Lunchbox Issues!

[pearce_jj]

Hi all! Just joined this board and hopefully some of you guys and girls can help me out. Sorry for any repetition, so here goes....

Recently got myself an RR Lunchbox - always wanted one originally.

Built it with bearings, sport-tuned (black) motor, lights, chrome wheels, and aluminium body mounts. Recently changed spring-to-arm linkages at the front with aluminium versions as one of the plastic ones had sheered.

Questions!

Firstly yet another crash (:-() broke the servo saver. Local model shop advised changing Acoms to Futaba S3003 with a trickbits TB3002 saver on it. So hopefully that will be better, any comments?

Secondly the two weedy 'axle springs' (positioned just behind the battery) have completely disintegrated - suprised as it's probably only been run 10 full charges. I'd like to get rid of that audible transmission 'knocking' the car suffers from as well but keep the v.long wheelies - so any ideas on how to revise this part of the car greatly appreciated!

Thinking along the lines of somehow mounting rubber gromits in the slot either side of the transmission arm, allowing a more restricted movement but cushioned. If the full movement is required I could probably get some replacement links made up in (more!) aluminium with a longer slot I suppose?

Thanks all

James.

[blakeatron]

if you do a quick search for the - extra shock mod. basically it envolves installing a 3rd shock at the rear - which removes the use of the stupid springs.

as for the servo, any main brand should do as the steering isn't that heavy on the lunchbox, as for the servo saver ive always used the stock in mine and it hasn't bust - yet!

[pearce_jj]

if you do a quick search for the - extra shock mod. basically it envolves installing a 3rd shock at the rear - which removes the use of the stupid springs.

Hi, thanks for taken the time to reply.

Although I like the idea of the 3rd shock mod, I can't see that this is going to get rid of that 'knocking' noise? Also is the top of the chasis strong enough to avoid cracking it?

[mymonsterbeetleisbroken]

Although I like the idea of the 3rd shock mod, I can't see that this is going to get rid of that 'knocking' noise? Also is the top of the chasis strong enough to avoid cracking it?

Welcome to the site!

The 3rd shock mod is the most widely used home made mod for the lunchbox/midnight pumpkin chassis. It most certainly gets rid of that knocking sound, and stops your motor hitting the right hand rear shock absorber. I have a 19 turn motor in my truck and not even that can cause a knocking noise, as i've got a CVA shock damping the movement of the gearbox

Here's a few pics:

As you can see, I've also braced the rear deck of the chassis to make it rock solid. They can crack but it takes some nasty crashes to do so.

More pics here!

There's no other durable way to sort out the knocking, and all you'll need is a CVA shock, an extra metal shock mount bracket, a junior hacksaw and a needle file. The shock attaches to the gearbox through the metal rod that runs through the pivoting part. Just remove part of the gearcase (with hacksaws, dremel etc..) to expose the metal rod and attach the shock. The shock attaches to the chassis using a standard metal shock bracket (the lunchbox should come with 4 extra of those). All you need to do is drill a small hole and mount it with a nut and bolt.

Use a fairly hard spring and medium shock oil in the 3rd shock. This will provide perfect damping to the gearbox and seriously improve your truck!

[pearce_jj]

The 3rd shock mod is the most widely used home made mod for the lunchbox/midnight pumpkin chassis. It most certainly gets rid of that knocking sound, and stops your motor hitting the right hand rear shock absorber.

Hi, thank you for replying with such detailed explanation!

There seem to be a whole load of different types and lengths of shocks, would these do:

http://cgi.ebay.co.uk/ANSMANN-RACING-PK4-O...1QQcmdZViewItem?

Did you bother with the original axel springs at all?

[mymonsterbeetleisbroken]

I've got a shock from the tamiya short damper unit set on mine, those are the same shocks that came with the monster beetle, and are also the recommended upgrade for the lunchbox.

Those Ansmann ones should be ok for the job, though they are quite a bit shorter than the shock i've put on my truck. I've seen others use a touring car shock so they should work

I got my truck years ago off a friend. It was run for years in stock form and i didn't even know what the left overs of the axle springs were for! (back then there was no tamiyaclub and i had no instruction manual )

[pearce_jj]

Brilliant, thanks!

DF02 shocks the same size? http://cgi.ebay.co.uk/Tamiya-DF-02-Oil-Sho...VQQcmdZViewItem

With the 3rd shock can the rear wheels still move up and down vaguely independently?

[mymonsterbeetleisbroken]

Those should do the job

You'll still get perfect articulation of the rear suspension, as the 3rd shock mounts in the center of the gearbox it doesn't compress much when the axle articulates.

[pearce_jj]

Thank you for the help, it is greatly appreciated.

Is there a gear set with no diff for the LB? Managed to get some good doughnuts going today but need the diff locked really :-)

[skip665]

Use some polymorph - I have locked my Mud Blaster gearbox with this stuff and its excellent! Completely reversible procedure too!

http://cgi.ebay.co.uk/Polymorph-Low-temp-m...1QQcmdZViewItem

[mymonsterbeetleisbroken]

Dont forget that if you lock the diff all you'll be able to do is wheelie and do doughnuts

It'll roll over easier and steering will be less than useful

should be fun though!

[pearce_jj]

Dont forget that if you lock the diff all you'll be able to do is wheelie and do doughnuts

It'll roll over easier and steering will be less than useful

should be fun though!

Hmm - will it be that bad? Don't remember my brat being awful, admitedly that was a log time ago though.

What I really need is a limited slip diff....

[blakeatron]

Hmm - will it be that bad? Don't remember my brat being awful, admitedly that was a log time ago though.

What I really need is a limited slip diff....

im sure someone made a slip diff with putty and oil - not sure on what and how much tho!

[billg4]

the diff is fairly open so any putty eventually gets thrown away from the gears and your back to open all over again

[pearce_jj]

the diff is fairly open so any putty eventually gets thrown away from the gears and your back to open all over again

Will any of the tamiya ball diffs fit? And if so, will they be firm enough to doughnut?

[mymonsterbeetleisbroken]

Will any of the tamiya ball diffs fit? And if so, will they be firm enough to doughnut?

Nope i dont think so, if there was i'd like to know about it! There were ball diffs for clod busters years ago, which may have been usable if you messed about, (you'd have to really mess about lol) but just about every other diff you find is much smaller then the big diff tamiya used in the lunchbox style gearbox.

Not sure if a solid after market clod buster diff could be modified to fit, i can't remember if the number of teeth are the same on them.

Something solid like JB weld would stay in there. Anything that sets hard should lock the diff up.

[markbt73]

DISCLAIMER: This is just an idea; I haven't actually tried it yet.

What if you replaced the little spacer tube on one side of the diff with a really stiff spring? If you made it the right length to just put a little pressure between the gears, tht should slow down the diff action a little bit. The diff would still unload in turns on hard surfaces, but it would be a little "notchy" and it might keep it from unloading on dusty surfaces enough to get some good donuts in.

Again, jut an idea, but I might have to try it myself...

[pearce_jj]

some good ideas there gents, thanks for the replies!

So if the ball diffs are smaller, maybe could hack a lunchbox diff wheel to fit another diff within, holding the lot together with that cold-setting plastic stuff? Then what about attachement of the drive shafts though?

[mymonsterbeetleisbroken]

DISCLAIMER: This is just an idea; I haven't actually tried it yet.

What if you replaced the little spacer tube on one side of the diff with a really stiff spring? If you made it the right length to just put a little pressure between the gears, tht should slow down the diff action a little bit. The diff would still unload in turns on hard surfaces, but it would be a little "notchy" and it might keep it from unloading on dusty surfaces enough to get some good donuts in.

Again, jut an idea, but I might have to try it myself...

Thats a neat idea and really needs to be tried out by someone

I think the spring would also provide resistance to the hole drive train though as it will be forcing the diff over to one side of the gearbox. You'd have to somehow take material off the inside of the diff though as those diffs don't get "notchy" when compressed.

[markbt73]

Thats a neat idea and really needs to be tried out by someone

I think the spring would also provide resistance to the hole drive train though as it will be forcing the diff over to one side of the gearbox. You'd have to somehow take material off the inside of the diff though as those diffs don't get "notchy" when compressed.

Yeah, you'd have to keep it from rubbing on the insides of the gearbox... thrust bearing and cone washers maybe? It would still cause heavy side loads on the axle bearings and wear them out quicker... unless you put a thrust bearing on each side?

And it occurs to me you're right; the step in that little center shaft in the diff will keep the large bevel gears from being pushed too far in. You'd have to cut that step down to give it some room to compress.

Now I wanna go tinker and see what I can come up with. Too bad I'm stuck at work.

[pearce_jj]

Evening gents!

Re the spring diff idea, perhaps a spring each side is the answer to eliminate the sideways forces?

Anyway back to the 3rd shock mod, I have another question! Just received a full set of DF02 shocks, so two long and two short.

Questions:

- Would it be better to use a short shock, with horizontally mounted bracket on the chasis, or the longer shock directly into the top plate?

- Preumably a hard setting is required?

- Would a lunchbox with two oil shocks (say the back) and two friction shocks be rediculous? I like the bouncy unpredicable handling so I suppose I've answered my own question!

Cheers!

[mymonsterbeetleisbroken]

Let us know how you get on with it

[pearce_jj]

Evening Chaps

Thanks for the help with the 3rd rear shock mod! Absolutely brilliant, has made the model so much better. Plus can pull very, very long wheelies with a bit of car on the throttle now!

Here's a couple of piccies:

[mymonsterbeetleisbroken]

That looks spot on, excellent job

[pearce_jj]

That looks spot on, excellent job

Thanks MMBIB - and for your help of course