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BuggyDad

BBX Wideboy

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I thought worth a build thread on this because I intend to do some different stuff. So I probably won't detail stock build steps much, because others have already done a much better job of that than I would. Instead this is about where I diverge from stock.

Essentially, I love the appearance of the BBX, which has really grown on me, and that it seems superbly executed in terms of materials and ability to take modern power. That's all a slam dunk. I also like Tamiya's decision to keep its driving style in keeping with its classic looks, but - I'm thinking about a bit of a divergence on how it drives. Why? A big part of the reason why is not that I believe I can do "better" (I most certainly don't), rather simply that doing this kind of thing is what about RC I enjoy the most and I have some ideas for a different take on this buggy. Tinkering, experimenting, modifying, finding my own way if you like. Totally subjective. On this I'd like to make mine wider, maybe lower, less rolly. This'll have to change its appearance a bit but mostly I'd like to minimise that. Oh, and the changes I hope to make should all be reversible so they'll be more of a set of experiments into changes I can make and what they do.

First, though, I'll build it stock(ish).

First evening's progress:

 

20231106_231834

Stock thus far except: slipper clutch, plumber's grease on the ball diff (which does indeed feel reasonably stuff, yet smooth. I also sanded the plates), 23 tooth pinion. 

I'm liking the quality materials etc so far, and especially the big ball joints which should make for sturdy and long lasting parts I reckon. Wee bit wary of how much it seems the flexy plastic cage is doing in structural terms to hold various suspension parts on. 

Electronics will be Tamiya TBLM 10.5T motor, 10BL120 ES, Savox 1252MG servo. 

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Fitted front arms and uprights this morning. I must say the quality of these parts is far superior to any previous tamiya I've built. Someone said it feels like Kyosho and especially for the front arms and uprights I'd say the same. Also on their use of ball joints to make caster adjustment easier but camber adjustment more difficult, I'm not sure that's such a bad thing. I'd like to mess with both, and once I settle I'll leave it, so does it matter? Not to me I don't think, and it looks oh so neat. The front arms are a lovely shape, and the material feels very tough. I intend to 3d print different ones but 1) I will not be able to avoid a significant downgrade on the quality of material and 2) where I previously expected to print them for hinge pin c hubs (mainly so as I'd only have to print lowers), I might now consider ball joints to keep these uprights and closer to this aesthetic. 

P. S. Sorry about the massive font up there. Dunno what that's all about! 

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Chassis complete except electronics:

20231107_193707

I love how it looks cage only with the chrome pepperpots. Wheel diameter is down a bit less than 10mm from stock but I think proportions look OK. 

No elecs because I haven't got a soldering iron with me and anyway I want to mull over wiring. This deserves a nice job, I think I want to use black motor wires and I think my ESC's battery wires aren't long enough, so I'll likely end up replacing all five, all black, just a bit of red heatshrink to identify polarity. 

I was going to complete it and run before any mods but I might whip off some parts now for detailed measurement and begin modelling alternatives for 3d print. 

Anyone who dislikes flex in a shock tower would probably take issue with how the rears are mounted to the soft cage, but is it an issue really? Gut feel is not for me. Maybe it's a benefit even? And it could be stiffened a little with some aluminium threaded standoff between left and right. I don't love the ball then nut at the rear shock tops (bad tool access) but equally I don't think it's a concern, just not a pretty or neat solution. And if I did go for an aluminium brace there it'd most likely have screw heads on the outside, losing the nuts. 

I put all my rear axle spacers inboard to head off swing shaft pop outs at the pass. There's loads of room for that, nowhere near binding. 

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I gotta say, that looks really good without the body panels on.Nice choice on the rim/tire combo too.

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1 hour ago, yogi-bear said:

I gotta say, that looks really good without the body panels on.Nice choice on the rim/tire combo too.

Cheers! Yeah I looked at it in silhouette and wondered why I hadn't seen it photographed that way before.

20231108_002704

 

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First method to consider for widening the rear is simply to add 10mm to control arms and swing shaft, space the swing arm's front ball joint out by the same and space the shock top mount out by the minimum required for it not to foul anything.

10mm because TD2/4 CVDs are +10mm, I have them, and they fit. Well, near enough - same joint design but different axle lengths so use the BBX axle. 

20231108_082156

BBX top, TD4 as stock bottom. 

20231108_124921 20231108_125056

BBX left side +10mm, right side stock. 

This enables the stock swing arms to be kept which is a major advantage. New ones would be relatively complex to model, probably require a couple of prototypes before I get the size and angles just right, their strength is critical and also they're quite large so pricey to print. It also means the wheel is only as far out relative to the swing arm ball joint as stock, so the movement of the arm and the forces on it are changed little. In fact, the longer control arms will make a straighter up/down path in the left/right plane. 

Although it feels solid, the standoff would put the soft cage under some nasty forces in an impact, so I'd want to design a better swing arm pivot point. I'd also need to cut the shell in a bit of an ugly way I think. And brace the top shock mount points (easy, but limited in its effect), or do something different up there. 

At the pivot point, I think I could design a decent brace to the three nerf bar screws, Spacing the nerf bar out maybe 5mm. Then if needs be I could also brace the top one left to right across the chassis with more threaded aluminium spacer tube. 

Quite a nice option I think. I reckon I can mitigate all the downsides except a rather agricultural hole in the body. On fitting, I note again how much room there is in the drive cup. I think it may work better at say 8-9mm than 10mm, which is a positive for this solution because it slightly reduces the downside of how much extra force is applied at the pivot. 

So for now I think I will pursue this and shelve the idea of designing my own swing arm. 

On the body, maybe I can space the side out just enough to limit the effect on appearance. Dunno. That's for another day. 

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Certainly got an idea in sight here. The old grey cells have been grinding away while I pretend to work. 

An option to brace the pivot to the chassis but also to stiffen the top shock mounts and space out the nerf bar, hopefully also help space out the body just enough to reduce cutting (not sure about this bit, needs a test fit of the bonnet section also) is to link them all together with a piece of CF sheet. I'd be happy to take a 7mm standoff off that for the pivot. It's not very pretty, it's an aesthetic trade off, but it would be mostly hidden behind body work. It's also all doable from the parts bin and would hopefully complete the rear widening job. No 3D printing required. 

20231108_162308

 

Everything above the top nerf bar screw will be exposed, almost everything beneath it won't. 

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Looking at options for widening the front, I designed a lower arm to take Dirtmaster C-hub and upright and use a turnbuckle above. Easy enough to model, and I have all the other parts. And DM C hub is in itself +10mm, so arm length can be unchanged, meaning leverage ratio on shocks is also unchanged. Fewer variables than expected. And my Falcon wants to nick the BBX's tie rods. 

But I hit a stumbling block. DM C hub height pivot to pivot is 25mm, BBX 30mm. 

So if I use the DM c hub on my BBX I run the risk of my negative camber reducing through suspension travel, which feels very wrong. 

The reason to use the DM parts in the BBX is because to widen it I have to design new arms and I was thinking I could just design bottom ones, with turnbuckles for uppers. Only 1 pair of arms = half the modelling and 3d printing, but also I'm a little reticent about modelling the ball joints - the points of interface are critical and there's a lot more to get wrong in a ball socket (entry diameter as well as ball diameter, plus the need for the material to take the stress of the ball being popped in). So it looks like my options there are:

1. to model a new c hub alongside my new lower arm. Easy enough, but still needs printing, although expect cheap enough. Kind of misses the point of just designing one part to slot in standard stuff I now have in, but it's still very doable and cost increase probably only c.£10. Also, I could model in some increased caster angle - need to learn about that but I saw something to the tune of "more is better". 

2. to model new ball joint upper and lower arms and keep the other BBX parts. This is perhaps the nice solution retaining the most essence of BBX, but there's more to print and I expect some trial and error on the ball sockets, so it might be twice the money twice over, or worse. If I don't do this I might model a simple dummy ball socket anyway alongside my other prints, so I can refine/learn the dimensions for minimum cost. 

3. to find a taller c hub elsewhere (but none of my other options in the buggy front hex conversion thread look tall) 

So at the mo I'm favouring option 1. Plus modelling a dummy socket for 7mm balls, a mount for my Hobbywing switch and just maybe some sort of wing mount (I think I fancy it low and right off the back, but I may be able to mount a wing with just screws and spacers to the rearmost cage joint). 

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1 hour ago, BuggyDad said:

Looking at options for widening the front, I designed a lower arm to take Dirtmaster C-hub and upright and use a turnbuckle above. Easy enough to model, and I have all the other parts. And DM C hub is in itself +10mm, so arm length can be unchanged, meaning leverage ratio on shocks is also unchanged. Fewer variables than expected. And my Falcon wants to nick the BBX's tie rods. 

But I hit a stumbling block. DM C hub height pivot to pivot is 25mm, BBX 30mm. 

So if I use the DM c hub on my BBX I run the risk of my negative camber reducing through suspension travel, which feels very wrong. 

The reason to use the DM parts in the BBX is because to widen it I have to design new arms and I was thinking I could just design bottom ones, with turnbuckles for uppers. Only 1 pair of arms = half the modelling and 3d printing, but also I'm a little reticent about modelling the ball joints - the points of interface are critical and there's a lot more to get wrong in a ball socket (entry diameter as well as ball diameter, plus the need for the material to take the stress of the ball being popped in). So it looks like my options there are:

1. to model a new c hub alongside my new lower arm. Easy enough, but still needs printing, although expect cheap enough. Kind of misses the point of just designing one part to slot in standard stuff I now have in, but it's still very doable and cost increase probably only c.£10. Also, I could model in some increased caster angle - need to learn about that but I saw something to the tune of "more is better". 

2. to model new ball joint upper and lower arms and keep the other BBX parts. This is perhaps the nice solution retaining the most essence of BBX, but there's more to print and I expect some trial and error on the ball sockets, so it might be twice the money twice over, or worse. If I don't do this I might model a simple dummy ball socket anyway alongside my other prints, so I can refine/learn the dimensions for minimum cost. 

3. to find a taller c hub elsewhere (but none of my other options in the buggy front hex conversion thread look tall) 

So at the mo I'm favouring option 1. Plus modelling a dummy socket for 7mm balls, a mount for my Hobbywing switch and just maybe some sort of wing mount (I think I fancy it low and right off the back, but I may be able to mount a wing with just screws and spacers to the rearmost cage joint). 

Option 4 - put an offset shock mount on your new atm so can you use the DM c hub? If the shock eyelet is 2-3mm below the centreline of the arm it would bring the end up 5mm? 

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25 minutes ago, ThunderDragonCy said:

Option 4 - put an offset shock mount on your new atm so can you use the DM c hub? If the shock eyelet is 2-3mm below the centreline of the arm it would bring the end up 5mm? 

The vertical position of the hub/upright is OK, it's the dynamics of it through the travel - basically if my top arm mount on the hub is too low, the top arm will swing out more as the suspension compresses, making camber change to the positive as it compresses. 

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Option 1 modelled. I can't be100% sure this'll work (haven't got the car with me) so I'm hoping to prototype it on a mate's printer. Fingers crossed....

 

Arm and c hub

 

I felt I had to beef it up a little - the BBX plastic feels really tough and the 3d printed stuff will be a significant step down. So my arm looks a bit ugly. One day I'll get better at the making it look good part of the design!

I'm not great at this. I suspect an experienced user would dispair at my process but I clumsily get there in the end. Not sure whether it's a software limitation or me as a beginner but I can't really move things around much once they're drawn, rather I end up deleting sections and starting them again. I need not just the dimensions before I start but to plan the process of drawing it.

As a little case study, a set of this (2 of each for left and right) in MJF nylon (strongest material I've printed) natural (cheapest) finish is <£15 plus delivery (and subject to a minimum order value). More than stock parts obvs, but not crazy I think. It's only occasionally you decide that a stock part or a bit of garage fabrication isn't the answer. Long way to go to minimum order value though, so I'd better get on the 3d printing/modelling to do list. Got a few little ideas.

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Don't put yourself down, that looks great! It took me a long time on 3D to start restraining the sketches in a way that allows you to moves things around. 3D does also require you to almost have the final part in your head when you start, so it's difficult to be really creative with it. I end up doing a lot iterations and totally different parts not based off the original in 3D if I am working towards a solution for something. The nice thing with 3D is that you easily overlay all these different idea parts on eachother to see what parts of which one work well. 

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24 minutes ago, cyclonecap said:

I don't own one but the new Arrma Gorgon has very chunky looking front hubs. They might be a good starting point for taller hubs.

https://www.modelsport.co.uk/product/arrma-gorgon-c-hub-set-1353898

https://www.modelsport.co.uk/product/arrma-gorgon-steering-block-1-pair--1354802

Good call. Anyone have an Arrma Gorgon they could roughly measure the vertical height between lower and upper pivots on the c hub? 

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Quick size prototype off a mate's printer is pretty good I think. My shock mount point is 1mm too far in. Measure twice and all that! But that's probably not an issue. I'll probably try different springs anyway. Total length is as intended (+10mm per side, to match the rear swing shaft difference when it's horizontal), range of movement looks fine. Good start. 

20231111_161341

Am I missing anything?

I'm considering designing in a pill shaped insert for the lower c hub pivot to offer caster adjustment (could also do this for rear toe on eg DT-03). Thinking about it I could also react to others saying the front suspension is a bit soft by adding a second shock mount, further out. Would that have the desired effect or would the more laid down shock counteract too much? Or would the more laid down shock offer desirable additional progression through the stroke even? 

I may need to space my turnbuckle forward or back a little to clear the shock but I figure that's OK and I haven't the means to confirm with me. It's not a definite, so it would only be a small spacer. Small chance I'll need to widen the top mount point but I'll take the risk, it's neater thinner. With the turnbuckle behind the shock, the pill to increase caster would help solve this problem too. 

I though the arm looked a bit clunky on the screen but I wanted that profile for strength. However in the flesh it looks quite well proportioned. 

It struck me also that this is now on TD2/4 CVDs and diff, so it's TD axle to axle at the back, although the axles themselves are slightly longer. So I expect it to be about 4mm wider than a TD in the end, if same wheels are fitted. 

From idea to prototype parts in ~24 hours. Could be much quicker. Amazing technology isn't it. And it could just as well be a finished part if I went straight for the commercial printers. 

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Perverse enjoyment from a Saturday evening really geeking out on the 3d modelling. Is this what family life does to us?

I started again with the C hub simply because the software was giving me all sorts of weirdness getting back into it and trying to hack it about, and I find that the basic shape is easy to model better a second time, I'm able to simplify or better approach the areas that turned into problems later. And I think I learned some tricks from finding different ways to do similar things 

I also wanted to add the pill insert idea, which would necessitate beefing up that area, and could see space to brace the spine of the "C" internally, which I perceive to be the weakest point. Now I'm pleased with how it looks.

Pill insert c hub

My friend's printer won't have the accuracy to do the inserts so I think we'll call this ready and keep the arm the same...  

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On 11/10/2023 at 7:44 AM, ThunderDragonCy said:

Don't put yourself down, that looks great! It took me a long time on 3D to start restraining the sketches in a way that allows you to moves things around. 3D does also require you to almost have the final part in your head when you start, so it's difficult to be really creative with it. I end up doing a lot iterations and totally different parts not based off the original in 3D if I am working towards a solution for something. The nice thing with 3D is that you easily overlay all these different idea parts on eachother to see what parts of which one work well. 

Thanks Cy, this is kind of where I headed. Although I haven't worked out how to test assemble different parts yet I'm going to research how that's done. Would be very nice to be able to do that. 

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Well well, the world really is your lobster with this stuff. Now I can check nothing fouls. +5 degrees caster, arm 30 degrees below the horizontal (the droop limit of these parts as currently designed) and it looks like the turnbuckle won't hit the shock:

Assembly 5 deg

Remarkable for free software, I think. 

I think I will also design something simple to brace my swing arm pivots across a width of the CF sheet, in place of standoffs. 

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BBX Side brace

Simple structure to spread the load of my now spaced out trailing arm pivots across CF sheet, in place of a standoff which if hit with a big side load would just tear out the CF. I'm so looking forward to assembling this car with all my mods, hopefully next week. It feels quite odd having all the necessary parts designed or acquired without it yet coming together in the flesh, only in the virtual world. It's not the shed tinkering that RC has thus far been for me but it's not less fun either, just different.

That said, inevitably this'll just be phase 1 I'm sure. It'll either all break, not fit, or I'll change my mind!

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Finally able to test fit my various widening mods to one side. Small steps, but I'm quite optimistic about where it's headed. At the rear it's all structure to deal with the effects of moving all the key points out 10mm. The carbon sheet braces all the low down mount points together, to the chassis and to the top shock mount, which stiffens and strengthens the package, and any loads at the trailing arm pivot are well spread by the braced stand off I designed to go there. In the main, that area should be stronger and stiffer than stock. New (to me) bench drill and a CF-specific jigsaw blade were a massive help in cutting and drilling the carbon sheet for all the mount points. And combining the slow moving jigsaw blade (compared with Dremel disc) and dust extractor nozzle clamped to bench is really effective for managing dust. 

20231119_224037

Top side is stock, bottom modded, so it looks weird but gives a comparison. I forgot to put the nerf bar back on the stock side. I would like to measure rear toe - it looks like a big angle both as stock and modded (they should be the same angles so it may just be perspective), and I could adjust it with spacers at the pivot. 

20231119_224901

Side on I don't think the big carbon brace/tower is too obtrusive. I guess it'll be more visible from some angles but also the body will help to hide it and the shock already does. 

I was going to extend it rearwards to incorporate a sway bar, hopefully down much lower than the aftermarket one, but having bought that I note it's too narrow to run through my carbon pieces, so I will either run it as intended (I have space) or bend a new sway bar myself. 

I haven't photographed the front suspension in detail but I think my new parts look good enough. Their movement is perfectly slop-free and they're stiffer than stock (not sure whether this is a good or bad thing), and appearance-wise I think you'd have to look very closely to realise they're 3d prints. However, required tie rod length is now really long, and there's a danger I've introduced bump steer as a result. One option is to replace the steering bridge with something that takes its tie rod ball joints outwards enough to keep the rods optimal length. The stock bridge has them together in the centre. The change is because I've gone from ball joint kingpin to an 11mm L-R distance from C-hub shaft to kingpin. We'll see whether there's a noticeable problem before worrying about solving it though. Anyway, a replacement should be easy to design and cheap to print, plus I have a load of other things to print soon.

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Pretty much there mechanically, for a first runner anyway. Still to do electronics and body. 

20231120_235853

20231120_235732

20231120_235641

Looking at the underside illustrates the mods I've done. 

20231120_235944

Everything fitted together as planned although I could've done with a third hand at times. Suspension movement is smooth and slop-free. After beng forced to use longer tie rods I had worried about steering geometry and thought I might need to make a new wider steering bridge, but it looks pretty decent - I don't think it'll need that.

Cosmetically, I'd very much like to bring the rear top shock mount points in and add some angle to the shocks, which I think I can get away with. Ideally I'd also bring the carbon in off the vertical, but I can't really do that because it sits against part of the cage half way up. Alternatively I could go for bracing only below the window, and find another way to stiffen the top shock mounts, which probably is possible, but I need to finish it with the driver figure and all the rest of it first to work out how best to do that.

Or there are some slightly crazy options buzzing about my head now. Widening the cage to make it a two seater?! Rally cockpit? Willy? Sort of "Super Wild One", although for all sorts of reasons that'd take some doing - I don't think it could be done using the stock cage sides and longer horizontals across, although in principle cage parts should be easy things to model for 3d print, since you can essentially just plot the key points, join them with lines and turn all the lines into cylinders at the flick of a button. Anyway, that's a dead end, I'm not going there (well, maybe a Willy figure). 

Another loony option is to make the rear shocks out of the way of the cockpit entirely with some sort of linkage to lay them down along the body sides. Suits trailing arm but couldn't be run off the arm the normal way (too much leverage) so would need some linkage. I'm not doing that either. 

To space the CF and nerf bar out is an example of a place where blue anodized aluminium is the wrong answer IMO. Should be larger outer diameter black plastic, but these are what I've got! Funny how you can be bugged my the smallest things.  

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I really like what you have done here!

Personal opnion though: I have a hard time un-seeing that the rear tyres look smaller in diameter (optical illusion) than the front ones. I guess it has something to do with how the cage sits in relation to the tyres. Or maybe it's just my old eyes. :D

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