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Lunch Box rear suspension... that old chestnut

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Oh and here is some more video from the other day.
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I tried to go out yesterday and get some more video after adding thicket oil to the dampers. It wasΒ last day of dry weatherΒ but one of the gearbox mount parts cracked and I'm out of spares at the moment. That's a part that could really do with being made from alloy.

I can't really fault the 3d printed part in terms or print quality as it cracked diagonally in the opposite direction to the print layers so I think it's just a case of the material (PETG) not being able to cope with the forces from all that suspension movement plus the aggressive driving I've been doing. I think my links have gotten slightly asymmetrical somewhere along the line too which has probably caused an uneven distribution of load but either way, I think a stronger solution would be good.

Will get more video soon when it dries up again.

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Man , that thing is on rails !! . I still need to properly shake down my Ultima LB rear end . I hope it is as good as yours , if it's half as good I'll be happy

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That's amazing!! Possibly the best handling CW-01 on Earth! πŸ‘πŸ‘πŸ‘‹πŸ‘‹πŸ‘‹πŸ‘‹

Those parts probably should be made out of Alloy... But 3D Printed media is getting better by the day.

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18 hours ago, Carmine A said:

That's amazing!! Possibly the best handling CW-01 on Earth! πŸ‘πŸ‘πŸ‘‹πŸ‘‹πŸ‘‹πŸ‘‹

Those parts probably should be made out of Alloy... But 3D Printed media is getting better by the day.

To be fair, it's just the chassis side mounts that seem to be prone to breaking, the other parts are still the original ones I put on there.
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I've had a fair few of the Tamiya ball studs pull out or even pop off so I started adding brass inserts that you heat up and melt into place. That has moved the weak point along to the next part which appears to be these mounts. Again, I can't fault the print as the layers didn't separate or anything, just reached the material limits I think (PETG) there are other materials but it seems to make the price rise dramatically.


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I might try and just hobble some of those out of aluminium. I think the other parts will probably be ok as they are for the most part.Β 

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Like I said, 3D Printing technology is catching up... But that doesn't help you now.Β 

How about making those bits out of thick ABS, or Kydex, which is even stronger?? May involve some creative carving, maybe laminating a few sheets together to make a thicker piece. 😊 

That's what we used to do back in the ancient times, before 3D Printing!! 😜  It might just work. OR.... If you have access to the equipment, make them from Alumininium. πŸ˜‰

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15 hours ago, nowinaminute said:

I might try and just hobble some of those out of aluminium

Shouldn't be that difficult t.b.h. - a vice , hacksaw, 3mm tap set and some good files should see it off .

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@nowinaminuteΒ I paused yourΒ video a few times when you turn around in front of the camera. It looks like you've got amazing rear suspension articulation. Nice!

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Got a bit more video the other day of torture testing it on ruts. This is basically what I wanted to get the other day but it was getting dark so the camera had gone into potato mode.

It was pretty much un-drivable over this stuff when it had the stock rear end and even when I first added 4-link it was was all over the place. The difference now is crazy.
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Could do with slightly thicker oil in the dampers still and maybe springs a hair firmer but I'm not decided about that yet, I'd rather it sag and droop a little if it means it's this responsive to the terrain.

I got some slow motion too which I will post soon.

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Oh and PS: I didn't realise those silly beeps were in the music till after I uploaded itΒ :lol:Β I added the song and the first few seconds sounded fine so I stuck it on youtube. It wasn't a deliberate attempt at being cheesy lol

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Here's some slo-mo. Really amazed by how it did considering the terrain, not perfect but the important thing isΒ it would bounce all over the place before on the same ground.
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Totally amazing. Maybe you can offset the cost of printing these parts by selling some kits to the rest of us! I’d buy one.Β 
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Can you share more details?? Shocks, springs, oils weights? I never got mine as dialed as yours is.

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What is going on up front? CRP kit or Ampro kit?

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On 5/15/2021 at 10:41 PM, smirk-racing said:

Totally amazing. Maybe you can offset the cost of printing these parts by selling some kits to the rest of us! I’d buy one.Β 
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Can you share more details?? Shocks, springs, oils weights? I never got mine as dialed as yours is.

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What is going on up front? CRP kit or Ampro kit?

There's some info on the previous page.

The shocks are just generic internal spring crawler style dampers. It has to be skinny ones to avoid fouling the links.

Between mounting them way onboard and them being crawler shocks, the springs are way too soft. I ended up mounting extra springs on the outside so each shock has 2 springs each, one internal and one outside.Β It's still slightly too soft IMO.

I'm using 5000cst damper oil which is about right for these shocks. The leverage from mounting them in close means you need firm springs and thick oil toΒ get it to behave like it would with suspension in the conventional location.

I ideally want to get firmer springs but it's not that straight forward as these kind of dampers are more oriented toward crawlers. I know RC4WD does a set of springs though and some of the cheap options on aliexpress come with extra springs.

You can put a spacer inside the shock too to adjust ride height but of course this doesn't change the spring rate, only the amount of force needed before the shock will actually move.

I will keep playing around with things and try and get a more optimal setup but it's already pretty cool. Springs could be a hair firmer for sure and I would rather just have the internal spring rather than having one on the outside too but I don't want to go TOO firm as it will start to negate the benefit of mounting them inwards so far.

One thing I might try is some really short touring type shocks with really firm springs, I would be able to mount them on the upper links so they wouldn't interfere with the bottom links. They dont need much travel because they will be mounted right near the pivot point and a tiny amount of movement at the damper will translate to a large movement at the axle. Think a little like the cantilever on a Traxxas e revo and summit, they only need teeny little dampers to achieve huge suspension articulation because of the setup.

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Right ! . So I have been thinking about this 4 link thing and I have drawn on inspiration from others to boot this into practice . Thanks to 'nowinaminute' for the initial thought to 'ave a go !! . I went for the 4 low level parallel links and panhard bar route . I rotated the axle to give a bit more clearance underneath and give the original pivot tube a new purpose as a bumper - kicked up a bit . The original 'Hi-lift' gearbox mounts have been re-made in 6mm aluminium with a longer lower leg to take the panhard bar mountΒ  , and the what was the rear damper mount parts are reversed and re-made in alumium too . I used short dampers mounted to the upper links as per 'nowinaminute's' future plans ? . The front is still bone stock , but lowered by 10mm to take out some of the goofy camber changes - it works too , still with a slight tow in it handles well . I used a stock 540 and a 1060 ESC to try out with but will uprate the motor later . I have to say that it handles better than any F & R converted LB I've madeΒ  , and I've made a few I can say . Even with a 540 stock it digs in at the back and there is no stiff 'bounce' of the stock rear , even to the point of raising one front wheel on the turn . The articulation is far better than stock or any of my previous conversions . More work to follow I think .Not sure if I will convert the front to double wishbone yet , but I probably will ;)

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Awesome work mate!Β 

I know some people think it kills the charm of the chassis but to me it makes it something new and interesting in it's own right but it's still imperfect enough to retain some of the crude charm!

I really need to try a bit harder at hand forging stuff. I love how my Lunchbox handles now but that's in no small part thanks to someone helping with the design. I can envision stuff but I'm not very good at actually designing or fabricating, at least not to a high degree.

I can't even put into words how much I would love to do with one of my big Nikko F150s what has been done to theΒ Lunchbox but as the chassis and gearbox have some not insignificant differences, it will require a lot of variations. I would really love to make the rear suspension work on one of those trucks.Β 

It's really great that we can inspire each other like this.Β B)

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On 5/31/2021 at 8:40 PM, nowinaminute said:

Awesome work mate!Β 

I know some people think it kills the charm of the chassis but to me it makes it something new and interesting in it's own right but it's still imperfect enough to retain some of the crude charm!

I really need to try a bit harder at hand forging stuff. I love how my Lunchbox handles now but that's in no small part thanks to someone helping with the design. I can envision stuff but I'm not very good at actually designing or fabricating, at least not to a high degree.

I can't even put into words how much I would love to do with one of my big Nikko F150s what has been done to theΒ Lunchbox but as the chassis and gearbox have some not insignificant differences, it will require a lot of variations. I would really love to make the rear suspension work on one of those trucks.Β 

It's really great that we can inspire each other like this.Β B)

Do it! I'm sureΒ  you'd find a way to get it done, take some photos, and measurements, and people would give ideas I'm sure.

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My lunchbox was stolen 1 or 2 Years ago.

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But since yesterday i have a new used one without any Mods.

I've ordered 2 Sets of Tamiya 50520 CVA Shocks and a Ball Bearing Set.

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But i'm not shure if i schoud use a 5th Shock, the Fishingline or the Pintopower Brace.....

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I do not want a 4 Link Setup.

The 5th Shock destroys the Plastic of the Gearbox.

The Fishingline, i cant imagine that it would be as good as a 5th Shock.

And the Ampro Brace is to expensive....

20 Bucks + 20 Bucks for Shipping to Austria.....

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On 10/5/2021 at 6:08 AM, whahooo said:

The Fishingline, i cant imagine that it would be as good as a 5th Shock.

Oddly enough, it is. If it is tied tight with the gearbox in the bottom of the mounting slots, it totally curbs upward movement on acceleration, but allows full articulation in all other aspects.

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Thanks for that opinion. Someone from an other forum has printed me some Braces for the Lunchbox.

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Should i send a Donation for the Idea to @Pintopower i don`t know how the rules are ^^

But i know it isn`t very gentlemenlike to "steal" ideas.

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So i inatalled a 3D Print Brace and CVA dampers with a Metal piston wirhout the holes.

If i had Plastic pistons iΒ would have installed the 3 Hole one....

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I think the Damper is damping to much resulting in a very slow Action.

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The Lunchbox lands good from heights of about 1 Meter, but it doesn't take the roughnes of the Ground very good.

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How much damping action should the rear Danpers have in your Opinion?

I tend to put in the softest oil.

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I tend to have little damping action in the rear of Β vehicles like the Lunch Box. There's a lot of unsprung weight in the back and the suspension has to react fairly quickly or bumps tend to shove the whole back of the truck up in the air.

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Thanks for your opinion.

Is there any Cheap Oil like Tamiya 200 (the red one) from another manufactuer?

Years ago i purchases a "soft" oil that was a lot slower than Tamiya Yellow, so i can't trust the Peopke at Conrad anymore....

I think the employee sold me 1/8 "soft" oil...

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I need that for my leaky Clodshocks (i will install orange O-rings) and my Lunchbox.

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