Super Falcon

[ThunderDragonCy 8127]

1 hour ago, BuggyDad said:

Bit of a session on the shocks. I've fitted 42mm shafts on the front and 54mm on the rear. 11mm or so of rubber tube spacer each end to prevent shaft ends hitting the diaphragms and now also short eyelets in the front. This retains comfortable chassis bottom-out but adds down-travel. 

On the front I now have 21mm (front of tub) ride height plus 6mm of droop, which is close to the max (maybe there's another 2mm to be had with a perfect length eyelet) wheel travel available with these shocks. On the back, ride height 21mm plus about 15mm of droop if I want it (which I don't if I can't have it in the front and anyway I think it'll create crazy weight transfer) but I haven't got around to limiting it because I'll want to change the shafts again. 

The 54mm rear shafts are no-name Chinese and are ill-fitting around the piston, but they're also unnecessarily long, so I need to hunt for some good ones around 50-52mm.

Then I reduced the rear damping. The piston holes are relatively very small at 3x1mm so 100 oil is now in to compensate. I guess if I had the right drill bits I might refine that way but I don't there's much point at the moment. I'll cross that bridge only once everything else is about right if I then feel the need. 

Ooooo love a bit of puzzling. I have been right into this recently too. Couple of suggestions:

For 2mm front eyelet extension, 54871 gives you reinforced short eyelets and some plus 2mm options. Has helped me get my FF01 right 

For rear shaft, check the buggy damper thread, but i am fairly sure the df03 shocks use the same long shafts as the cva1 long damper which are over 50mm long. Check the boomerang or df03 ms manuals. That should be the part number.

3x1 won't be enough on buggies i suspect. Been trying to work out hoke sizes for my shocks on Ultra G EVO. The trf 10mm buggy pistons are 2 x 1.4mm front and 2 x 1.3mm rear. The area of the 1.4 holes is 3.1mm2. 3 x 1mm holes is only 2.35mm2. You need to open those three holes out to maybe 1.2 to get something similar.

[BuggyDad 5396]

1 hour ago, ThunderDragonCy said:

Ooooo love a bit of puzzling. I have been right into this recently too. Couple of suggestions:

For 2mm front eyelet extension, 54871 gives you reinforced short eyelets and some plus 2mm options. Has helped me get my FF01 right 

For rear shaft, check the buggy damper thread, but i am fairly sure the df03 shocks use the same long shafts as the cva1 long damper which are over 50mm long. Check the boomerang or df03 ms manuals. That should be the part number.

3x1 won't be enough on buggies i suspect. Been trying to work out hoke sizes for my shocks on Ultra G EVO. The trf 10mm buggy pistons are 2 x 1.4mm front and 2 x 1.3mm rear. The area of the 1.4 holes is 3.1mm2. 3 x 1mm holes is only 2.35mm2. You need to open those three holes out to maybe 1.2 to get something similar.

Ah ha! Thanks! Very helpful on all counts. 

Great shout on 54871 which I already have a set of, bought mainly for spare top caps and spring stays for my DF-03 aluminium shocks, so I could nick eyelets. 

Found the DF-03 MS manual - rear shock shaft is 9808076 but is out of stock everywhere. However, I have a set of these shocks so can measure and then find an alternative, and I dont need that exact length so should be able to find something. 

I'd better buy some drill bits. Thanks for reminder to calculate total area. If I take a new blank then a 4 hole pattern is also available. I do get the feeling that you can't just go softer and softer on the oil to make up for too small holes - it's already behaving slightly different to expected, like resisting the initial hit a bit too much. Perhaps this is the same concept as "pack" but taken too far. Maybe a bit like you can't just go harder and harder in the oil to make up for leaky CVA pistons. It just doesn't seem to quite work that way. 

Long term, when I come back to this when other projects are finished, I may look into designing a carbon front shock tower to take short shocks - with a 42mm shaft and smallest eyelets, I think they'd give quite good travel (~8mm more than minis) without towering up too tall. 

In a couple of days I pick up a used Blitzer Beetle to turn into a Stadium Blitzer but with my Falcon mods, so I'll be taking a lot of this on to that also. This time I have RcAidong steering, which looks the same except adds another pair of bearings (bridge). 

[ThunderDragonCy 8127]

@BuggyDad Glad that was useful. 4 x 1mm holes would give you about the same area as the 2 x 1.4mm. I know what you mean about holes vs oil. There must be some science, but i borderline failed both my fluid mechanics modules! 

[BuggyDad 5396]

1 hour ago, ThunderDragonCy said:

@BuggyDad Glad that was useful. 4 x 1mm holes would give you about the same area as the 2 x 1.4mm. I know what you mean about holes vs oil. There must be some science, but i borderline failed both my fluid mechanics modules! 

You and me both. I'd forgotten there was a second. Maybe I erased it from my memory in an effort towards mental self-preservation. 

[BuggyDad 5396]

The Falcon got a little run today on a tarmac pump track. Bit much for it but no significant damage and the shocks damped the landings very nicely actually, considering the lowish amount of travel in the front. I still think its sweetspot is to add just a bit more droop to the front, limit the rear so it's similar, and don't see it as a jumper like this, rather more for old school running with only smaller jumps. 

It's got a lot of acceleration, with its 8.5T motor and low gearing, or it would if the tyres could handle it, so I should dial the punch down. That motor is only in to generate decent top speed because of the low gearing. 

And I thought it handled pretty well, given it had odd tyres for the surface. One thing I noticed is how the front wobbles on a landing. I think it's deflecting a long way laterally and springing back, with the very flexible arms and c-hubs. I think its handling would really benefit from stiffer parts, which I could easily design, but they would also transfer impact force elsewhere of course, tough on the inner suspension pin to bulkhead area. One to mull over. 

[BuggyDad 5396]

On later (very brief) inspection I saw after today's run that one rear shock has zero damping. I don't yet know the cause but my non-standard x-ring sealing is a possible issue, which would be a real shame because I consider it such a worthy upgrade. It's not the only potential cause though - I hope it's the piston popping off the top of the shaft because of bad e-clip to shaft fitment on my cheapie shafts (3mm shafts but they take larger e-clips and the clip recesses are just a shade too close together for perfect settlement of the clips either side of the piston) which I'm going to change anyway. It'll be a couple of weeks before I return to the car and some tinkering time to find out though. Meantime I intend to order better fitting (and more suitable length) shafts from a reputable manufacturer regardless of this failure. 

[BuggyDad 5396]

So, as I'd hoped, the shock issue was the bad shaft/E-clip thing. I've replaced the shafts with good quality 50.5mm ones, adjusted the spacers to suit, drilled out the holes to 1.4mm (because 1.3mm was still a bit heavy on the DT-03 and I figure this is similar enough to that (rear arms based on DT-03 dims, similar weight distribution) and filled with 300 oil. I'll take that as my starting point for further damping adjustment, but so far it feels decent enough. Droop and travel now balance pretty much front to rear. Maybe I'll get a chance to drive it next week. 

If I get some new blanks I'll try 4 smaller holes. 

[BuggyDad 5396]

The Falcon went well on astro at Tamiya Junkies. Loads of running and it drove quite well in the main but gave me a load of ideas to mull over.

Once I got some suitable front tyres on it it was able to turn in well enough - the steering works well and the increased throw from my crank system is critical to this, although I suspect it could be improved a lot with suspension setup because it's heavily sensitive to front to back weight transfer and needs driving accordingly. 

The very flexible front arms were surprisingly less of an issue on the Astro than I expected, but I suspect they still make it very imprecise compared with something more solid. That said, they survived quite a few hits so the flexibility there is perhaps not to be sniffed at. Bearing wheels are a bit of a pain mostly because I want interchangeability, but also because I think I stand a better chance of finding something that looks right with hex. So I need to mull over whether to do a hex conversion (which would be easy), whether to design new arms, which is also not difficult per se but which might create an undesirable block/bulkhead weak point (or further highlight the already famous, but somewhat well braced on mine, chassis to Bulkhead fixing weakness). And just maybe to consider designing any changes into the mounting/bulkhead area (less easy) to preempt and solve those weak points.

However, right at the end of the day I broke the gearbox housing. It'll have been an impact at the rear wheel that did it, I'm pretty sure, and if I can brace the suspension mounts left to right in front of the arms (already done behind) that'd solve that. However, there's a question around how far to go with this gearbox, which is geared for truck wheels (so I run a very powerful motor just for the top speed - not an ideal solution) and offers no real diff options. So as I see it I have a few options...

The easy (assuming I can find room to do it) and cheap gearbox option is to strengthen the design I have and just run it. 

Another option is to fit a different gearbox altogether. With a combination of carbon sheet and a couple of 3d prints I reckon I could fit a BBX gearbox to it. That has many advantages:

- all the diff and gearing options I could want

- I use it on 2 other cars (and would nick the BBX's slipper - there's no need for a slipper on that) 

- 3 gear layout reduces squat (could have a really positive handling effect on this)

- I'd design it then to share rear arms and uprights with my homebrew Mohawk buggy

- I could, if I wanted, push the gearbox and arms back to extend wheelbase and improve weight balance

But that idea has the disadvantages that the BBX box is expensive and the change makes this Falcon even less Falcon. 

Which brings up a final option, which is to focus my work on the Mohawk as a sort of "platform", but shape a second chassis (or maybe even use the tub) around the Falcon on it, to create a new "Mega Falcon" which is really a variation on the Mohawk. I think with keeping the yellow CVAs it would still look very nearly as Falcon-like as this already does. This uses so few existing Falcon parts that realistically I might as well fix up the current one with the minimum option for the price of the gearbox sprue and some modding time and wait to make a new one until I've refined the Mohawk successfully. 

[BuggyDad 5396]

A bit of Falcon progress. 

If it wasnt already obvious how the gearbox broke (it was), it is now. 

Gearbox mold suspension mount wrenched out in a hit to the wheel from the front. So we can be clear that the inboard suspension pivots need left to right bracing both in front and behind the rear arms. 

Behind the arms I'd done already, and there's a recess for the skid plate mount which enables the brace to avoid crossing inside the gearbox seal. So that's great, we'll do that again. 

In front I had to go right through the gearbox, but I found a way to cut this fairly well (pillar drill for pilot holes at the ends of the slot, then use a 2mm drill bit sunk right up deep into the chuck so only about 3mm remains exposed, then use it as a sort of free hand milling machine, finish with knife. Result is quite tight, so it works even if it's a process with great error potential. Now I just have to do it three more times (two gearboxes to do), but I ran out of time.

Assuming I don't make any mistakes the result should be quite strong. I'll seal it with gasket compound. It's quite time consuming for little progress to show, but at least I've cut the four carbon braces I need for the two cars now. 

The option also exists to mount essentially the Mohawk back end to this, with a piece of carbon sheet under the gearbox to the rear of the tub, and a 3d print linking the top of the tub to the top of the gearbox. Suspension off the carbon sheet. I don't think it'd take that long actually, but for now I'm going for the Super Falcon as is, just toughened up a bit. 

The other car for this gearbox is the BB I bought off @Busdriver, which is to become a modified Stadium Blitzer, gradually taking on all my Falcon mods as and when, 3d printed body mounts and then a suspension overhaul. 

[BuggyDad 5396]

Got the Falcon fixed essentially as was, just with the extra bracing between the rear arms. That should make a big difference to its toughness, and although it's probably not the absolute best driver, I like it for what it is so for now it stays like this although I might print very slightly shorter arms for better outdrive/shaft engagement.

The brace cuts right through the gearbox but there's plenty of space there, forward of the diff, and I managed to cut it close enough that I don't think it'll let any crud in. 

I may also chop the wing section of the body off, it's such a weak point, and look for a way to mount wing to chassis. 

[BuggyDad 5396]

Falcon ran well again at Tamiya Junkies. I didn't run it that much because Mohawk is better and had had less time before, but I did get a chance to fit stiffer front springs so Super Falcon doesn't dive so much into corners, which is definitely a win. A little more to do just to refine around those (damping, plus do something to the rear to match, or find springs that are between my two options) but not too much. 

Then I damaged a motor contact in a tumble (they're very exposed) and that finished the Falcon's day.

I'm not sure whether simple solder will get me a lasting repair here. Maybe it will. I'll certainly try. How do I fix it otherwise? Can you get spares for Hobbywing Quickrun motors? 

I think then I will need to rotate the motor forward to hide the contacts from damage. I think I can make space by moving my turnbuckles to a different position. The sensor cable is also very vulnerable as is. 

Another thing I need to do is mount the wing to the chassis. The rear of the body is vulnerable and getting a bit of a beating, as is traditional with Falcons (and many other cars with body mounted wings). There isn't really a perfect place to screw a mount to but if I made a CF tower and my own mount for that I could incorporate wing mounting. 

[ThunderDragonCy 8127]

@BuggyDad i would un-solder all the plugs and attached the wires directly to the tabs. Stabld be fine then.

[BuggyDad 5396]

2 hours ago, ThunderDragonCy said:

@BuggyDad i would un-solder all the plugs and attached the wires directly to the tabs. Stabld be fine then.

I will have a look at that. In this case they're not really tabs like I've got elsewhere, rather it looks like a piece of circuit board material and it's that that's snapped. I still think it should be solderable and will give it a go but am a little wary. I might leave the others alone, or maybe I'll open it up to investigate further before I do anything. 

[BuggyDad 5396]

Designed a new rear tower section. 

It enables the wing to be chassis mounted and may enable the body to be dropped a few mm further. Slightly neater cable routing too. It necessitates losing the small rear most black section of body because that was the wing mount. And this will also need a new body anyway because it gets rid of the need for big tower cutouts and so this old one looks odd. But it will do as a runner. That's fine - I always intended to do a better shell sometime and I have one for the purpose. 

The tower is a 3d printed placeholder til I get my CF cutting going again.

The Eagle-eyed may spot a missing motor cable - still not tackled that.

[BloodClod 366]

This is another inspiring project! You do awesome CAD work and I love how the custom bits contribute to the buggy without changing it's essential character... That's a tight line to walk.

May I ask what printer you're using? Those arm prints look great and don't look like fdm?

[BuggyDad 5396]

5 hours ago, BloodClod said:

This is another inspiring project! You do awesome CAD work and I love how the custom bits contribute to the buggy without changing it's essential character... That's a tight line to walk.

May I ask what printer you're using? Those arm prints look great and don't look like fdm?

 

Very kind. Thank you. My printer is just a Prusa Mk3 and those are printed in PETG, so it's pretty run-of-the-mill stuff. The trick with the wing mount arms was about orientation. They are printed lying on their outboard side. This way they are strong but flexible in a downward bend and you get a nice presentable face looking from the side (textured printer bed helps I think, if you like that textured look for the face, and anyway it really helps with printability). The downside, if it is a downside, is that they're screwed to the chassis in line with the layers. I've tackled this by clasping them in a bracket printed in the other orientation and running screws through bigger holes, fixed with flange nuts. This way the screw isn't stressing the wing arms in their weak axis. And there's a side benefit of only reprinting the small part you break, rather than the whole assembly. At the wing this disadvantage applies again - there I've just beefed it up a little and will either risk tapping into the print or drill it out to take a screw and nut. 

The tower mount (the large piece in front of the tower) is printed with that front 45° face as its base. This way all screws (both vertical and horizontal) are 45° to the layers, none in line, so stronger. And again we get the base for our most visible face. 

It may not happen very soon but I look forward to painting and fitting a new body, in part because of the opportunity to lower it further into the chassis - the car could look lower still without any reduction in ride height.