FWD/FF Buggy

[Origineelreclamebord]

Update time!

I drove the car on saturday... Wow! The car seemed ok: Better damping/spring setup, quicker with the more powerful motor - eventually anyway The car had loads and loads of wheelspin. Also, it seemed to understeer the same or more as the first test - back then I didn't get the chance to push it, so that might contribute to that.

I got a set of 4WD front Proline Caliber tires (with a cut profile) mounted on rear wheels from one of the fellow drivers and I put it on the front end. The understeer was reduced considerably and the car seemed like it had a better aid to put the power down, too. It could be down to the narrower tires. Also, the tires seemed to balloon less. My theory: this may help in the corners, where the inside tire tends to balloon a lot, pushing the car into sort of a roll and losing a lot of drive on the outside wheel.

Another big thing I found out... It's durable enough to jump, and it was very manageable to jump it. In fact, I think this car flew easier and was easier to adjust in the air than my TRF201 was with that (sensorless) motor fitted! I was expecting a tendency to do nose-dives, but it seems the car is pretty stable in flight and can even be flown with the front end as the highest point of the car

I wanted to film and photograph the car, so I asked a good driver to try it out. He showed it was easy to adjust the roll in flight as well - for him anyway, I don't trust myself with trying that sort of stuff

During the testing day I spoke with a lot of drivers about the car and got some great advice. In combination with the test day I got a good list of revisions for this car alone:

1. Do away with the 'swept' driveshafts.
2. Reduce the kickup as far as possible.
3. Revise the front shock system (rocker arms, rocker arm position, deflection/movement of the rocker arm, front shocks perhaps)
4. Add more droop to the front suspension.

Here are some pictures of the car, in and after action:




















It's just one of the 150+ pictures - and I also have 3 videos. So... you can expect a compilation of that soon! While I'm working on that, enjoy the pictures!

Edit: Videos:
http://www.youtube.com/watch?v=f2QPP6eNQKo
http://www.youtube.com/watch?v=iaKl5jOdzxQ&

[johnnygibbon]

smaller wheels like 2wd fronts on the rear axles should help understeer
it did with the maxxum - less grip i prsume
still looks awsome
and it flys !!!!!!!

[Origineelreclamebord]

Thanks for the advice Narrow wheels and tires would be preferable on the rear, even if were only for less mass on the rear. I see why lower grip rear tires might work, so it's definetely something to test! BRCA regulations don't allow it right now to use narrow wheels, hence why it runs wide rear tires.

I'm sure though that there are things to try out to reduce grip: different compounds, other profile tires, the use of different or no inserts, and of course these options should be tested against using narrow rear tires. Not to mention that a similar test should be done on the front. I guess that will happen somewhere in it's development - I can't exactly say when, but it's good to test the car on the different rubber people might run the car with.

[mro_racing aka Doorbell]

try a tight diff if your looking to have more front end on power

[Benh]

Would it be possible to manipulate the inserts in the rears to try and reduce the contact patch. Might end up quite firm in the centre but might be enough to get the result without breaking the rules?

[mrspeedy]

A couple more things to add to your list of things to try ...

Trim out that huge rear wing, I'd get rid of pretty much all the back section of it so you lust have the flat plane and the end plates ...... and how about bald rear tyres if you want less rear grip .... oh and a geared diff if possible ?

[Origineelreclamebord]

Thanks for the advice guys

Re the diff options: The ball diff can be tightened by 1/4 to 1/2 - I'm not sure though that's a good idea with steel balls. It's noted though, I'll try that.

I also want to try a gear diff - sooner or later. It would be interesting to see what the different construction does to the forward traction - and if with the thick oils you can find better forward traction without making the car understeer too much.

As for the rear tires: there are so many things to try out - I could use stiff inserts, completely rigid inserts, glue the majority of the width straight to the rim and use only a small ring of the actual tire as a contact patch... In the end though, it's also about finding solutions that are easy to use as well as within the rules. I think playing with inserts and the tiretread would be the best options.

Lastly, the wing. Now I know it jumps stable (with this wing), I can start looking at the affects of running (and flying) it with less or no rear downforce

[Hpi_guy]

What about predator style and use a front wing

[Origineelreclamebord]

It could work, yeah It's already got some kind of cab forward story going on at the front, and I suppose more front downforce can't hurt performance. I'm not looking to make a 2008 F1 style car though:



It's as if they used the amount of 'aero' stuff on the car as a cloaking device for the technology that made the car go fast

[Origineelreclamebord]

Update Time:

OLD


NEW


Do you spot all the differences?

It's new geometry for the rocker arm system up front. In the last test I was made aware that the rocker arms were hitting extreme angles - causing a lot of forces to be applied onto the axle of the rocker arm, and not actually into the rotation (=into the damper). This may make the suspension less consistent - and it sure will compromise it's durability.

Also, it turned out that the car had less droop on the front end in practice than in the CAD model - in fact the droop of the car was quite low (only a few millimeters really). The new system allows for a lot of droop, so much that I'll probably be running internal shock limiters At least then I'll be able to adjust the droop accordingly.

On the 11th of November I'll have my next racing event - I will take the car with me next to my TRF201 - and I'll probably be driving this car or the TRF201 in the 4WD class (it's a club race, so it's not a big deal) so I can get the most from the few events I'll be able to visit this winter I hope I'll have the new parts in by then, it promises to be a lot of fun!

[dodgydiy]

4wd front tyres were definately better on the maxxum when i had it, although they were on the narrow front wheels, not the rears as you ran them. they gave more consistent steering and more traction, i would say it is probably the more weight on a smaller area helping them to bite in better. if you do try a geared diff, dont go too heavy on the oil it may help with traction but will take away quite a bit of the off power steering, tried mugen diff grease which was like treacle in the maxxum and it was awful. much better with standard lm grease

[Origineelreclamebord]

Cool, thanks for the advice I do need to find out how much it was the tire width that contributed to the grip, and how much the cut tire profile - I used a similar cut profile on the rear of my TRF201 and the increase in bite (mainly forward traction) was huge! Perhaps I can make drive wide uncut vs. wide cut tires to get an impression of the differences just that gives.

As for the diff, I'll keep it in mind if I try it out. To be honest though, so far on all test runs I don't recall a lot of off-power running To be serious though, I really can't use less off-power steering: It's already a bit pushy turning into corners.

[johnnygibbon]

i also found 4wd fronts best and i would recomend trying differant wheels and tyres on the back it massivley affectedsterring and hadeling on my maxxum
and as for the diff i say lock it and boot it
fwd is all on power steering
keep em coming dude

[Mike2222]

Builders of front wheel drive cars may be interested in the BRCA tyre rule change at the last AGM. Control tyres on 2wd cars are now on the driven axle, not necessarily the rear axle. The other axle tyers are free choice. (1/10th off-road section rule 23.11)

[Origineelreclamebord]

Originally Posted by Mike2222

Builders of front wheel drive cars may be interested in the BRCA tyre rule change at the last AGM. Control tyres on 2wd cars are now on the driven axle, not necessarily the rear axle. The other axle tyers are free choice. (1/10th off-road section rule 23.11)

Thanks for the post It's an important change for this project - it might be a slight disadvantage for getting the optimal forward traction, but of course it does mean the car's rear suspension can become lighter!

[martin_lawson]

Love the design! I converted an original Couger to FWD years ago, everyone laughed when I turned up at a club meet with it until I was beetling them all!!
Also built a mid motored 2WD in the mid 90's, made me laugh when I returned to off road to find that was now the norm.

Great to see someone thinking out of the box!
Wish I had the time to scratch build cars again.

Keep up the good work!

Martin

[Origineelreclamebord]

Sounds very nice Martin Do you have any pictures of the FWD Buggy that you could share?

Speaking of pictures... The buggy has made it's international introduction at the EOS in Langenfeld

Unfortunately it wasn't for racing purposes... It was my first time to drive on carpet, the track was quite unforgiving (the jumps demanded you to get into their 'flow' - which I found very difficult) and I run the hardest spring setup I have - which is a decent setup for dirt and clay - so I couldn't really set up the car for the track.

That didn't stop me from running the car though... A bit on (wet) astroturf outside (which went quite well with the setup+Schumacher Full spikes up front), and a brief run on saturday on carpet (after all the heats, and running Schumacher Mini pins up front).

The result? Huge forward traction without wheelies! (Try that on full power you RWDs!) I think when driven well an RWD can still beat it's forward traction, but the difference should not be nearly as pronounced - I was surprised and very impressed by that!

However, it wasn't all fun. I couldn't properly brake before corners: The car braked strong enough to make stoppies, and even if you didn't do that, on turn-in the rear end would just break out. I did manage to keep the front end at the front a few times - this resulted in a stable car (as long as I didn't decelerate) with seemingly less understeer than on dirt.

I think to get it really working on carpet it needs a stiffer front end for these high-bite conditions, increase rear droop and decrease front droop - and if that doesn't work... weight on the rear I'd do a lot to prevent that though, the forward traction was unreal and I want to keep it that way!

[cryer-evo]

this car looks sweet mate are you ever going to put it into production ?

[Origineelreclamebord]

Originally Posted by cryer-evo

this car looks sweet mate are you ever going to put it into production ?

That's the ultimate goal of course! However, 'production' is very relative. It will be hard to create high demand for a car like this - it'll have to prove itself through performance to even make a chance to appeal to the masses.

So if the car becomes good enough to sell conversions of it will be a challenge getting the conversion affordable without compromising the design... First I need to get to that stage though where the design leaves RWDs eating dust (and/or shredded bits of carpet)...

[Origineelreclamebord]

Ok, update time! I implemented a few revisions







I decided to give the car a new gearbox, new chassis layout, upright shocks, new suspension geometry and eh... I think I didn't mention it's just a new design from the ground up?

To get into it in a bit more detail, these are the main features/changes:
1. DEX210 Gearbox (To allow 3 vs. 4-Gear and Ball vs. Gear diff testing).
2. Team Durango as main supplier of donor parts (I hope this speaks for itself when I'm using a Durango gearbox).
3. Upright shock layout (To focus on just one oddball feature on the car at a time and make the car easier to understand and improve on - I'd love to return inboard suspension back in the equation when I have gathered enough knowledge on FWD).
4. Driveshafts in line with outdrives (To reduce drive inconsistency due to large angles of the driveshafts in steering and suspension movement).
5. Shorty LiPo across width of chassis (pushing the weight balance further forward, allowing a more compact chassis layout).
6. New chassis layout (This time around taking into acount it has to have room to carry a certain size of electronics whilst keeping it as narrow and compact as possible of course).
7. Updated Ackermann and Bump-Steer Geometry (it is to be tweaked somewhat more, but this time around at least not just the inside wheel will steer And bump-steer is next to zero).
8. Reducing anti-squat/kickup to zero (the current proto had better forward traction when I minimized the anti-squat).
9. Less Parts! (For obvious reasons... Quicker to build, easier and more fun to work on, cheaper to manufacture, and if all goes well just as durable).

I'm quite chuffed with the design. I started only a very short while ago making the first parts, and most things came together without too many problems.

There is only one BIG problem I have to overcome. The length of the DEX210 driveshaft is too short (it's 65, and needs to be more like 69-70mm). The first choice would be using as many existing parts as possible - especially of the machined type like driveshafts - so does anyone have suggestions for this?

It's the only conundrum to be solved to finish this prototype and I'm really eager to see this car come to life soon!