So I've begun rebuilding a Fighter Buggy RX from my childhood...

[Lawsy 27]

Thanks mate - those are ball collars as well.

One of the front dampers are less "damperish". I've re-opened and ensured there's no air, sucked the oil out to remove tiny air bubbles, put the zero air bubble oil back, perfect silky oil.

Nope, no difference.

Thoughts?

[Nitomor 2122]

So there's our mission - come up with some de facto standard DT01 rear suspension improvement mod... Something easy enough for anyone with a set of screwdrivers to accomplish.

I find this improves the off road prowess considerably...

[Lawsy 27]

I find this improves the off road prowess considerably...

Very good, but what about for on road bashing?

I need the centre of gravity to be low enough for high speed on-road thrashing, and eventually brushless.

I do have an idea I'm toying with, requires some bodging up, but could work... Requires replacing the lower gearbox screw with quite a long piece if M3 threaded rod... Not quite sure about the rest yet but we're working on it (The biggest issue is dealing with motor wires actually - what do you guys do to keep them out of the way?

[GregM 1109]

I guess you had paid close attention on your damper yet. I'd check if there is any molding flash left, and if the piston plate matches the corresponding cylinder. In rare cases, a plastic part might be even warped from the factory.

The large wide heavy Mad Bull wheels help keeping lots of weight near the ground, thus lowering the overall COG even though the ground clearance is increased. Plus, they are slippery, so rollovers are less likely to happen.

Since this isn't an option for you, I'm curious what you've got on your mind.

I keep my motor cables away from moving parts using zip ties.

[Nitomor 2122]

For the first time I just put some heatshrink on motor wires on my GF01 build. It's not quite the right size so hasn't shrunk down in the way I had in mind but you get the idea! Both wires are pushed in to a central point on the motor and then exit together.

[GregM 1109]

Now that's a good idea!

Well, on the DT-01, Grasshopper and Grasshopper II chassis, the motor cable issue lies in how the motor is attached to an articulated unsprung solid axle gearbox. Thus, the motor follows all movement of the gearbox, instead of being fixed to the sprung main chassis.

This means that if you want the motor cables to be kept away from the rear wheels, you need to fix them somewhere on the chassis' upper damper mounts. But at the same time, you need to leave enough length tolerance for the cables to follow the suspension movement. If not, too tightly fixed cables will cause a malfunctioning rear suspension.

That is more easy with 2-pole connections, but once you've gone for brushless with at least 3 connections (plus the sensor cable on sensored systems), you need to be a bit more careful when routing motor cables. Also, the battery cable on the DT-01 comes out sideways and dangerously close to the wheels if not secured properly.

[Lawsy 27]

I've got a whole big post written up on my pc, just haven't posted it up yet.
I've basically solved the binding, used quantum theory to explain the rear dampers, and rocket science to attempt a front end geometry fix...

All the damper parts seem as they should, pedantry is certainly one of my more useful traits for this sort of thing (though sometime's my hyper focus will cause me to miss something obvious, so I'll go over it again). But what I certainly do notice is that even if I'm extremely careful, the problem damper almost always has tiny bubbles in the oil when I pull it apart again after a put it through its action a few times. I've rebuilt it 6 or 7 times now.
I even tested whether having the piston in various positions while you tighten the cap down (to induce a slight vacuum) to see if that what would help. Certainly having the stem at the half way point is much better, but still limited in solving the issue. It really feels like there's another very small hole in the piston.

The thing is, it all looks good, and the amount of tolerance in each part looks the same as it's corresponding part on the other side (the difference is around half the damping effect, so this should be visually obvious).
The only thing I haven't done is pull the o-rings.

I'm convinced it's the piston, or cylinder, because with the cap off just after filling with oil, pulling the stem down on the good damper feels like it should - well damped. The problem damper is easier to extend under the same circumstances. The bubbles simply don't help, and I think that's the thread, it feels a bit rough...

[Lawsy 27]

I also installed the steel pinion... I checked the mesh, it seemed fine - so why is it so freaking noisy? It's louder than the motor!

What am I missing? Noise is energy, energy caused by some type of vibration. Vibration can often mean abrasion, and that's bad.

Or is it fairly normal for steel pinion's to be loud?

[Lawsy 27]

Then again, straight cut racing gearboxes are loud as hel l, and they handle far more abuse for far longer than any street gearbox would, so maybe it's fine...

[GregM 1109]

The steel pinion should be module 0.8 metric pitch. Imperial 32 pitch will work within tolerances, but can be noisy depending on manufacturers. E.g. Traxxas pinions don't mesh well with Tamiya.

I'd recommend either original Tamiya module 0.8 steel pinions (they've been introduced in the recent years), or Carson Modelsport module 0.8 steel pinions (available through Tamico and some other German based dealers). I've had very good experiences with Carson pinions so far.

[Lawsy 27]

The steel pinion should be module 0.8 metric pitch. Imperial 32 pitch will work within tolerances, but can be noisy depending on manufacturers. E.g. Traxxas pinions don't mesh well with Tamiya.

I'd recommend either original Tamiya module 0.8 steel pinions (they've been introduced in the recent years), or Carson Modelsport module 0.8 steel pinions (available through Tamico and some other German based dealers). I've had very good experiences with Carson pinions so far.

Yeah it's a Tamiya, module 0.8. Got it with the dampers from Banzai (with a 17t as well).

Tomorrow I might make sure the motor is sitting square, checking if anything stuck to that motor insulator disc. A little angle could do it.

Or it could just be a noisy pinion...

[Lawsy 27]

Great job so far!

As you found out by yourself, acetone is destructive against some types of plastic, e.g. polystyrene (which is the material the Fighter Buggy RX bodyshell is made from, too).

For optimizing the suspension, I'd go for very thin damper oil and soft (but long) springs in the rear shocks. It doesn't hurt that the car will be sagging a bit when standing still, as this is rather a desired feature. Once you apply throttle, the DT-01 will get itself high up again anyway. Another thing that came to my mind when looking at your photos, you can go for ball mounts instead of straight screws or step screws. This will help with the weird 3-dimensional angles of how the dampers are mounted. I do not trust regular ball mounts for dampers, since the dampers may disengage on impacts or jumps. I'd rather use ball nuts with long M3 screws, or even better ball collars with long self tapping screws:

http://www.tamiyaclub.com/forum/index.php?showtopic=67074

It's not obvious from the photo's but those top rear mounts are ball collars #50591, which is how the machine thread is able to get through. I'm just out of M3 bolts so I can't do the lower points yet.

Fixing the binding issue.

From the front damper plastic parts tree, there are two small bump stop collars of different lengths that slide over the piston rod. To remove the binding, all that was needed was to slightly shorten the damper extension by using one of these collars internally, preventing the piston from bottoming out. I tested both, and the shorter one is fine. This is excellent as the extension is still on par if not longer than the friction dampers (but with the longer collar, the extension is reduced by around 2mm, as per the image below).

Now during use, any trace of binding has been 100% eliminated - less axle tramp is a good thing. And there is no downside since you still have maximum usable suspension travel.

This shot was taken while testing the longer collar (where you lose 2mm of travel to the friction damper), but now that isn't the case.

I've noted a few things with the rear end.

The standard friction damper has a tonne of pre-load compared with the CVA's - see the image above - it requires two of the larger pre-load collars and a small to get about the same.

Which is what I did for a while, but found this was still too soft and pushed the front around.

So I ended up with the CVA packaged springs and a medium collar on either side.

Regarding the front suspension

Once the rear was sorted, I could fine tune the front (I was testing various settings at each step of rear adjustment also, but on larger increments to see if I could remotely get the desired result). In the end, the inner mounting holes and a single (medium) pre-load collar worked best on-road, with these tyres.

If at medium-high speeds you back off suddenly and give it a Scandinavian flick, you will bring the tail around almost a full 180°, depending on your timing. It's quite nimble actually...

I think as well once the correct size rear tyres are on this thing, it will push slightly again, and that should be about perfect.

An incident with a tree... (written after the above)

So we went to a little park while taking the boy for a walk. There are these play areas with BBQ's, kids jungle gym and shelters on one side of quite a wide (5 metre) pathway. On the other side of the pathway about 1 metre in from the edge are special square holes in the concrete where a tree was planted years ago. There would be one every 4 metres I would guess - the trees are now middle aged and would have around a 200mm trunk...

I got too close to one while the car was around 30 metres away, and then I had a brain fart, resulting in this.

Argh... So there goes all my front end grip again as I wait for these replacement wheels/tyres...

[EDIT]

I used some "quicksteel" to rebuild the upright this time - JB weld just didn't do it for me last time.

My constant destruction of steering components has me thinking - is there a wider front bumper that would suit this thing? If I could get the impact of my inevitable crashes into solid objects to be absorbed by the chassis, then I could reinforce the chassis to cope. But I can't protect the suspension in the same way.

Any ideas?

[Lawsy 27]

I'm extending the rear-top damper mount a little to try and get the springs to actually resist roll, to do so requires them to be more vertical.

I went a little extreme with my first iteration, whereby the damper angle was very much like a Rising Fighter, but on the CVA springs this was too hard and bouncy. I was getting eaten by mosquitos and called it a day without trying the standard DT01 springs.

However, immediately going softer would defeat the purpose - hard is good, keeps the roll down, reduces understeer.

But bouncing is bad, so a hole might need to be drilled in the damper piston to soften it up a little... I don't have a thinner fluid and thinner fluid leaks more (these leak enough as it is, far out... I'm be rebuilding them every couple of weeks at this rate...).

The front end is still annoying me though, I want multi link without spending money, and this doesn't seem possible.

I might just go brushless as is then and if I destroy it by hitting a wall at 60km/h, so be it. Then I'll just get a DT03, or something I can recycle the electronics and dampers on...

[GregM 1109]

I think a rear stabilizer rod could help against the gearbox rolling to much under motor torque, while at the same time it will still allow the dampers to work.

Theoretically spoken. I think TA-Mark had once told that he had such a stabilizer setup, but unfortunately there were no pictures of it.

If you want a DT-03 for trouble free running, why not? A second car will free up your mind, while you could still trying to improve your Fighter Buggy RX when you like to.

But be warned, once you have added a second car to your collection, they'll soon start procreating like rabbits.

[Lawsy 27]

Yeah I've seen TA-Marks posts, and less than enthusiastic response to DT01 tuning. His swaybar pivot was mounted too high to be effective though. The combined rotation of both arms must be completely uninhibited. There should only be resistance when one arm is rotating opposite the other. Mounting the anti-roll bar so that it pivots around the centre of the suspensions geometric pivot is the only way to achieve this here.

There could be a really easy solution using the central gearbox pivot, we'll see...

I slightly stretched the standard DT01 springs so they remain captive in the CVA's. I did this through a combination of stretching all existing coils, as well as recovering one of the compacted coils at one end. The key is not to let the spring unwind as it stretches (otherwise the diameter changes, and that's bad). This way the rate remains about right (possibly even softens) with the added length.

The "rate" as felt when installed with the higher mounting position, and pressing down on the rear body mount, feels completely stock! Slightly more roll resistant, but not a huge leap, since the weight, as we all know, is unsprung back there.

On road at least, even with bumps, pebbles and rough joins in the driveway, stability is rock solid.

Being able to dial in a touch of static toe-out does wonders as well. It also means that combined with my reduced bump steer turnbuckle position, it doesn't spit itself sideways as soon as you land a little uneven. Also the CVA's and higher rear damper mount all but removed any of that bottoming out when reversing crap...

[Lawsy 27]

Right so here are some images of how it's looking now.

Comparison of high angle to standard

Here's what I've done

and

Here's how it sits

and compressed

Here's the stretched DT01 original spring on the shaft, holding the CVA spring next to it - I did botch the stretch a little but its barely noticeable in the rate, it just looks a bit uneven...

This was well worth doing. Here's a few notes/observations that must be considered though: -

• The more vertical the damper, the higher the effective spring rate (due to an increase in mechanical advantage, and corresponding reduction in suspension travel)
• I recovered about 2mm of this travel by using the slightly shorter bump stop collars on the exposed shaft
• Stretching the stock spring to just beyond the CVA spring length means it remains "captive" without collars, even at full extension.
• With the higher mount and stretched springs, roll resistance is higher than the standard mounting angle with CVA packaged springs and a thick pre-load collar - so from barely noticeable to "was there roll resistance now? Yeah maybe there was". So still crap all really, but it all helps

I really need harder wearing tyres for on-road use though, as this is getting pretty ridiculous, especially on the front... I have so much rear grip now that it just pushes the front around as if I am back using the standard, original pizza cutter front wheels and tyres! From a standard start, even on less than ideal surfaces, it just digs in and launches with not noticeable amount of wheel spin. My only concern is that this has increased motor temps a little (according to my "can I touch it" measurement methodology).

I'm yet to drill any holes in the dampers piston, but might later on still - using a thicker fluid is always advantageous for reducing leaks, so if I can soften the damper rate using the standard fluid, this is better than moving to a lighter oil...

I'm also considering strengthening the chassis in certain areas by bonding some 0.5 or 1mm nylon sheet to any flat surfaces with black sikaflex (the really good stuff). In particular, filling the grooves under the tub and covering that and the bumper with a thin layer of sikaflex and then the nylon sheet. Most really strong composites are bonded layers, so I don't see why this wouldn't be any different. The nylon will take a beating, and if I need to I could just bond another layer of nylon or fill any large gashes with sikaflex. It's the underside - so who cares what it looks like. I should not only get a more rigid, crash resistant chassis, but also lower the COG and improve the weight distribution a little where it matters - the sprung weight of the chassis.

Think about it - the roll centres of any suspension geometry are only effected by sprung mass. The sprung mass accounts for roughly half the mass of the car, since the motor and gearbox is unsprung. If we assume the sprung mass of the DT01 is around half that of the sprung mass of most other cars, then lowering the COG with the same weight in a DT01 will have approximately twice the net effect on the roll centre (inertial centres) as it would on the comparison car.

My point is, it might actually be worth doing since for a given weight penalty, I might be able to improve the COG twice as much as what would otherwise be possible and have little negative effect on total performance.

I might also consider running a bead of sikaflex into every joint on the chassis. You want the load to be born by flat surfaces, not joints - you can fix a crack easily (glue the piece back together, then bond nylon either side - stronger than new panel), but it's difficult to repair a joint. That's my experience anyway, hopefully it applies here. For a $5 tube of sikaflex, I've not got much to lose here.

Any thoughts?

[GregM 1109]

No thoughts aside from being speechless of how much passion, work and tinkering you put into your Fighter Buggy RX. To be honest, for onroad use I would have gone for a touring car, or a rally car chassis for onroad/mild offroad surfaces. Nonetheless you did a great job and I'm enjoying every post of this thread.

[Lawsy 27]

No thoughts aside from being speechless of how much passion, work and tinkering you put into your Fighter Buggy RX. To be honest, for onroad use I would have gone for a touring car, or a rally car chassis for onroad/mild offroad surfaces. Nonetheless you did a great job and I'm enjoying every post of this thread.

Cheers mate !

The sentimental value and the enjoyment my young lad gets from it drives this mini-project. He's only 5 months and loves it! I put him in forward facing front carry and he watches it zooming back and forth, flapping his arms and cooing as it gets close. It's adorable!

With the right wheels/tyres, I'll also find a setup that works off-road, but for now, bumpy driveway thrashing will have to do.

And I'm very much a tinkerer. I love karting, track days, most Motorsports, F1, Top fuel, DTM, Isle of Mann, Red Bull Air race (just thought of that, haven't seen it in years!), and I love good engineering - EPIC engineering especially. Stupid things like a great TIG welding jobs make my inside engineer smile...

I've also threatened to get the old Fighter Buggy out plenty of times before, but was never all that serious. Having a son however, gave me the motivation to dig it out.

And now I'm invested - getting a new gearbox and gears, the metal parts bag, and all that cost enough that I can't bail on it now, even if the suspension is really starting to pis s me off (especially the front). I take solace in the fact that all of the "good bits" can be transferred to a DT03 if/when that ever happens (likely the day I go brushless, and put this into a barrel roll immediately before impacting a solid structure of some kind). So the CVA's (assuming they survive the impact), the steering links and Traxxas carriers should be workable, the steel pinions, my old school FM radio from the glider I had, and of course we can't forget the cause of the accident, any future brushless motor I stuff in this thing. I'm also eyeing up a SkyRC S60 charger. It seems about the best way to get the "Genuine" iMAX B6 internals in a charger, which then opens the door to Lipo's.

At which point I've spent far too much money on this stupid thing, so much so that I can't not have a remote control car of some kind to make use of it all...

So I best get to the hardware store tomorrow and get some Sikaflex and see if my theory works or not regarding the centre of gravity improvement, as well as drill a single 1mm hole in the rear damper pistons (am I crazy doing this? I can simply use a thicker fluid if I had to revert back, right? Though I really don't think I'll need to.).

To hel l with it - I'm quite possibly going to order a 3930kv brushless motor tonight. The beginning of the end people, its arrived. Then come my Feb payday, Lipo's.

I'm going to go watch TV for a bit to try and stop myself from hitting eBay; give myself a bit of time to think this through sensibly....

[Lawsy 27]

Watching TV and thinking about the uncontrollable carnage doubling the speed of this thing only made it worse... 3930kv ordered (The madly cheap, prone to melting SkyRC leopard combo). I might even investigate the possibility of hiding another 2 cells somewhere...

I purchased an aluminum heat sync while I was at it. It might help, it might be pants, but for 3 bucks it can't hurt to try it...

I can't wait, haha!

[Lawsy 27]

I still don't have a matching set of tyres.

Any recommendations? Tyres are one of those things that I can't find a truly clear cut answer to. The Carson all terrains are expensive to get to Australia, and dirt hawgs don't come with rims, which is the bigger problem (I can't re use what I have).

Suggestions? I'd like rims with more offset on the rear especially, so I have the widest track possible, and my preference now is 12mm hex all round so I don't need to change turnbuckles and carriers.

I also don't want a diameter larger than 90mm (dirt hawgs the exception at 92).

I've trolled ebay enough to know wheels and tyres are a pain in the *******...

[GregM 1109]

The preglued Carson All terrain tires do not come with foam inserts. Plus, the wheels are brittle and thus prone to break. The tires themselves emit some nasty reak for a few weeks or months once unpacked.

I'd rather go for quality rear tires. The fronts, oh well... I think the less narrow ribbed DT-02/03 front tires do a good job onroad for starters, but they need 2.2" wheels, e.g. from the Sand Viper or Desert Gator.

[Lawsy 27]

Well the cheap ebay wheels crack the instant you breath on them sideways, but the tyres grip like turd on a shovel (and wear like 40 grit on balsa wood). They're also 31mm section at the front... Significantly more than anything on 2wd Tamiya buggy (that I can find).

But rims without toughness just won't do.

Maybe I'm searching for the wrong thing. Maybe just searching for 2.2 wheels will lead to better results...

[Nitomor 2122]

Goodness, you don't work for Lotus by any chance? Lol.

I thought I was guilty of over thinking things but you take that to a whole new dimension. Whatever you do, don't buy a WT01!! In fact, please do!

I started stripping my sons Mad Bull to clean it up yesterday because his science teacher asked him to look at how gearboxes work. I'm tempted now to dig out my fighter buggy from the garage and give it an overhaul, also tempted to try grafting the fighter buggy gearbox onto a Hornet and see what happens but that's a whole other project!

Good work, I have enjoyed reading the thread, shame the pictures don't show up for me though. Have you ever tried photobucket for picture hosting? It's really easy to use, even with Ipads and the like.

Btw. WT01 wheels have a shallow offset which will increase track they are 2.2 rims however.

Cheers

Nito

[Lawsy 27]

Goodness, you don't work for Lotus by any chance? Lol.

I thought I was guilty of over thinking things but you take that to a whole new dimension. Whatever you do, don't buy a WT01!! In fact, please do!

I started stripping my sons Mad Bull to clean it up yesterday because his science teacher asked him to look at how gearboxes work. I'm tempted now to dig out my fighter buggy from the garage and give it an overhaul, also tempted to try grafting the fighter buggy gearbox onto a Hornet and see what happens but that's a whole other project!

Good work, I have enjoyed reading the thread, shame the pictures don't show up for me though. Have you ever tried photobucket for picture hosting? It's really easy to use, even with Ipads and the like.

Btw. WT01 wheels have a shallow offset which will increase track they are 2.2 rims however.

Cheers

Nito

Haha, cheers.

For the pictures, you just need to click the links, they're publicly shared.

What's wrong with the WT01? Send me one and I'll see what I can do

I really haven't done much to this thing, yet... Nothing irreversible anyway.

I've got another idea. I'm waiting on some M3 threaded rod, this will go straight through the lower bolt hole of the gearbox. Then I'll fab up something to join the new rod and standard mounting point to allow the bottom rear damper position to be lowered and widened (this is the new part) so that its action is axial (damper angle doesn't change by much as it compresses). This will look a lot like a piece of Meccano, except aluminum, not straight, and holes spaced according to what I think will work best. The top does not need widening so much.

If this is possible, then it might help increase the roll resistance without additional anti-roll bars (and this should be easier to do). The trouble is the top mount, the rotation of the damper (or its axis of freedom) needs to be orthogonal to standard for this to work...

But first, tyres. I really desperately need wheels and tyres.

[XV Pilot 1936]

Haha, cheers.

What's wrong with the WT01?

Nothing really - in stock form with the stock motor it runs well enough. However it is an amazingly flexible platform for those who like to tinker, with many opportunities for modification and customisation. Probably a chassis you'd enjoy owning and modding?