FWD/FF Buggy

[Origineelreclamebord]

Sorry, double post...

[Origineelreclamebord]

Thanks, I'm glad you like it!

The CAD/CAM modelling I find flexible to adjustments, and it's the portal to many manufacturing processes (such as 3D printing).

I'd love to get components manufactured to sell conversion kits, no doubt However, currently that's getting a bit ahead of things: Until I have actually built the second prototype and driven it a couple of times, I can't judge the status or in what stage of the project I am.

That's one of the reasons why I'm really eager to get the parts in and get the testing going a.s.a.p, but I can't make predications as to when that happens as I'm not in control of the manufacturing processes. Another reason is that I have set goals to drive the car on certain events.

[Origineelreclamebord]

I just noticed I'm missing a box to fill in the weight of the car, but... It's filled in! This is the setup I plan to use to test the car for the first time - unless it looks/feels really awkward on the pit table of course.

The main areas of focus are mentioned on the sheet. With one or two tests I'll find out soon enough whether my estimations on oil and springs are any good, whether I need the 'extra' degree of toe-in on the rear (compared to RWDs) and if a 4-rib tire has enough bite to keep the rear end from sliding out on corner entry. Also, I'm expecting the 4-gear setup to be quicker, but being familiar with the 3-gear setup already I see this as the best starting point.

These things are essential to determine for the car, and for a variety of surfaces: It's not guaranteed I'd want to drive either 3-gear or 4-gear all the time.

I'm really looking forward to checking the box on finding these big setup changes and starting to play around with all those spacers and the roll center of the car It feels a bit funny thinking of the setup for the car when the parts aren't even here yet, but let's hit the ground running when those parts arrive!

[Origineelreclamebord]

Build day is getting closer and closer. I was cleaning up and disassembling the first proto today to store it, when a guy from UPS turned up at my door with some precious goods!





Now all that's left to go is receiving the carbon platework - In the meantime I can think about the final colour for the printed parts: Keep them white, or paint them grey, black... perhaps even fluor orange?

[schmacher]

purple

[Losi_110]

I've just been reading through all the stages of this project and I've got to say this looks awesome I reeeaaly want a go lol. I take my hat off to you for sticking with it, it must take up a lot of your time. I'll wait with baited breath to see the build up of proto 2

[johnnygibbon]

The orange works for me dude

[tramp]

Awesome, i'd stick with Orange too, i was reading an article in this months rcracer magazine and it talks about dyeing plastic components, I'd have thought theses bits would be a good candidate

[GrahamH7060]

Lime green would look awesome !!

[Burty248]

I think the orange, carbon black and white combination would look best.

[cunawarit]

Originally Posted by GrahamH7060

Lime green would look awesome !!

I vote for that too! Green FTW!

[Origineelreclamebord]

Let this be a heads up to what will be posted on the forum soon... You will not be disappointed!

Just as a random and fun statistic by the way... The weight balance weight balance of 79/21* That's just 60mm behind the front axles, almost dead centre in the battery and 4% further to the front!

Another weight related fact... This thing is a featherweight! Without any weight added to the car, it weighs in at a mere 1284 grams!*

*Rolling chassis with Motor, Battery and Servo (No ESC, Receiver, PT).

[Origineelreclamebord]

http://www.oople.com/forums/showthread.php?p=777036

There we go That's the AC210FF For you! I just did a first test run with it on a brick road... DAMN THIS CAR HAS CHARACTER!

The car's acceleration I would say it isn't far off from an RWD bug. That's just the start though: I don't know how clearly I have mentioned the first prototype felt a bit lazy and had too big a turning radius, but this car is the opposite! The steering is more agressive than a Cheetah on a sugar rush! The turning radius is about as small as I have seen on a buggy of this size, I'm really baffled by the contrast from the last car.

I also found some things to work on. Off-power, the car becomes quite a handful: there is so little weight on the rear that it kind of starts to float at the back. Grip then becomes inconsistent and it easily tends to slide out to one side. This effect is even stronger under braking: The rear easily lifts up completely from the ground, and if that doesn't happen then you're left with a very loose rear end.

It should be an easy fix though It just needs ballast on the rear. A good thing, as there is limited space up front to bring the car up to the necessary 1474g to make it legal for racing. Also, I need to look into the rear tires: the side walls of these tires were covered in glue to prevent grip roll on carpet, so that might be part of the problem here. Lastly, this characteristic is something I also came across on the previous car on carpet and there I solved it only by increasing droop and using rear tires with more bite.

[mart3pop]

well done !! looking good

[Danny Harrison]

Looks really good, excellent work and craftsmanship there. It looks to have a very short wheelbase, could a slightly longer one help with the floaty rear end you think?

[Origineelreclamebord]

Thanks

I noticed exactly the same thing: it seems short! It's odd though... It's narrower than your usual 2WD (it's 240-242mm-ish), has a narrower chassis than your usual buggy and in fact with a 280mm wheelbase it's considerably longer than most wheelbase buggies come with as standard (though that recently shifted to +8mm for many cars). At 280mm it is 6mm shorter than the old one, and it may be part of the floaty rear end, but I think not the main cause.

I think it's this: With the weight balance and weight I measured the car has only 270 grams resting on the rear end when standing still Any increase and decrease of weight (=axle load) that happens on the rear end has a big effect on the percentage of grip on the rear end,even if the absolute weight shift is small. Off-power (=drag brake, 4%) and under braking this counts even more so because the braking removes even more axle load.

At that point any imperfection in the surface will make a huge difference for the stability. The smallest nudge will make it lose grip too far and slide because there is no weight to generate grip. Once you lose grip there is very little the car can do to activate it again because again there isn't any weight to play with.

All I need to do is make sure there is just enough axle load on the rear end under braking to keep the car from sliding to a point where you can't keep your racing line First thing here is to make it race legal. I have to add almost 15% of the current weight to the car. Let's assume that under braking the rear wheels also have 15% more weight to play with whatever was there under braking before... That could be the difference between spinning out and touching the apex like a pro. If that doesn't make enough of a difference I have a nice set of variables to play with:

- Use rear tires with more bite.
- Add more rear camber.
- Add more rear toe-in.
- Play with the ground clearance between front and rear.
- Use heavier front springs and damping (something that the car might need anyway).
- Add pack on the front (something it most definetely needs).
- Add droop to the rear (this I think should help particularly on bumpy surfaces, not to cure the rear bite issue itself alltogether).
- Add rear 'anti-squat' (spacers under rear suspension blocks).
- Add downforce on the rear end (after all downforce gradually goes down with the speed, it doesn't suddenly shift forward like the weight balance).
- Adjust the squat/kickup on the front.
- Increase the wheelbase (a realistic option as the car seems to have plenty of agility and the sliding has a bigger effect (and danger) at high speeds, but like I stated earlier on it's own maybe not enough).

I 'just' have to find out which of these variables makes the best difference Adding axle load is a thing that will happen just by making the car race legal... But reducing how much of that the rear end loses under braking is at least as interesting, as that mainly affects the car under braking (where the front end doesn't need that extra axle load from a shifting weight balance).

By the way, I'm just reminding myself... this was the first test with the car! I just threw a setup on there based on theories. I'm really happy with where the car stands with the first setup, with some adjustments I'm confident the car will have the immense steering and acceleration capabilities with a planted rear end.

[Origineelreclamebord]

Another update. I've made the following changes:

- 1.3mm x 4 Pistons on the front (instead of 1.3mm x 6).
- 1.4mm x 6 Pistons on the rear (instead of 1.2mm x 6).
- 2.81 lb/in Black rear spring (3,63 lb/in Dark Blue spring).
- 40g of weights on the rear end of the chassis plate.

I just weighed the car: it's 1455 grams now I've added the weights, ESC and receiver. I don't know exactly how much a PT and bodyshell would weigh, but all in all this means the car needs roughly 40g to become competition legal (probably 60g if your wiring is nice and short ). I had slight concerns before that I needed to add a lot of weight to the car... but 40-60g is a perfectly compact and noticable amount of weight to play with!

So with the setup changes, how does it go?

Well... Awesome! Ok, the rear end I would still call loose-ish, but now most slides are pretty controllable by countersteering, and of course driving style is a determining factor here. If you're agressive on the turn-in and brake by cornering, it will slide (a lot). when you idle or brake slightly so the weight isn't completely thrown on the outside front wheel on turn-in it remains nice and stable.

As the first track test is on clay, not on a high-bite surface, I think this is a reasonable starting point. Just to be sure, I will be trying out how the car responds onroad with tires, ground clearance and droop levels for clay. Also, I'll try one or two things that to try and make the rear end even more planted, so I know how to adjust the car in both directions if adjustments need to be made at the trackside

[RC-trix]

Likin'it Paul
Next i'd go for more rear toe to try and calm the rear even more.
Keep us posted how the printed material stands up.

Steven

[Phil Channon]

Really like the look your car.

I use to run a yokomo YRF2-SP and found the best way to keep the rear under control was

. Increase the rear toe-in
. Set up ESC to always have power to the wheels. You will only need a small amount to help the cars stability
. Run the softest tyres possible

Looking forward to further updates.

[Origineelreclamebord]

@RC-Trix: Funny you mention it, I've just tried more toe-in! I must admit, not with the way I intended to adjust rear toe, but this works pretty efficiently!

The added rear toe-in seems to help slightly, even with higher ride height and more droop (that, to my understanding, should exaggerate the weight transfer into corners that causes the sliding in the first place).

Also, I think I'm getting the hang of it now, it takes some getting used to the car. On tarmac, the last car had a very stable rear end - I suppose thanks to the wider tires - but it's loss of rear traction seemed more snappy. So overall you needed to use all the steering it had and in every once in a while it'd slide... considerably!

With this car there is less rear traction to start with, but it's less snappy. That combined with the lively front end I guess it just requires a more subtle touch to the steering That said, of course I'll be looking to find a way to make the rear end more planted: I haven't driven it on a bumpy surface, but there it may need the extra rear bite to deliver consistent lap times.

@Phil Channon: Thanks for the advice! Do you recall how much toe-in you were usually running or how much you added?

Cool you mention the ESC set up. I found out on the last drive if I ease off the throttle instead of let go of the throttle suddenly, it stays entirely stable... as if it needs a smoother weight transfer.

The soft tires I'm definetely going for then! I have a set of Proline M4 Calibers (4WD front and rear) and these I'll definetely glue these to compare them with M3 Caliber/M3 4-rib tires (and combinations/hybrids of the two).