54 replies to this topic

[Origineelreclamebord]

For some of you this sight might be familiar already from oOple, but being a Tamiya based project, I really yhink I should post this here as well I present to you, the TRF201 FF:








oOple Development/Build Thread

Specs/Features List:
- TRF201 Gearbox (with Ball Differential and Slipper Clutch).
- DB01 Front Uprights+Caster Blocks.
- TRF HL Aeration Dampers.
- Double Wishbone Front Suspension with Inboard Dampers.
- Trailing Arm Rear Suspension (2 Degrees Toe-In, -2 Degrees Camber each side).
- Developed for use with a Low Profile Steering Servo and 'Shorty' (=95mm long) LiPo Stick Pack.
- Compatible with modern Pin-Type Rear Wheels on the whole car.
- BRCA, EFRA and BNK Legal to run in 2WD Dlass.
- Approx. 284mm Wheelbase, 250mm Width.

Existing/Production parts in the design:
- TRF201 Gearbox.
- TRF HL (TRF201) Aeration Dampers.
- TRF201 Steering Arms+Servo Saver.
- DB01+TRF201 Suspension Blocks on the front suspension.
- DB01/DF03 Hybrid Universal Shafts (DF03 70mm dogbone, DB01 rear axle).
- TRF201 45mm Titanium Turnbuckles (for camber links).
- TRF Adjusters on the whole car.
- DB01/TRF Rear Wheel Axles (for the rear wheels).
- 4x Pin-Type Rear Wheels.

[94eg!]

Reverse rotation motor???

Why not use FF03 gearbox? Internal ratio & slipper I'm guessing.

Pretty darn cool. Leonis body looks way better on your concept vs the DB02.

I see positive camber in droop at the front. Interesting. Any particular reason for this?

Any particular reason you've got the front pushrod suspension mounted to such a high tower? Space perhaps?

Needs a front bumper for motor protection.

[Origineelreclamebord]

Thanks for the comments and questions! I have a TRF201 as a racer, so it makes sense to use one spares pile for two cars. At least, that's why I initially chose for a TRF201 as a donor car (at the end of the project there weren't many TRF201 parts left on the car though). If I'd have to choose now it would be the Durango DEX210's gearbox, for it's nice slipper clutch (adjustable without taking a cover off), and for the fact you can construct it any way you'd like (3-gear, 4-gear, motor plate on either side from what I recall too).

The FF03 gearbox is not really an option as it doesn't have a slipper. The slipper may prove to be an essential feature to aid forward traction on the car (making power delivery more fluent, even if a slipping motion isn't a very fluent one by nature, it's more fluent than no slipping feature on the car).

The reason for the high rocker arms is to clear the tie rods when the suspension is pushed completely up. It was extremely difficult making the whole front geometry work. If the spur gear/slipper clutch assembly wouldn't be in the way, the rocker arms could be mounted way further to the front and they could be placed probably some 10-15mm lower (making the shocks sit approximately horizontally).

As for the positive camber, what you're seeing is actually toe-out (though that's hard to tell on that picture). The camber would become slightly more positive, but by less than half a degree. Playing with spacers and the alternative mounting holes for the inside mount of the camber links could help determine the best geometry in a later stage of the project

The front bumper... You're right about that! For the first runs I may be forced to use the TRF201's stock bumper, but I'm looking at making a bendy, soft bumper on the front in the same shape as the 201's, but with more room to flex towards the motor and motor mount (without hitting it). Something like a bent 1.5-2mm polycarbonate plate could work very well for this.

As for the rotation direction of the motor, I heard motors (at least brushed ones) are often more efficient in one direction than the other. Is this true, and/or is this the reason why you're asking it? Because everything I've done so far with brushless motors seems to go well, and I've not taken the rotation direction into account at all!

[speedy_w_beans]

Please don't take this as a negative comment. I'm just trying to imagine how it will really perform.

I think this is an interesting design, but I'm wondering how effective it will be. Like a front wheel drive car, when the front wheels start spinning forwards the equal and opposite reaction is for the chassis to want to rotate backwards, transferring weight off the driven wheels. Also like a nose heavy front wheel drive car, slow steering response and understeer will likely be the dominant traits unless you put a beefy anti roll bar in the back. The large rear suspension arms go against the usual goal in suspension design, which is to minimize unsprung weight. As the suspension arms become larger and heavier, your ability to dial in the springs and dampers for the rear will be hampered.

For a quick test without a lot of effort, just try driving a TRF201 in reverse on dirt with low steering EPAs and see how the acceleration compares to driving it forwards -- the tires probably slip a lot when going in reverse. What you're showing in these diagrams is a buggy driving backwards with a bulkier trailing arm suspension geometry.

-Paul

[Origineelreclamebord]

Hehe, I don't take it as a negative comment, I understand your concerns. For me, this project was purely because I'm interested in these cars, and I was impressed with the handling of my FF01/DF01 FWD Buggy, it was different, challenging and fun!

But through the process of the project I have become more ambitious. I'd like this car to keep up with the RWDs (in the right circumstances of course). If you look at performance, this type of design has proven to be successful in the late 80s/early 90s (This link shows some old images and a similar FF project a few years back). Supposedly they were successful because they were more stable than RWDs, but in the hands of a pro this doesn't matter much if you ask me... So I think there's more going on.

The following lines are based on what a contact of mine about the physics of the FWD car(s). He said: 'Look at full scale (touring) cars. The RWDs might be quicker off the line, but FWDs carry more speed through and out of corners because they go on the throttle earlier. It also shows that once the car has some momentum the wheelspin is not a (big) problem anymore. So, key is to make sure you keep your momentum. As the FWDs carry more corner speed it makes even more sense to keep the momentum. This may well apply to the RC cars as well.'

I know on low grip surfaces (clay for example) the wheelspin might also occur at higher speeds, and here is where it gets interesting: How does it affect the car? Does the higher cornering speed weigh up to the wheelspin? And how about higher bite surfaces, such as astroturf? I haven't found any source of information of these cars being tested on astroturf, and it should be very interesting to see how it performs on that

Take a look at this video. It shows the FF buggy (the Fluor Yellow car) from the link earlier in this reply/post (the FF buggy from BloodClod) in action. If you look well you'll see that the back breaks out every now and then, only to be corrected...By applying throttle. It is a nice giveaway that shows how early these cars go on the throttle, and it's not hard to spot that the car seems to carry more speed through the tight bends.

So if it goes well... I think it will. If it goes well enough to keep up with other 2WDs... I hope so, but I am not putting my expectations that high! If it does, then it's a dream come true, if it doesn't but performs well on it's own (balanced, fun, and if it leaves no big gaps in the potential of an FWD buggy) then I'm very happy nonetheless!

PS: As for your concerns of unsprung weight... The arms seem big, and they are, but they are 3D printed with a percentage of filling. That means they are actually partially hollow inside (and pretty light for that matter). Also, the best performing FWD buggies had these long arms on them. So as we need a car to recover data from, instead of looking at pictures of vintage FWD racers and speculating about what would/could/might work, I think it's ok to start with I agree with you though, it's worth looking at if such long arms are really the way to go, and/or how they can be made lighter (sure 2WD rear wheels and tires would help, perhaps I can convince the BRCA to change the regulations for FWD cars specifically to allow 2WD wheels on the rear).

[94eg!]

Man that is so cool. I wish you luck. You should hire a pro-driver to help you experiment & tune it.

Yes brushed motors are setup to run one direction. You can always re-clock the timing though to run backwards. Not a big deal. I forget brushless doesn't have this limitation. I've only dabbled in brushless setups a little bit.

BTW: How did you pick the instant center for pro/anti-squat in the rear suspension (trailing arm pivot point)? DId you follow a previous design? I've been learning a lot about suspension tuning, but can't seem to find anything to help understand how anti/pro-squat geometry effects FWD.

I ask because I'm into Honda suspension tuning. My civic features a complicated trailing arm / multi-link configuration. One company makes offset trailing arm spherical bearings to help correct the bump-steer curve on lowered cars. My concern is that this offset also slightly raises the rear anti-squat geometry, and I would like to fully understand how this effects behavior of a FWD.

The rear upper & lower arm control camber. The small forward arm controls toe. The entire trailing arm rotates around the large central bushing:

[speedy_w_beans]

Thanks for the link and video. BloodClod's FF buggy looks pretty good. I wonder what motor he used - stock, super stock, etc. you mention that carrying momentum is key; that seems to imply sweeping consistent turns because the momentum that can be carried is a function of speed, turning radius and tire grip. Decreasing radius turns and point/shoot driving style might not hold up...

Regardless, it looks like a fun project and it will be interesting to see the results. Are you going to test with something hotter than a stock motor? A decent modified motor might reveal the capabilities and limitations of the chassis more... It'll probably force a driving style different from a regular TRF201.

-Paul

[Tamiya1/10]

The plan view looks "interesting", do you see what I see?

I gather the battery will be located at the center of the chassis and the receiver on the other side opposite to the servo?

Always like 3D dwg.

[kontemax]

This is beautifull:

https://www.google.i...iw=1280&bih=871

The first FWD buggy I suppose.

Max

[Origineelreclamebord]

Wow, what a response I have a race today, so I haven't got much time currently. I'll reply tonight. First I need to glue some new wheels and tires (kind of my breakfast, too )

[Origineelreclamebord]

@94eg!: Thanks I got my parts produced by Atomic Carbon - the guy I'm in contact with there has some interesting contacts with British Pro drivers who might be able to test it for me. Also, I have some very talented drivers at my club (and a few very experienced ones when it comes to setups and vehicle dynamics), so I'm sure I can get the car thoroughly tested.

I wish I could be of help with the trailing arm geometry, but my understanding of suspension geometry is still pretty basic (imo). I decided for this geometry as the rear end seems to be of way less importance on these FWDs, it's only to keep the car stable. Also, the geometry is approximately the same as on successful FWD buggies from the past.

@speedy_w_beans: Yup, I'm also curious about that. I'll be running a 5200kV/6.5T motor in it (I ordered it yesterday night). I drive 4600kV in my TRF201 but that seems a tad light on the bigger tracks, so even though an FWD shouldn't have a mad motor, I think it's only reasonable that my FWD needs to handle such a motor. The driving style will be very interesting indeed, I expect to drive lines that on first sight look like someone's missing the apex, driving as wide as possible without hitting the dusty part of the track (as the dust may prove worse for the wheelspin/forward grip than driving a tight line).

@Tamiya 1/10: Receiver will be an interesting one: ESC will be on the left, Servo (low profile) on the right, 'Shorty' LiPo pack in the middle… But the ESC I ordered is quite large, so I guess it'll sit somewhere on a rear suspension block, wing mount or an edge of the top plate

@Kontemax: I restored one of those. Nice cars, a little short on wheelbase and weight on the front if I look at the chassis – but I never found that out in practice, I was too afraid to damage the freshly restored car… A shame I didn't try it! It's one of the only production FF buggies I think… You had this, the Nichimo (Spirit) FF and the MRC Sand Master… Perhaps others, but I don't remember them now or don't know them ;-)

[kontemax]

Actually this is the most interesting tread in this section.


Max

[kontemax]

Don't forget this great masterpiece from the japaneese member Grahoo:

http://www.tamiyaclu...d=21774&sid=418



Max

[speedy_w_beans]

Very nice photo show of that FF chassis. There's quite a bit of work and craftsmanship. Did he ever write about how it performed? For that matter, has anyone ever written about how FF chassis perform compared to mid-motor and rear-motor chassis?

-Paul

[Origineelreclamebord]

Very nice photo show of that FF chassis. There's quite a bit of work and craftsmanship. Did he ever write about how it performed? For that matter, has anyone ever written about how FF chassis perform compared to mid-motor and rear-motor chassis?

-Paul

I'm not sure... If it has been done, I didn't find it. It either was left on paper (as the majority of the FF protos were built in the pre-internet age of course), it's not out there in English... Or I should look up the statistics about Google... I've heard rumours it only finds about 1% of all the websites out there... I'd be interested to see if that's true!

Anyway, all the footage, info etc. I've found are about 3-4 FF buggy protos done after 2000 (and hence are reasonably well documented on the internet), some stuff from old RC magazines, a review of the MRC SandMaster (I NEVER hear people about this car, so I found it pretty special to find a review about it. It's also in French, I recall there was good interest for FFs in France back in the day) and most of that could be as much as loose scraps of paper as my French is kind of artistic and creative shall we say (I'd make a very funny Interpreter ), and my Japanese is literally second to none Anyway, I still uploaded in anyway, it's in this album (link). Some examples pasted in the topic:

The 'Ryuz FF,' probably the best documented FF proto of it's age.




It's the basic layout the best documented protos from back then looked like, as you can see the layout on my car is very similar so I can extract information how this layout (which is supposedly the best) actually performs.

Home-brewn conversions (and the MRC Sandmaster, bottom picture in 'first' page) in a French magazine:





I've tried to contact BloodClod, but not with much success. I also contacted Grahoo, and got some great old school footage of his first version FF proto:


I think ANY vintage enthusiast will generally love this though, it's footage of a 'Tamiya RC Grand Prix,' showing an Avante ad, what Tamiya GPs looked like back in the day (1988)... and some footage of the FF buggy! (1:08-1:26 and, a short pass at 3:05 and from 3:25 onward he's some time in the lead until he makes a mistake).

This video shows the same old footage cut down to the scenes in which his car is visible, plus footage of his Mk.2 Poprod (pictures and after one minute also video footage):



The relatively ill documentation is part of why I want to be so open about this project... I had great difficulty finding anything at all, so if I develop this car and then go through a process of making improvements (if the basic performance is there), why should I not share these efforts and save other people a lot of time trying to find out stuff that is looked at as being so simple and logical afterwards?

[speedy_w_beans]

That's some great reference information you've dug up! I'll follow your thread as development on your buggy continues!

-Paul

[94eg!]

Yes, very extensive. Again thanks for treading new & old ground and sharing it all with us.

I hope to see the feedback & setup information from some of the more experienced drivers (yourself included). It's amazing how much RC information transfers over to 1:1 scale. Have you done any studying on modern on-road FF setup information? With the popularity of the FF03, I wonder how much has been documented on setup. There has to be a large thread going over on RCTech.net.

[speedy_w_beans]

This is a nice series of articles on setup for 1:1 cars; it correlates well with the available information on RC car setup:

http://www.modified...._1/viewall.html

The key concept that made the greatest impact on my tuning is how tire loading affects slip angle. Once that concept is understood, then the effect of each suspension adjustment becomes clearer.

-Paul

[94eg!]

I'm talking about FF specific tuning for fine suspension adjustments like droop, anti-dive/squat, roll center, etc...

General setup charts Hudy are all over the place. But being FF can change things significantly (like shock setup for drag racing is completely backwards).

[Origineelreclamebord]

I haven't really looked at FF onroad cars or 1:1 cars yet, but it would be a good source for setup and suspension geometry info. Thanks for the heads up on that!

Anyway, I think it's time to share some nice updates.... I collected the parts from the post office this morning... I've currently got an assembled car in front of me with working suspension! I'll take some good pictures tomorrow when it's light again, for now I'll share some pictures from the build:


The Printed parts and the carbon goodies. Note: On the right are some printed plate parts. Once the first one or two test drives have been done I can get these made from carbon (hence, if any adjustments are needed, they can be done now without wasting money on another new carbon part and throwing the old one away).






Notice the right driveshaft isn't in it's outdrive? The diff nut and spring are slightly in the way, despite all the CAD work! I can only hope the guy who I bought this 201 from has built the diff wrong (which I have to admit is quite easy, the manual isn't clear about it that you need to flip the diff around at some stage in the diff build).







There are a dozen revisions I made on the parts, from small dremeling to potential geometry changes, but overall it looks pretty good: I even have more clearance between all the different links on the front than I expected!

[speedy_w_beans]

Very cool.

-Paul

[94eg!]

Man that's great! Must be so fun to design & test your own chassis. Hope it goes smooth.

Just from a few seconds of viewing, I do have one comment. The front suspension looks kinda odd. Kinda like parallel arms of equal length. Typically the upper arm is shorter for camber gain, and at an inclined angle relative to the lower arm to bring up the roll center. Of course all these setting would need to be tweaked with extensive track testing, and I have no clue about the process of race-chassis development.

[RichieRich]

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?

[Origineelreclamebord]

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.

As for protecting the motor, for the first one or two test runs I can't go to a track (too far away), so I'll just do some easy testing on it and mount the standard bumper. In the meantime I'll work on making a big, flexible flap (I have a lot of spare 2mm lexan, so chances are I'll use that) at the front. This should help bring the car to a less sudden stop and should prevent me from bending a motor mount on every bad landing!

[Jonny Retro]

That's some really ambitious & spectacular work

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

I did notice the characters on the right rear arm though - sorry !