TRF201 FF, FWD Competition Buggy

[94eg!]

Wow! This is amazing! I love innovation like this. My only question is durability up front. Here in the states, we have monster jumps where it's easy to lawn dart your car into the track. With the motor up front, which makes perfect sense from a traction standpoint, how will you protect gear mesh, motor reliability, etc?

In theory you can tune areal behavior with rear wing adjustments. The major difference in the air "should" be how the chassis pitches in response to throttle input. Instead of rotating about the rear, it will rotate about the front axle/motor. This will effect how you jump. Almost like bringing the rear wheels down rather than lifting the front wheels up. Oh.....and because the wing is now so far from the center of mass, it should make the car more sensitive to wing adjustments. Notice how far forward the wing is on the other FF's relative to the rear wheels?

Thanks guys The front upper link geometry is such (currently) that the camber is pretty neutral throughout the whole travel (though the camber links are shorter than the suspension arms). With the thought in mind that the car would need to be adjusted, I made the construction such that I can put the whole plate to which the camber links mount 2mm lower. I also have spacers with which I can adjust the geometry of the upper links. If that's not enough, I can also place the plate slightly higher and opt for mounting the ball joint below the plate instead of above it. And if the plate itself needs to be changed, it's only a small plate so it won't be expensive to experiment.

That's very neat. From what I've read about FWD setups, it's all about maximizing front traction. Then from there you reduce or increase rear traction to tune the balance/handling. To me that says Camber gain will be very important up front. Should be very interesting to see how this all pans out.

I don't think it would be my choice to hang the motor right out the front - not that I'm likely to take on a project like this - but nothing says "LOOk! LOOK! I'm a FRONT WHEEL DRIVE BUGGY!" like having the motor right out the front

For FF, having all the weight in front of the axle is usually considered to aid in front wheel traction.

[Origineelreclamebord]

@Johny Retro The motor on the front is just for weight balance, If it turns out it doesn't need as much weight on the front, a mid-motor could be considered with the servo and steering on the front (for example). There are plenty ideas I have for alternatve layout and designs, but this is a good base to start with. And those characters, ah well... A final version will have that on there correctly

Anyway, I've got an update for you guys... Pictures of the finished/fully built chassis:

I also just finished the bodyshell, but I don't have pictures of that yet... I guess that will come tonight or tomorrow!

[94eg!]

Unreal man! Usually threads like this don't move along so fast. I bet your crazy excited.

[speedy_w_beans]

That's looking great! Any test runs in the street to report?

A few thoughts to maybe consider:

- Where the rear wheels attach to the suspension arms, and where the tops of the rear dampers attach to their stays, maybe add some gussets and/or X-bracing to give those features some additional lateral strength.

- Maybe use turnbuckles in place of the threaded rods for the front suspension; that way you can play with damper collar position as well as the link length and add some virtual length to your damper collar adjustment range. This is helpful with super soft and super hard springs.

- Maybe consider using longer connectors at the bottoms of the front dampers, and introduce a grid of mounting holes in the bellcrank so you can adjust the mechanical gain of the bellcrank (affecting spring rate as seen by the suspension arms) and also adjust the angular relationship between the threaded rod and damper (affecting progressiveness of the spring as seen by the suspension arms).

Again, it's looking really nice. These are just some version 1.1 thoughts to think about... Some video of this thing in action would be awesome!

-Paul

[Origineelreclamebord]

Unreal man! Usually threads like this don't move along so fast. I bet your crazy excited.

Yes I am This is a period with the quickest visible progress though: producing and first assembly of the design. Before this was a period of say 8-9 months of designing (consisting of long breaks and very short periods with loads of progress). After this will probably be a long period of testing that might not be as interesting to follow for viewers

@speedy w beans, thanks for the suggestions At a later stage turnbuckles etc will indeed be fitted. As for the rocker arms, space is tight and 1mm difference in the geometry/hole placement can already make a very noticable difference on the suspension movement. Therefor it's definetely worth looking at! As the dimensions are so close though, I think I'll opt for sets with different geometry rather than a universal set with several holes (the holes can't be placed that closely to each other).

[94eg!]

...a period of say 8-9 months of designin...

This is more of what I was expecting. Then suddenly you had a bunch of parts! lol

As for the testing progress.... All I can say is post your finding here like a diary. The development stage will be VERY interesting to me.

[Origineelreclamebord]

Time for an update. I painted the body - it's not a stunner but it works for me

It's a (very) chopped up Tamiya DB02/Leonis bodyshell for anyone that didn't notice yet!

[Grastens]

It has a good "test-car" image going, and is actually a good-looking car. Very purposeful... The front bumper is a nice touch.

[94eg!]

...The front bumper is a nice touch.

Kinda Darth Vader-ish.

[redzone]

Fully looks like a real life grasshopper! Lol

[Flerbizky]

When can we expect a video of this beauty in action?. Engineering skills = EPIC!

[Origineelreclamebord]

A video you say?

[media=]

[/media]

The parts proved too weak for jumping and eventually even this kind of driving cost me a front suspension arm (not a crash, just regular driving and a slight brush against a kerb) - the 3D printed parts are just too weak! However, I think the video tells the other side of the story: The essence of it is there! The setup was **** (It was a freaking pogo stick!) but despite that it felt quite good and the corner at the end of the straight was done flatout (not amazing with a 3100kV/12T motor but still I find it impressive for a first run and this shabby setup).

[wolfdogstinkus]

That's a shame that the printed parts broke, can you print them in a different material?, or is this just a template for injection moulded parts?

Good luck with this, really interesting design and thread.

[kontemax]

The rear end seems bouncy. Traction seems good anyway. You didn't big jumps but seems balanced.Max

A video you say?

[media=]

The parts proved too weak for jumping and eventually even this kind of driving cost me a front suspension arm (not a crash, just regular driving and a slight brush against a kerb) - the 3D printed parts are just too weak! However, I think the video tells the other side of the story: The essence of it is there! The setup was **** (It was a freaking pogo stick!) but despite that it felt quite good and the corner at the end of the straight was done flatout (not amazing with a 3100kV/12T motor but still I find it impressive for a first run and this shabby setup).

</p>

[Origineelreclamebord]

The rear end was indeed way too bouncy Kontemax. I didn't do the big jumps because I think parts would be flying off in mid-air! The material is really not up to the level even for onroad driving or driving offroad without jumping, so there I think there is no way that the material when printed with a higher fill or completely solid will be strong enough.

It's quite a big problem, but I'll have to deal with it. Injection moulding is absolutely not an option unless I'm going to make and sell say 5000+ of all parts (and then still it will be extremely expensive: More regular numbers for injection moulded pieces are between 50,000-200,000. Of course these numbers can be lower in the RC world, and the high wall thickness makes for long timecycles for each part, which contributes to their price tag).

So what's left there to do it is find a very high end 3D printing service, or machine the parts. I'll probably print a few pieces at Shapeways (the parts that are too complex to machine - and probably the nylon from their service is actually good enough for those parts), and the suspension arms and rocker arms... I guess those will have to be machined. Delrin/POM is one of the potential materials to machine it from: easy to machine with a decent tensile strength to start with

The biggest challenge will be to find a cheap spot/supplier for the machined part, and someone with experience in CAM work (I have possibly already found both, which is really nice!)

I was planning to drive the car in it's first (big) race in two weeks, but it seems that goal is out of the window... I'm going to try and make some home-made stuff (drilling and dremeling away on it to get a working set of suspension arms and perhaps rocker arms as well) and immediately make an order for the necessary 3D printed stuff.

[kontemax]

I suggest to make the rear arms with carbon fiber plates and machine only some little parts like the hub carriers, damper mounts and so on for example.

What do you think to do with the rear end set up? Softer springs? Thicker oil?

Max

[Origineelreclamebord]

It's currenty running #300 Tamiya Oil front and rear. I'm thinking 400 front, 500 rear, or 500 all around. Once I have the oil changed I'll probably also want a softer spring on the rear end/short shocks. These are the hardest AE springs available for the front end (AE Blue, 4.20 lb/in), I can probably go down to AE Silver (3.85 lb/in), and I'll also have a look at AE Green (3.50 lb/in), though I think that would be too soft. On the other hand, there's nearly no weight on it, so it might actually work!

Some drivers also told me it may need a harder spring on the long shock/front end. This means I'll have to order a pair of springs, Losi Silver and Yokomo green seem the closest match, from 2.95 lb/in (AE Red) to 3.40 lb/in... It's a big step, but there is nothing in between... If that doesn't work I'll start using front/short springs (that are available in smaller steps at this high spring rate) and use a custom spacer to make sure I can still adjust the pretenstion etc. with the adjuster ring.

I spoke about weight a bit earlier... It's an interesting thing on this car. I have measured it's weight and weight balance:

Total weight: 1470 grams (just a few grams too light for regulations - I think the sensored system, the reinforced/higher fill printed arms and sidepods will add enough weight).

Weight on front: Approx 1100 grams.

Weight on rear: Approx 370 grams.

For comparison, my TRF201 has the following weight and balance data:

Total weight: 1560 grams.

Weight on front: 530 grams.

Weight on rear: 1030 grams.

This shows I successfully managed to bring the weight balance forward on the car, and quite substantially too compared to simply reversing a TRF201. I didn't expect the FF buggy to actually be lighter than the TRF201 because of the high amount of metal hardware on the car. I think that when I would have machined arms and a race ready car though, it will weigh about the same as the TRF201.

[Origineelreclamebord]

As the first test run(s) have been made and I've worked on the car a bit I've now experienced the original design, and I've come with some updates for the car. I'll share with you the bigger changes to the car:

Most obvious probably is the holes in the suspension arms. This allows to increase the print fill without using more material: In short, the part is reinforced in the crucial areas.

The sidepods are not really as much a revision as something I couldn't model until I knew the approximate width of the body that would go on the car.

Keen eyes will also have spotted the following update:

On first glance it would affect the car in a bad way: higher CoG and weight balance further to the rear (and slightly outside). Upon the build of the V1.0 parts I came across a problem: the rear end had too much suspension movement when using the upper and lower middle holes. The only solution was to use the top hole on top and the rear of the three mounting holes on the suspension arm. I also found I needed a lot of spacing (some 5mm) to mount the damper to the rear of the three holes. The revised version solves these issues, as well as making sure the outermost settings are not used for what should become the basic setup of the car.

(The image also shows extra material around the rear axle on the rear suspension arm and the text on the side instead of the top of the arm).

Moving to the front end, I found that the outside wheel didn't seem to have enough steering compared to the inside one: the Ackermann angle was off. The image below is approximation of the old and new Ackermann geometry at approximately level suspension arms:

It's quite a difference Thanks to making the steering plate 10mm? wider (and putting the ball joints, which are the pivoting points of the steering plate, also 10mm further apart) the new geometry is reached. The inside wheel should still pull to the same angle, whilst the outside wheel on the new geometry is pushed to a bigger angle than before (some 5 degrees I think)? I think this should remove some of the understeer the car had, along with less tire wear and the ability to accelerate a little earlier out of the corners. It should also have a smaller turning radius (though I'm not sure how much use that is as long as the car can run on it's 'best' racing line).

And last but not least, I did some improvements to make maintainance easier:

The rocker arm/steering frame was difficult to remove, making the whole top chassis time consuming to remove (which in term makes it an absolute pain to replace/setup/change anything on the front lower suspension or gearbox).

Using some embossed pieces with hex shaped debosses in them, the strength of the original part is retained whilst also enabling me to undo the part just using a screwdriver. In addition to that, I decided to add more material around the rocker arm axles, as well as using large fillets to distribute stresses better.

The frame that holds the top mounts of the dampers was also rather an unpractical part. It's still not optimal (removing it from the top chassis won't go very quickly, but at least now the dampers can actually be removed from the block without taking the whole top chassis plate off (It's not visible how I solved that on this picture, I'll add it later).

That's all for now... I'm curious to see what effect the updates have to the track and trackside experience

[94eg!]

Pretty interesting. When you show the ackerman angles intersecting, it's almost crazy how much there was going on in the V1.0 (though I have no basis for comparison). Visually it looks like it's setup to make quick 180's and that's about it. I can see how this might cause some understeer. Especially at high speed (like tons of toe-out).

For the rear it seems that by moving the lower shock mounting points closer to the wheel, you'll be stiffening the rear suspension up a bit. Is this what you're going for? This will definitely reduce understeer. But from all the bouncing in the video, I can't help wonder if softening the front might be a better first step.

Great to see your making progress and revisions. This is very interesting stuff.

[Origineelreclamebord]

Yeah I know, the ackermann angle on the old one is pretty horrid! I think it will help to make the car understeer less, not that I think it was that bad at 3000kV, but at 5200kV those front wheels better work together like clockwork! This should also help it to carve tighter lines - very handy for overtaking manoeuvres, evasive actions etc - and that can make or break your finals in the opening lap(s)!

The rear suspension on the same setup will indeed become stiffer, but as the whole damping/spring setup needs an overhaul it's not that big a deal. The main point was to reduce the amount of travel the rear suspension arms had, and in particular the amount of droop needed to get a 'regular' ground clearance:

I think this image shows pretty well what the difference to the suspension travel is? The ground clearance (at 0mm droop/no load on the suspension arms) is now roughly the same between front and rear. The uptravel looks like it's bigger than it has to be, and perhaps it is. I designed the uptravel so each end of the car can hit the ground when both ends are compressed towards the ground, but also when only one side is - so in case of the rear end, it can bottom out if only the rear end is compressed. If it's the right way to approach the travel of the rear suspension, I don't know. I guess I'll find out (I think it could prevent breakage or other damage to the rear arms on hard landings).

[94eg!]

That's a sound theory to me. You definitely don't want the rear suspension binding up before the chassis hits the ground. Otherwise your looking at unnecessary suspension stress and breakage. I imagine any excessive compression stroke will simply go unused. It will also be interesting to see how the dampers react to this. I think typical off-road setup uses a "pack" to setup the cushion of landings (adjusted amount of air inside the damper). If you have too much unused compression stroke, you may have to really fiddle around with the shock bleed screws to get it just right (less air I imagine).

[Origineelreclamebord]

It's time for an update! For those of you who didn't see it yet on oOple, here it goes:

I drove the car on saturday... I really like it! Better damping/spring setup, quicker with the more powerful motor - eventually anyway The car had a lot of wheelspin. Also, it seemed to understeer the same or more as the first test - that could be anything from setup changes, different ground/terrain, the motor, even the amount of profile on the rear tires!

After the first run I got a set of 4WD front Proline Caliber tires - with a cut profile for more forward grip - mounted on rear wheels. I put this on the front end. The understeer was reduced quite a bit! It could be down to the width, the cut profile, or even that the inside wheel balloons less through corners.

Perhaps the most important thing I found out in the test runs: It's durable enough to jump now, and it's not a handful to jump either! In fact, I think this car flew easier and was easier to adjust in the air than my TRF201 was with that motor fitted! The only thing it couldn't do was clear the jumps with a short approach - the doubles on the track. That's down to it's ability to accelerate hard though (or the lack of it), not it's ability to jump.

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 front 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:

There we go! Also, There are two videos of the car:

[media=]

So eh... Enjoy (I hope)!

[Gruntfuggly]

Great work - really enjoying this thread.

It is ugly though - but in an endearing way.

[Grastens]

Function over form, but what function! I was very impressed by the videos, and continue to marvel at all the work you put into making a custom FF buggy work like this!

I admit I am still a bit confused about the explanation of the change in uptravel in post # 45, though... Is it for consistency on landings if the chassis bottoms out?

[PaPeRo]

Wow very cool project. Did you consider machining the arms out of delrin?