minutes ago, gregorski904 said:

https://youtu.be/_NSNjkMRzSU

Cool! I like this short video too...

 

[benxz]

Guys, one of my turntables popped out recently. Anyone had this happened before? Anyway to fix or have to replace a new one? thx

[Didumos69]

5 hours ago, benxz said:

Guys, one of my turntables popped out recently. Anyone had this happened before? Anyway to fix or have to replace a new one? thx

Normally you should be able to click them together again with some force.

[amorti]

Turntable are really hard to get open, with much better retention than a usual 3-pin hub. I've never had one pop out.

However, I guess if you didn't lubricate the turntables, the retaining clips could wear out?

I did order 4x turntables to have as spares "just in case", but I haven't needed them.

[benxz]

yes, it looks like the retaining clips wore out, it doesn't clip anymore. thx for the quick reply.

[amorti]

OK, you know what to do. Replace the broken one, and any others which have become loose with new parts. Lubricate before you clip them together!

I recommend silicon grease (you might find it called red rubber grease, dielectric grease) for lubricating as it's plastic-safe. Silicon sprays such as GT85 will help but it's thin and won't last so long.

Do not use mineral based greases such as lithium grease, wd40, or Vaseline as they are bad for the plastic.

Edited June 23, 2020 by amorti

[benxz]

On 6/23/2020 at 6:51 AM, amorti said:

OK, you know what to do. Replace the broken one, and any others which have become loose with new parts. Lubricate before you clip them together!

I recommend silicon grease (you might find it called red rubber grease, dielectric grease) for lubricating as it's plastic-safe. Silicon sprays such as GT85 will help but it's thin and won't last so long.

Do not use mineral based greases such as lithium grease, wd40, or Vaseline as they are bad for the plastic.

i thought silicon spray will dissolve the plastic? as is mentioned on page 5 of this thread. Silicon grease will not?

[amorti]

20 minutes ago, benxz said:

i thought silicon spray will dissolve the plastic? as is mentioned on page 5 of this thread. Silicon grease will not?

Good point, and quite possibly, so I'llqualify my statement.

I can personally attest that dielectric grease has caused no damage to my Lego pieces over a long enough test for me to be happy to use it in any moving parts. Shouldn't be a surprise either since part of the product's design brief is to not damage plastic wire insulation.

For the same reason I would have no reservations about using red rubber grease in any application which demanded a thicker grease. Might be too thick for most Lego applications though.

I've used gt85 to shine up motorcycle fairings (also ABS but not quite same because painted on the outside) with no ill effect. Not tried it on Lego and even if it says safe for plastic on it, the risk would be your own as any spray has propellants and those can potentially give you problems.

@Didumos69 it's not pure but maybe it's something you'd consider? I've now fitted some of these in the front axle.

https://a.aliexpress.com/_dVVIOhk

The quality is... Well, it's a bit alie.

They fit loose on an axle, but they neither slip nor damage the axle. Just a little looser than old CV joints I'd say. 

They turn freely.

They don't break!

Edited June 24, 2020 by amorti

[astyanax]

@amorti Nice, I ordered those U-joints a while back too. Haven't arrived yet though. My expectations aren't too high, but I was curious enough to hit "order"

[benxz]

2 hours ago, amorti said:

@Didumos69 it's not pure but maybe it's something you'd consider? I've now fitted some of these in the front axle.

https://a.aliexpress.com/_dVVIOhk

The quality is... Well, it's a bit alie.

They fit loose on an axle, but they neither slip nor damage the axle. Just a little looser than old CV joints I'd say. 

They turn freely.

They don't break!

looks good, will get some.

[amorti]

@astyanax they're strong enough for greyhound, which I have running on two buwizz and with +30% Chinese L-motors which really do give some 30% extra power and speed.

Not sure there's much more you could reasonably ask a U joint to do.

I did splash some silicon grease on them for good luck. Silicon in case if splash on plastic parts 

[Toshi]

Hi, I have been reading in the forum for a while, but did not sign up until now...

Seeing @amorti talk about L-Motors with 30% more power made me very curious! 

Can you please share some more details about these motors?