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nowinaminute

I got a Lunchbox double wishbone conversion 3d printed for cheap, let's see how it goes!

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Far too many sharp corners in that design. When designing RC car parts you need to put little radii everywhere that two surfaces meet.
Sharp corners are great for giving way under stress. Heck, even making things out of metal when I was a maachinist you had to do that where possible.

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There is a 2mm 'tunnel' in the pivot of the arm which accepts the 2mm rod (after clearing out the tunnel from printing debris)

quote:-

This is the heavy duty wide or 8mm offset front suspension set. This kit has reinforced arms with a thin, 2mm wall throught the center of the arms and requires a 2mm rod to be inserted throught the pivot point and glued in place. The hole will need to be cleaned out using a 2mm drill bit before inserting the rod. Replacement arms are part number 070005-02.

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Ok I got a little footage. Typically for me, the one day I had any free time the weather went rubbish so I wasn't out long.

Instead of going to the skid pan (smooth leisure centre carpark) I went to the bone rattler (rough furniture shop car cark) the broken and scarred concrete and tarmac is a bit more of a test for the every day durability than the smooth stuff I have been using it on. This carpark can get the better of many vehicles, even much more sophisticated ones. The heavy pitting and ruts along with a surface that's constantly transitioning between slippery garvel and grippy tarmac can make even my best handling trucks flip over if I'm not careful so I thought it would be a good place to push it a little bit further.

I added a little negative camber now that I have the luxury of adjusting it and gave it a quick run around. It seems a lot more stable than before, It only tipped over once which I was quite impressed by. The fundamental handling isn't a world of difference on this terrain but it certainly feels a lot more planted and like the wheels aren't just flailing around randomly. It's better but it hasn't lost all of it's character by any means, it still has useless rear suspension and even with careful use of the throttle and the wheelie bar upside down, the weight over the front wheels is still probably only about 30% most of the time!

Please excuse the erratic camera operator. I've tried to explain to my daughter that smooth and steady is best but she feels that exaggerated movement is superior. Who am I to argue with someone who's best friends are a hatchimal and a cosmo robot? It's impressive that she managed to realise her creative vision despite the phone being mounted to a 3 axis gimbal.

 



Overall, it seemed pretty good and the replacement parts with solid infill are a fair bit stronger. I'm sure with more than stock power it would get a little bit crazy again but that's for another video!


Now, the two alternative options I previously alluded to should be up and running by next weekend.

One is courtesy or ThunderDragonCy, he designed a replacement cover/brace to enable DT03 arms to be fitted to the Rising Fighter but it hasn't been tried out on the CW01 yet, I shall be giving it a go very soon and of course there will be accompanying video.

Secondly, new member marks designed a very novel adapter that allows you to retain the stock A arm but still get double wishbone type suspension.

Both very different solutions to the same problem! I can't wait to try them out and get lots of video!

There could also be a redesigned A arm to replace the thingiverse one too, one that's better optimised for FDM printing.

 

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Slo mo shows the action of the front mod - it works well . Nice save from the potential roll over in the first vid. too.

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3 hours ago, KEV THE REV said:

Slo mo shows the action of the front mod - it works well . Nice save from the potential roll over in the first vid. too.

Hehe thanks, it hit the rut and started going but I managed to kill the power in time.

It does indeed seem to work well, I gave it some negative camber to help stability on this surface but I think it would have been ok with it more neutral tbh and It would have had a slightly sharper turn in too.

It would also probably understeer less with more weight over the front, it feels like the wheels were barely stuffing the surface whenever the power was on!

Very satisfying just to have it running without disintegrating at this point though!

More fun things to try this week, hopefully the weather is ok at the weekend.

 

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Cool . I put an old 540 motor and modelling putty into the front of mine in the void in front of the servo to keep the front down

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54 minutes ago, KEV THE REV said:

Cool . I put an old 540 motor and modelling putty into the front of mine in the void in front of the servo to keep the front down

I will definitely give something like that a go to see how I like it!

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On 1/11/2019 at 10:02 PM, smirk-racing said:

Where is that? Shapeways?

Sure is. I dont think I can post a link here though, usually it gets pulled. It is in the pumpkin section on my store, part number 070005-01. I needs a metal rod inserted along the pivot point

On 1/12/2019 at 2:37 AM, nowinaminute said:

I didn't realize it was a copy of your design, it seemed to be all angular and lacking reinforcements where the c hub attaches whereas yours is curved and has support in that area. The guy put up sets for the Grasshopper and DT-01 too. It wasn't me, honest! Please don't sue!

It did occur to me that reusing the stock bracket would be a much better idea and several other people have mentioned it too, I was tempted to just take the mounts off entirely and do exactly that.

I know the design is totally unsuited to the material, I don't know how to use the 3d software though, not sure I have the necessary grey matter to be honest :lol: seems like the person who came up with the file on thingiverse missed an opportunity to tailor the design more towards the intended print process, it could have been bulked up in certain places to at least give it more of a chance. It seems needlessly delicate.

I think a couple of guys on here are looking into maybe making a more suitable design for the arm. And there's also a couple of different directions I will be trying soon, with help from fellow members.

Saying that, the replacement parts I got with 100% infill are at least an improvement. With the breakages I had, a lot of those trouble areas were essentially hollow so not only a weak design but a poor execution too! The solid parts are at least holding up to casual use. I'm sure a better design would be beneficial though and even then, unlikely to be as tough as a sintered nylon.

 

Why did you disagree? Because you believe the part should stay flexible?

By the way, I sent you an email regarding Nikko F10 buggy parts in regards to your youtube video, not sure if you got it or not? 
 

Oh don't worry about it, it just means that I need to design better one (take a hint Tamiya...cough...cc01....cough). The reason I do not like the metal reinforced one is that it will simply cause a break elsewhere and as you say, it should be more flexible. I need to do an install video on that soon. 

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On 1/12/2019 at 4:35 AM, Pablo68 said:

Far too many sharp corners in that design. When designing RC car parts you need to put little radii everywhere that two surfaces meet.
Sharp corners are great for giving way under stress. Heck, even making things out of metal when I was a maachinist you had to do that where possible.

Exactly. look up de havilland Comet. 

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1 hour ago, Pintopower said:

Exactly. look up de havilland Comet

Oooooh you didn't just go there! :o:lol:

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Just to update you all a but,

The 3d printed system became quite usable once I had parts that were all 100% infill, I haven't thrashed it to badword and back but I got a good few hours of use in with no breaking so I think they could be a good choice for a budget option for when you're not bouncing the LB around like a football. I'm pretty sure they would lose any kind of fight with a rock or kerb, though!

The shock mounts seem to be the most dubious parts and I would recommend removing them and affixing the stock Lunchbox shock mount tbh.

ThunderDragonCy's replacement centre mount for DT02/03 arms works brilliantly, you get a wider stance with virtually zero arch rubbing even though the suspension travel is also hugely increased. With this mod you can use 100mm shocks and the chassis can touch the ground before the shocks bottom out.

4BxstPS.jpg

There's a little bump steer when you approach max suspension compression by that point it is so far beyond what the stock setup could do that I really don't consider it a flaw. If you limited the shock travel to where it didn't happen, it would still have more flex than stock.

I'm hoping for some dry weather soon to get some decent video, I added a little weight to the front of the chassis and it has reduced understeer a noticeable amount. On smooth tarmac at least, it feels very planted and stable at the front end (the rear ended is still hilariously useless though!)

I still have a mod designed by marks to try which utilises the stock arms, I'm waiting on some more threaded rod to make the links up before I can test it out, that should be here this week.

It's funny how I spent years daydreaming about better front suspension and here I am trying out 3 different methods in the space of a few weeks and they aren't even the most famous 2!

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3 hours ago, nowinaminute said:

ThunderDragonCy's replacement centre mount for DT02/03 arms works brilliantly

Thanks for the update . I'm glad you're getting some progress .

What is the DT arms centre mount ? , did I miss that write up ?

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On 1/13/2019 at 9:45 PM, nowinaminute said:

Secondly, new member marks designed a very novel adapter that allows you to retain the stock A arm but still get double wishbone type suspension.

I did try a prototype experiment with an original A arm which involved cutting off the top and bottom knuckle arm retainers from the arm and fabricating a 'C' hub and fixing it to the A arm . It works in principal but I need to do more work on it

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35 minutes ago, KEV THE REV said:

Thanks for the update . I'm glad you're getting some progress .

What is the DT arms centre mount ? , did I miss that write up ?

It's this item:

https://www.shapeways.com/product/GRSUZGQSU/tamiya-rising-fighter-grasshopper-2-4-bar-front

It might need some very minor modifications before it's a 100% a drop in part for the Lunchbox but it's 99.9% there already

fJtOaDU.jpg

Got some half decent video of it earlier, some on grippy tarmac and some off road. With the suspension setup and some added weight at the front, it wants to pull the tyres off the rims when you come off the throttle and turn hard! It still understeers somewhat on full throttle but much less and on part or no throttle it pulls in super tight AND it's still more resilient to body roll than it used to be. Very impressed!





 

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Very interesting . I'll look into that , thanks .This is a similar set up to the Kyosho Ultima front beam I tried out , I needed to fix it to the original LB front arms cover or something that I might make in alu. , it's similar but with a more abundant spares availability option than the Kyosho method , but I was curious to see if it would work . How much does it widen the front track ?

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4 hours ago, KEV THE REV said:

Very interesting . I'll look into that , thanks .This is a similar set up to the Kyosho Ultima front beam I tried out , I needed to fix it to the original LB front arms cover or something that I might make in alu. , it's similar but with a more abundant spares availability option than the Kyosho method , but I was curious to see if it would work . How much does it widen the front track ?

A LOT! I love it, need to make the rear match, it looks like a forklift truck or that bulldog from the Tom and Jerry cartoons at the moment :lol:

kboj3T9.jpg 

But I like that it gives more stability and the suspension can fully compress with little or no scrubbing. 

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WOW , that is wide . I think the dog is called Butch the bulldog - you should name your van 'Butch'  :)

Have a look at Nobbi1977 LB with a Madbull rear axle on it , it could match your front :-

https://www.tamiyaclub.com/forum/index.php?/topic/88602-i-said-i-wouldnt-but-i-did/

scroll down the page a bit .

On another note , I've managed to bolt the Ultima front beam into a mock up LB chassis , just need to bridge the gap where the original arms would have slotted in at the mid section and need to fettle the damper lower position a bit .Whether I complete this installation or not is another thing , just wanted some idea if it would work

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Here's some video with DT03 arms and hubs, bit of a rough cut but I need sleeeep.

Motor is now 20T btw.
 

 

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Looks good . Maybe some slightly stiffer springs on the front might stop the dipping on the sharp turns ?

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4 hours ago, KEV THE REV said:

Looks good . Maybe some slightly stiffer springs on the front might stop the dipping on the sharp turns ?

They are pretty stiff already, they are shocks from a Traxxas E-maxx.

The front has weight in it now for more grip. If I take the weight out, it doesn't dip as much but it understeers a lot more and is more bouncy off road too because the springs are too firm. It seems to be a juggling act but I'm quite happy with the compromise so far.

Worth bearing in mind that I was really trying to throw it into turns off the throttle too so the effect is exaggerated a bit.

The tricky thing is the weight is so biased towards the rear, it needs more weight at the front just to make it grip properly and then if you add sufficiently stiff shocks to stop it leaning despite the extra weight, the off road suffers because the suspension doesn't want to articulate.

I don't mind the leaning too much as long as it doesn't tip over though. I feel like it's a fairly good compromise between on and off road at the moment, I drove it for about 30 mins on the dirt being really ham fisted and it was much more stable than it used to be, especially considering it's only had the 27t silver can until now.

Perhaps some foam in the tyres could help though...

 

 

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