Jump to content
Saito2

Lunch Box rear suspension... that old chestnut

Recommended Posts

Has anyone found a good spot to tie off the fishing line to the chassis on the lunch box? 

Share this post


Link to post
Share on other sites
7 hours ago, jellon said:

Has anyone found a good spot to tie off the fishing line to the chassis on the lunch box? 

Hi you can just make 2 small holes in the chassis to tie the string through like in the position you mount the 3rd shock in.... and remember when you tighten the line only tighten it a bit so it don't start compressing the rear shocks...you want it to move nice a freely. 

  • Thanks 1

Share this post


Link to post
Share on other sites
On 6/20/2020 at 3:16 AM, shenlonco said:

Hi here is how it works as shown in my video.

And this shows all lunch box mods and the string mod on the lunch box... but the above video I explain how it works and how to do the mod better.

 

Thanks shenlonco. I've tried the fishing line and rubber tube suspension mods tonight. 

I do like these free mods!

In the absence of a thing called 'shoe goo' in the UK.... I've used some wader repair glue, called stormsure to secure the screw and the rubber tubes.

I'll let you know how she runs.

 

20200624_214557-COLLAGE.jpg

  • Like 1

Share this post


Link to post
Share on other sites

I've also used a 'fantastic elastic' glue from 'Poundland' - and guess what - it's a pound  :lol: , - not all is a pound these days in Poundland - it could be more so beware people - it's a jungle out there

  • Haha 3

Share this post


Link to post
Share on other sites
4 hours ago, jellon said:

Thanks shenlonco. I've tried the fishing line and rubber tube suspension mods tonight. 

I do like these free mods!

In the absence of a thing called 'shoe goo' in the UK.... I've used some wader repair glue, called stormsure to secure the screw and the rubber tubes.

I'll let you know how she runs.

 

20200624_214557-COLLAGE.jpg

:DCOOL!!

  • Like 1

Share this post


Link to post
Share on other sites

Beauty :D. Runs much better now, no clunking, softer landing and a bit more traction at the front. The front wheels sit right now too.

It's still bonkers.... but a bit more refined. 

I actually left the tubing on the shocks adrift in the end, as it was stopping the shocks sliding back in to place (too tight). This way they sit at the top and just act as dampers. Seems to work just as well.

Thanks again @shenlonco I definitely recommend this easy, free mod.

IMG_20200625_205617612~2.jpg

  • Like 1

Share this post


Link to post
Share on other sites
7 hours ago, jellon said:

Beauty :D. Runs much better now, no clunking, softer landing and a bit more traction at the front. The front wheels sit right now too.

It's still bonkers.... but a bit more refined. 

I actually left the tubing on the shocks adrift in the end, as it was stopping the shocks sliding back in to place (too tight). This way they sit at the top and just act as dampers. Seems to work just as well.

Thanks again @shenlonco I definitely recommend this easy, free mod.

IMG_20200625_205617612~2.jpg

That's great! I CA glue the rubber on to the chassis and I use some light grease on the shock shafts and it makes them work kind of like oil filled shocks.

  • Like 1

Share this post


Link to post
Share on other sites

@shenlonco could you give a bit more detail on the cheap engine upgrade for lunchbox. The tamiya sport tuned is a bit pricey. I'm in the UK. Thanks

Share this post


Link to post
Share on other sites
9 hours ago, jellon said:

@shenlonco could you give a bit more detail on the cheap engine upgrade for lunchbox. The tamiya sport tuned is a bit pricey. I'm in the UK. Thanks

Hi you can get a cheap RC4wd 20 turn crawler motor.

  • Thanks 2

Share this post


Link to post
Share on other sites

I've had a little breakthrough guys. Been thinking about this for a while now. The 4 link helped a lot but still very little weight working on the back suspension. One way to improve that is to move the dampers further toward the chassis to get a better leverage so I had a go at mounting shocks as far forward on the actual lower links as I could get.

This is all very crude prototype stuff but I think the video speaks for itself. Doing this drop test before, even with the 4 link, resulted in very little suspension movement and the rear end bouncing back up into the air like a ball.

Take a look at this:
 

Look at the suspension move! Amazing difference. And the travel is massively improved too because the shocks don't need to move as much when they are that far inward for a given amount of movement at the wheels. You can push the rear down so much further now without the shocks bottoming out.

Like I say, very early days. Dampers are probably too long if anything, springs too soft (what a wonderful problem to have with a lunchbox!) various other stuff needs to be done but wow what a difference already!

Did I mention I haven't even put OIL in those dampers yet!!?!?!

Stay tuned.

  • Like 7
  • Thanks 1

Share this post


Link to post
Share on other sites

That looks great , nice work . I recently transplanted a Kyosho Ultima rear end to a Lunchie , the shocks are in the same position as yours , it works so much better than stock

  • Like 1

Share this post


Link to post
Share on other sites

@nowinaminute That's really cool! The nice thing now is that if it feels too soft as is all you need to do is move the bottom of the rear shock rearward on the link slightly. Tune by the leverage rather than changing the shock. Looks great. 

  • Like 1

Share this post


Link to post
Share on other sites
4 hours ago, ThunderDragonCy said:

@nowinaminute That's really cool! The nice thing now is that if it feels too soft as is all you need to do is move the bottom of the rear shock rearward on the link slightly. Tune by the leverage rather than changing the shock. Looks great. 

Yup I can just move it back and forth to tune it. Needs more tinkering but initial results are promising. It will never rival a decent wishbone setup but it's interesting to try and take the solid axle as far as it can go and this is a big step again like the initial step to 4 link.

  • Like 1

Share this post


Link to post
Share on other sites
18 hours ago, KEV THE REV said:

That looks great , nice work . I recently transplanted a Kyosho Ultima rear end to a Lunchie , the shocks are in the same position as yours , it works so much better than stock

Yeah I saw that it looks cool! I've wanted to try that for ages too. I have another Lunchbox I might try something like that on but with this one, I wanted to just try and see how much I could squeeze out of the old solid axle.

  • Like 1

Share this post


Link to post
Share on other sites

Took it for a bit of a test today. Still needs work but wow, never seen the axle move around so much and respond to the terrain so well. Seems like the old suspension setup was holding the 4 link system back!

I still need to find stiffer springs. I tried mounting the bottom of the shocks further out but it barley made a dent. Luckily I had 4 of the shocks so I was able to take the springs from the other two and mount them externally so each shock now has a spring inside and one outside. Even with double springs though, they are a tiny bit too soft. I don't want to go too much further though because I don't want to spoil the amazing responsiveness I'm getting. The rear end sags a bit under power but there's so much more articulation on offer compared to before that it doesn't really matter as it still has loads of upstroke left even when it's sagging.

I need the skinny internal spring type ones to clear the suspension links but they tend to be optimised for crawlers so the springs are usually soft. There are some that come with 3 different rates of spring though so that might be something to try.

Turns out mounting the shocks so far inwards also makes the damping effectively softer so the typical 400cst wasnt even close to cutting it! I currently have 3000cst but I think 5000 might be more suitable. 

Anyways, all those issues aside, it's working very well at this point in terms of hugging the terrain. The more I drove it today the more I realised just how much I could get away with. This culminated in me giving it a torture test at the abandoned rugby pitch. A lot of areas here are populated with dozens of parallel ridges where people have gone back and forth in dirt bikes. I usually have to avoid these parts as even when I added 4 link, the Lunchbox would end up on it's roof.

Take a look at the video and see how busy that rear axle is. It's hard to appreciate just how bumpy that surface is without being there but hopefully you can see how free moving the rear suspension is. Normally the entire chassis and body would be bouncing up and down over the bumps but now the suspension does a good job of absorbing the worst of it. I never thought it would be drivable over these ruts and ridges!
 

 

  • Like 4

Share this post


Link to post
Share on other sites

And on slightly less ridiculous terrain, it was better than ever!
 


It even lands jumps better now with the rear end less prone to bouncing into the stratosphere with every landing. Hopefully it will be better still with some thicker damper oil. I don't think it will ever be great at larger jumps because it still has all that unsprung mass but it's certainly better at the smaller stuff, even things like dropping of kerbs is different to how it was before.

So still some refining needed but it already works great! 
 

  • Like 6

Share this post


Link to post
Share on other sites

Very nice work, and of course a lovely Tandy Off Roader body there too.

I added a 5th shock mod to by QD Pumpkin, which has a very similar geometry to the full size car. Simple spring with just enough pressure to keep the front end of the gearbox down on acceleration. With just spring shocks the whole thing is a bouncy mess, but at least I don't have to worry about that clicking and shuddering on throttle.

 

Share this post


Link to post
Share on other sites
3 hours ago, Nikko85 said:

a lovely Tandy Off Roader body there too

I've got one of those trucks . I converted it to run with an ESC as it didn't work with the old PCB .

Share this post


Link to post
Share on other sites

Are there any details of the parts you used on this rear end , or can you show the actual parts you used  . I'm keen to try this on an LB :)

Share this post


Link to post
Share on other sites
4 hours ago, KEV THE REV said:

Are there any details of the parts you used on this rear end , or can you show the actual parts you used  . I'm keen to try this on an LB :)

I can show you the basic design. A fellow member helped me design it, or rather he designed it and I offered some rudimentary input. Only problem is I haven't heard from him in almost 3 years and he was last active on the site in August 2019 I think. No idea what happened to him, hopefully he is ok.

I can't really be giving the STL files away without his blessing, that's the only problem. But anyone who's got some 3d modelling skills should be able to look at it and approximate the setup. I would do it myself but I am only really capable of making very basic stuff on tinkercad, complex shapes and filleting and chamfering etc are all beyond me, unfortunately. 

Our contact stopped in it's tracks so abruptly that the design never even got finalised. He didn't even have a Lunchbox at the time so all the geometry etc was essentially guesswork. There is still a design flaw on the chassis mounts too in that they don't connect to the battery tray like the stock parts do, I had to kind of improvise a solution with some of the metal U shaped brackets Tamiya make. Also the damper is a little too close to the motor but this didn't effect me as I switched to a little brushless outrunner.

Alas, this is the basic setup. A mount around the gearbox made of 3 parts and then 2 mounts on the chassis that replace the pivots/mounts on the stock setup. Then just 4 links made from threaded rod and ball joints. This gives you a triangulated 4 link setup which stops the suspension locking up under throttle and allows better rotational articulation of the axle too. The entire axle is mounted backwards too so that there's more room to work with.

LB 4 Bar iso.JPG

LB 4 Bar side.JPG



The next step was simply removing the dampers from the default position and mounting new ones directly onto the upper suspension links. The tops of the dampers are simply bolted onto the rear bulkhead. I will be adding a little metal mending plate or similar at some point to strengthen that area.

  • Like 3

Share this post


Link to post
Share on other sites

Happy to offer any help I can or collaborate towards a fully realised version any time. That offer is open to everyone :)

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...