FWD/FF Buggy

[Origineelreclamebord]

Thanks guys! The car felt great, and it's really rewarding to see the performance of the car improve so much since the first run with it some three months ago

@skyaflake: I'm studying Industrial Product Design - and imo, one of the biggest (and most rewarding challenges) is realizing the product ideas (CAD Modelling, Working with the balance of strengths/limitations of different production methods and materials, using 3D printing/rapid prototyping). After all an idea for a product is still just an idea, but the actual product than results from it can be experienced by anyone - and depending on what you make - virtually everyone!

...So this project is where those interests and my hobby kind of meet together

[Origineelreclamebord]

Elvo has made another video of the car in action, this time on a dirt/clay track (LINK)

The track is quite challenging for the FF because of the short run ups to the jumps (in combination with the bumpy surface) - there were plenty of RWD drivers also struggling to find a setup and driving style where they could consistently and comfortably clear the jumps.

Some people might also remember the track from these videos (LINK 1 - LINK 2), which is last year's test of my first prototype on the same track - with tiny layout differences: This year's track has more challenging jumps overall (doubles instead of tables or a single large jump).

In the (new) video, you can see me driving the car (0:00-2:32), and two other drivers (2:33-3:15 and 3:16-3:35).

It should take no expert to see that setup-wise it's not there yet for clay. I removed all of the rear weight and added stuff in front of the LiPo to make sure it'd clear the jumps without driving extremely wide lines, but it makes the car very unsettled over bumps (even more so as I've softened the front but didn't have time to do the rear as well). I struggled with it, and I think so did the other drivers (who are both better/faster drivers with their RWDs than I am).

That's a big difference though: last year's prototype could clear none of the doubles with a short run-up, no matter how wide a line I took. This car's acceleration is far superior, which results in a car that can clear the jumps. It takes some practice, but eventually I could do it without taking much wider lines than usual, and track conditions were pretty much the same to last year (slightly damp from rain the evening before).

Also, this car manages tighter corners than the old car, with a lot less understeer, and does so at higher speed... If you drive properly and don't slam it into the wall at the end of the straight that is! I'm still wondering how I managed that, but the good news is that the car came out unscathed!

I also have video footage myself with the try-outs of a wider front end on the car - I will upload it soon. In the meantime I'll also think of what things could make the car more balanced and stable, and if possible without sacrificing forward thrust (= no added weight on the rear)

EDIT:
Here is my video (LINK). I added some info on who the other drivers are. It makes it clearly visible that the pace is not 100% there on clay yet. However, pace is still promising, and I think if I'd give the driver a few packs to train with this car (instead of just handing it to him) and improve the setup, pace will be very close to the A-finalists that passed him in the video. I'll list what's wrong with the setup in the video:

1. Old/Worn front tires (cut with a Chevron profile to try and gain a bit more traction from them).
2. Too low ground clearance on the front end (I couldn't increase the pretension with the adjuster ring and didn't have a spacer at that moment to correct it with - so it was 2-3mm too low).
3. Too stiff damping+spring on the rear end (front end was corrected to gain grip, but I didn't have time to adjust the rear for the video because there was bad weather coming).

In the video Elvo made, the car does have the right ride height, and newer tires... but the rear end is still too stiff on that video as well - even more so because I removed 30g from the rear to try and gain more traction (not a smart move for stability). The stability is something I'll adress on the next clay test.

[Origineelreclamebord]

Time for an update I wanted to put on the car for a long time. It's been in the making for quite a while, and it's finally done!













So, first thing that you may notice: Most parts are black now, and the remaining parts will be painted soon. I liked the white plastics, it's more contrasting, but it was more brown/beige lately, so this makes the car look neat again.

That's not really what the post is about though, that is the revised front suspension! So what has changed?

Well, first of all, the car now uses long (DEX210 rear) shocks on the front end. This increases upward travel and increases droop. It also utilizes the DEX210's original shock tower/shock tower geometry. So the car no longer needs an extra set of front shocks, no custom front shock tower and no more requirement for two sets of front springs for full setup adjustability. Though it's still a goal and not a certainty, that does help to make the idea of a conversion more realistic (it reduces the costs of a converted car by up to 55GBP).

Anyway, to make this system work, the car did need new suspension arms - with a gullwing shape. This gave the opportunity to update some more things, too!

For one, the arm only has two damper mounting holes anymore - the inside mounting hole is now at the point where the outside hole was before, and the other one is further to the outside. The hole to the stabilizer is slightly further inside to prevent rubbing between shock and stabilizer. Also, the suspension arms are 0.75mm longer, so the car is slightly wider now. Lastly, The arms have a 1mm shim at the inner hinge pin, and another one at the outside hinge pin. This allows the front hubs to be moved forward to test if this could make the car handle more neutral particularly in high traction conditions, where the forward traction is of less priority than minimizing the overhang of the motor.

The system feels quite smooth on the table (I'd say better than the previous front end) - so that's a promising start! If all goes well, the system is due to be tested Sunday in a club meet on clay

[Losi_110]

Hi looking good hope the testing goes well with the new bits. You know looking at the pic straight on from the front of the car is quite a strange view as it really looks like it should be the back and gave me the thought of I wonder what it would be like running the other way as a car with rear motor but rear steer if you turned the epa down I'm guessing probably horrible but we used to have a laugh trying to race old mardave minis with rear steer lol.

[Origineelreclamebord]

Originally Posted by Losi_110

Hi looking good hope the testing goes well with the new bits. You know looking at the pic straight on from the front of the car is quite a strange view as it really looks like it should be the back and gave me the thought of I wonder what it would be like running the other way as a car with rear motor but rear steer if you turned the epa down I'm guessing probably horrible but we used to have a laugh trying to race old mardave minis with rear steer lol.

Haha, I haven't tried it but it would drive really awkward - Wheelying almost all the time and cornering like a forklift

Unfortunately, the rain changed my plans and I didn't go racing. The weather did clear a few hours back though and the local parking lot was dry enough to do a test drive. Of course it's not a proper test being that I took it onto the tarmac with any setup changes (even with some old clay tires that balloon to twice their diameter), but it was fun nonetheless!

[fastfilli]

Hi Origineelreclamebord

I have been watching this thread with interest for some time to see if there is any potential for a FWD car.

I race in the UK on super hi grip Astroturf and the current craze is to take the front drive shafts out of a 4WD car and run it as a 2WD car. This seems to work great as the weight of the car is more forward and stops wheeling under hard acceleration.

Last week a Schumacher K1 driver snapped the rear belt on his car, so to get him buy for the night he put his car into front wheel drive.

Shock horror he set the fastest time of the day and pole position in the A main.

There were some top UK drivers at this meeting so the competition was hi and this guy was 0.6 faster per lap.

In the final he overheated the slipper as the car had so much drive :-/

One comment that stuck with me was he found no benefit from running wider front tyres? Settling for mid width front tyres!

Another guy tried the same with his Durango but it did not work at all. The shaft drive car did not produce any front drive ?

Hope this may be of some use to you. Best of luck with your car ;-)

John

[Origineelreclamebord]

Really cool story John, thanks for sharing! The wider tires are a necessity due to 2WD regulations unfortunately, I recall both the EFRA and BRCA state that a 2WD car should use wide tires on it's driven wheels. However, for the FF it may indeed be beneficial to stick with 4WD front tires for various reasons.

First of all because of the whole front suspension, because I can then important a 4WD front suspension onto the car. This makes it cheaper, easier to develop (as there are more driveshaft and front hub alternatives out there). The car would have a smaller scrub radius too (distance between tire contact patch and steering pivot of the front wheels), and the dampers could be placed further to the outside on the suspension arm. And when you look at the tires themselves, narrower tires can't balloon as much as wide ones - especially of soft/clay tires - which means the actual contact patch under hard throttle doesn't actually differ much from wide tires and is more consistent than wide tires. For high bite tracks a narrower tire may also work because it corners easier - after all your diff helps to turn your car more easily, but that only evens out the necessary difference in rotation speed of the left and right wheel, it does not correct for the different rotation speeds that would be ideal throughout the width of each individual tire.

This combination of lack of ballooning and narrower contact patch is what helped the first prototype's pace a lot on clay during the test in Bergschenhoek last year. Note the pictures in this video, the front boots are 4WD front tires stretched on 35mm wheels (so slightly wider than 4WD front wheels, but narrower than modern rear wheels).

As for the K1's better performance over an FWD Durango, I think it's down to a set of factors. For one, the belt drive should help to 'give' a little, acting as a damping feature in the drive without slipping (thus helping the smoothness of the drive and adding grip over the direct drive of a metal drivetrain). Also, the K1 may have been running ball diffs, not gear diffs (I found a gear diff only worked on my FF if there was tons of grip - so for a 4WD even in high grip conditions the ball diff's smoother way of providing drive may have helped here).

Then there is the motor rotation direction that may also play a role: Whereas the K1's motor can pushes the front of the chassis onto the ground on throttle, the Durango moves it from side to side. So the K1 is counteracting the weight shift of the acceleration, the Durango is not and is actually making uneven wheel loads, possibly causing the diff to activate on acceleration alone.

Despite all that, I'm surprised and happy to hear the FWD K1 did that well! The weight balance of the K1 you'd say is far from ideal for a FWD car. Could you tell me more about the track and conditions? Did it happen to be quite open and flowing or is the astroturf really that different in the UK? (I can't imagine FWD 4WDs having enough grip to work their way to the top of the 2WD rankings on astroturf tracks I've driven on in Belgium).

[Mike2222]

I am also running a K1 in front wheel drive mode. THe only changes I have made are to relocate the esc to the top deck, which means I can use a shorty lipo up front ( it sticks out beyond the chassis but is covered by the shell). I can also use saddles inline on the RHS, or across the rear when I use it as 4wd. The front wheels are 4wd fronts to keep within the allowed width limits. The BRCA rules specify a control tyre in some competitions, but they only quote brand type eg Schumacher mini-spikes. No mention is made of tyre width so 4wd fronts are legal. There are some inconsistancies though, as the 2013 National entry form quoted a control tyre for the rear wheels only, the front tyre choice was free!
I find it easier to drive than rwd, so I shall continue to use it as fwd.

[Origineelreclamebord]

Sounds like a nice layout - could you make some pictures of it?

As for being allowed to run front tires, that's an interesting one. The following rule applies here:

Originally Posted by BRCA 2013 1/10 Electric Off-Road Regulations

23.11
At Sanctioned events two types of control tyre will be adopted for the driven axle on 2WD cars and the rear axle of 4WD cars. The choice of tyres for the non-driven axle on 2WD cars and the front axle on 4WD cars will be free, subject to conforming to rule 23.7. The Section committee will approve the choice of control tyres. The make and type of the control tyre s to be used at National events will be specified on the National Championship entry form and also in the confirmation document. There will be no restriction on the number or compound of tyres used.

This rule was changed November last year from 'control tyre on rear axles' to 'control tyre on driven axles' - probably to make sure a FWD buggy wouldn't have an unfair advantage of free tire choice on the driven wheels.

The fact that they don't consistently state whether it's all tyres of a certain type or only the 'rear' ones is a window of opportunity... not just for FWDs by the way, RWDs and 4WDs may also benefit from narrower tyres on the rear if the grip is there for the same reasons of reduced ballooning and less rotational friction of the tyre through corners

It could be really interesting to look into, but I'm afraid the mass use of narrower driven tyres will result in a ban - let's hope not though, being able to choose for narrower tyres is a great way to play with a car's handling, and in the end is probably still a trade-off between different handling traits (I can't imagine narrow tyres work everywhere). And in the current situation, the FWD would need two front suspension systems to really make the best of narrower tyres - of course you could also use two different wheel/tyre combos, but then you still have some things like scrub radius tat could be optimized on the front end when using 4WD front tyres.

[Northy]

Now the interesting thing is that it was Mike2222 who proposed the rule change

G

[fastfilli]

Hello again Origineelreclamebord

The track I race on is very fast and very high grip. It is usual to use a 6.5 motor or a 7.5 with lots of timing.

On this weekend Silverstone Buggy Club laid out some slippery surfaces which I personally believe was an advantage for the Front Wheel Drive car. If I pushed too much on these slippery parts of the track my car would spin out and end up facing the wrong direction

The driver of the front wheel drive car reported back he had chronic under steer on these sections but not possible to spin out

There was large double jumps on the track which was no issue to the front drive car.

From what i gather the front drive car was super easy to drive fast consistently because it was so easy to drive e.g. NO wheelying, No under steer coming on to the strait and No spinning out.

Throttle control less important???

[Origineelreclamebord]

Thanks for sharing, that sounds really good!

They are indeed very easy to drive. Throttle control is of importance for two factors:
1. Maximum acceleration on most surfaces will be reached with minimum wheelspin (just like ABS helps to stop a car quicker than sliding/slipping tires).
2. Tire life (I found) to be greatly affected by the amount of wheelspin. On dry astroturf some agressive 2WD drivers managed to wear down tires as much in 2 minutes as I did in 3 entire heats

That said, the consequences of using too much throttle on an FF don't have a big impact on lap times simply because the car misses a bit of pace through/out of corners, not ALL pace like a RWD does when it spins out Through corners, too much throttle is easily noticable by the car taking too wide a line and some understeer - it's easy to correct. Out of corners it's harder to spot the lack of acceleration, so it's harder to correct too, but still easier than learning to drive an RWD quickly.

The understeer the driver has got on his FWD Buggy probably is down to the front stabilizer setting and/or having too much rear bite. I drive my FF with a stabilizer on dry astroturf and grass, and without one in the wet. Also, if the car is using a gear diff, switching to a ball diff may help in this situation too.

[mro_racing aka Doorbell]

Who did the new 3d printed wishbones?
the quality is very good

[Origineelreclamebord]

All 3D printed parts on the second prototype come from www.shapeways.com - It is nylon (called 'white, strong and flexible' on their website) and is more costly than the parts on the last car, but these have a better surface finish and are stronger than when printed with a (DIY/Consumer FDM) 3D Printer.

Admittedly, some parts on the car would still do fine made from the old material (only the suspension arms didn't hold), but yeah well... if it doesn't break anyway, you're only spending the money of the more expensive material once

[Origineelreclamebord]

Small update: I was contacted by Noel from Cream RC, and he offered me a Cream Carbon DEX210 Rear Tower - it looks awesome, it really compliments the car - and I'm sure it will really help the car's durability, too! Thanks Noel! This is what it looks like:






The pictures are from a small tarmac test with the car - it was hard getting anything decent on the pictures with the speeds the car had, so these are some pictures at moderate speed. The car went quite well on tarmac with just a stabilizer added and droop reduced a bit. It still grip rolls quite easily, but that's because the tires/inside tire balloons a lot under acceleration: no stabilizer can help against that So I'll try that soon, too.

[Origineelreclamebord]

Another update. I now painted some more stuff, and I dubbed my car 'The (not yet) Legendary Black Beast of Aaaaarrrrrrggghhh!'













It's quite black alright! I prepared the car to look neat(ish) for tomorrow: There is a 3D-Printing fair in town, and I've been invited to come over and show off the car It should make a fun day, and it's a great opportunity to find a sponsor/partner on the 3D printing part of this project too!

I also tested the car (again) on tarmac to test some different tires. These dBoots don't balloon as much. so it almost looks as if the suspension is finally doing the work instead of the tires. I finally felt confident in throwing the car through corners - I even increased the droop on the front again to take the understeer out. The move to the dBoots staggered ribs on the back really works, too: It has exactly the minimum amount of grip needed to stick to the road under my usual driving style! I'm ready for tomorrow!

[Origineelreclamebord]

The car has been tested on clay on September 21st. The overall feel of the car was similar and the points of improvement were still the same: More weight on the rear, try the car with tires that weren't worn and disconnect the stabilizer (as it was clay after all). However, before I could do any of that (apart from disconnecting the stabilizer), the car broke down.

Upon inspection it became clear there is a durability issue with the new suspension arms. A wrong knock during some cartwheeling action broke the arm behind the caster block. Since the new front end was the center piece of the test, I retired the car for the weekend.

Despite the mere 3-4 minutes of track time I did get a good impression of the difference the long shocks make on the car. Like I stated earlier, the overall feel is not very different. However, there is a distinct difference: It seems the car is less bouncy on the front end and more in contact with the surface thanks to the increased droop levels. I think the rear end needs some tweaks (like extra droop and more weight on the rear) to get it properly stable, but it felt pretty good.

To solve the durability issues, I've gone back from the gullwing design to a straight arm. The 3D model was causing problems with every small edit I was making (I won't get into detail on that), and because this requires only one front arm in the spares box once the new front end is approved to stay. It's been ordered, so I should have the car up and running again in two weeks time.

So here it is:


The new arm has inherited the open structure near the outdrives from the gullwing arm, but the area around the caster block is a lot like the first set of arms I had on the car. In fact, the current arms are the most beefed up of all three arms, so durability concerns should be out of the window (again)

The new arms will be able to use the DEX210's shock tower geometry. It will not have as much uptravel as with the gullwing arms, but still enough to bottom out. The droop levels will be the same, being that the suspension arm (thus also the shock) are limited in angle by the chassis plate.

[GrahamH7060]

I must admit I really enjoy following your thread , your attention to detail is second to none !!

Good luck at the show I'm sure you'll have no problem gaining interest from any of the 3D printers !!

The beefed up wishbones do look good , I'm sure they'll take any abuse thrown at them , although the gull wings looked super cool , I guess sometimes function overules design !!

Did you have any further joy with the wing mount option ?

Keep up the great work

Graham

[Origineelreclamebord]

Thanks

The 3D printing fair was nice. It turned out there was someone else with an RC car too. He made as many things as possible 3D printed using an affordable consumer printer - even the transmission was 3D printed!

There was lots of interest for both our work - in the end I didn't find a sponsor, but I think I have shown the potential of 3D printing under high stress applications. Also I've handed out and received some business cards, who knows what happens with that in the future

The gullwing wishbones is something I had to get used to, and now I start to like them they need to go Ah well. On a car with pricy spares, symmetrical stuff is better in the end.

As for the wing mount, I take it you mean the DEX210 wing mount? It's a bit off-topic, but here's the story: I've had it printed, but one measurement I made (that of the lower mounting holes on the gear casing) was 0.5-0.75mm off as it turned out, due to which it didn't fit at all! I've tweaked the model and it's being printed again, together with the suspension arms.

It's just a matter of fitting it now - once it fits I'm completely comfortable saying it's strong enough: It has more material around the screws than the regular 210 mount (the same amount in the framework itself), and knowing it's strong enough for even suspension arms, it's certainly strong enough for wing mounts

[skyaflake]

Still a great progress. I enjoy reading all your stories and optimizations. Keep it going!