Bump rubbers.

[PaulC]

From my PC and Play Station racing sim days and my Tamiya buggy I remember there being adjustable "bump rubbers".

Basically if you push your buggy/truck into the ground if the chassis can actually touch the ground the suspension is set wrong.

Now, my Ansmann is like this and the bashing videos on you tube show it slamming into the ground off jumps. I've heard that CRACK on many videos of many different buggies.

Slamming the hard unsprung chassis into the deck will not help it or your engine/radio gear any good at all! That is what suspension is for!

On the Tamiya there were little arms on the suspension that collided with little rubber tipped grub screws which could be adjusted out or in and the idea was to set them so that the rubber stopped the suspension travel just before the chassis hit the deck.

My current buggy has no such device that I can find and the suspension travel is enough for all 4 wheels to be ABOVE the chassis plate by 1/4 inch.

What do you think about this for a solution - and how I believe the did it in the old days of F1 cars.

Put a piece of fuel tubing over your shock shaft. Cut it just long enough that the fuel tubing starts to restrict the shocks compression with about 1/2 inch of ride height. The fuel tubing, as it compresses, will become exponentially stiffer so that pushing the buggy down until the chassis hits the deck will be exceedingly hard.

Next time it goes off a jump the shocks compress, then the fuel tube compresses and the chassis doesn't contact the deck.

I haven't tried it yet, but can't see any reason why it won't work. Any thoughts?

Paul

 

[robmob]

Fuel tubing on the shafts is the easiest way to do it.

If you want to lower your ride height, one way to do it is to put the fuel tubing on the shaft under the piston inside the shock body.

 

[2revo1maxx]

I think the companies don't do that anymore because people are going to jump over their house and no rubber baby buggy bumpers are going to help ya there. Just my opinion, and I can remember a time when suspension did all the work, but I think the chassis hitting the ground is really no big deal with today's electronics and plastics.

 

[PaulC]

I think the companies don't do that anymore because people are going to jump over their house and no rubber baby buggy bumpers are going to help ya there. Just my opinion, and I can remember a time when suspension did all the work, but I think the chassis hitting the ground is really no big deal with today's electronics and plastics.

Of course they want you to smash it into the deck! They make money when you buy parts

 

[Extreme RC Mods]

Racing and bashing has come a long ways over the years, jumps are bigger and bashing is extreme. Adding any type of springy material to stop the slap will drastically affect the handling of most RC's, they will become bouncy and other parts will likely be damaged. Adding thicker shock oil can help but it takes away from the handling as well. If you try to stop your chassis from hitting the ground, chances are other parts of your suspension will fail as they are not designed to take the added stress.

 

[drdoom405]

Carefull with the fuel tubing on the shock shafts. Last time I tried that I ended up with 5 bent shock shafts.....(out of 8 on a maxx)

 

[neobart]

If you start setting your suspension up so the chassis never hits the ground, you will start breaking shocks, arms, axles, towers etc..........These cars take jumps that are way bigger than their scale, so any idea of how suspension works in 1/1 cars can not be translated directly.

 

[PaulC]

Scale is complicated when it comes to comparing things like jump heights.

Yes the car is 1/8th the size of it's real counterparts and it seems logical to say that if the scale car lands from 6 foot up that is a scale height of 6*8 = 48 feet and probably way too much for the real sized car.

However.... if you drop the real car and the scale car from the same height they will - excluding air resistance for now - hit the ground at the same time and the same speed, be that height 6 foot or 60 foot.

The kinetic energy that has to be dispersed by the suspension is only then relative to the mass of the car. 1/2 MV(sqr). As we know that the V is the same we only need to look at M and the scale weights.

My buggy weighs about 3 kg. So that is a scale weight of 3*8*8*8 = 1536kg. Which is probably about twice the weight of the real car.

So in that sense it seems like the suspension in a 1/8th scale buggy has to work twice as hard and you are right. I'm not so sure though. If you look at the suspension on a 1/8th scale buggy and imagine it full size, would the shocks be that big in relation to the car? Would the towers, suspension arms, linkages be that thick?

 

[neobart]

There's a lot more to this scale stuff than I can wrap my head around. Gravity is one thing that scales very badly. Fact is that compared to the size these RC cars see the same abuse as a Baja truck.

Fluid dynamics don't scale to well I would imagine, so the shocks need to be bigger relative to the size of the truck for the silicone oils to work at their best.

Just a few thoughts of mine. I could be dead wrong however.