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Wheel_Nut

Build Thread: Wheel Nut's 2WD Truck using a Lunchbox gearbox

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I've made a few changes as I wrote yesterday.   The FR4 plate that goes under the front axle has also been remade to space the Panhard-rod further away.  Its still a tightly packed assembly.   The only possibility for contact now is the bell-crank against chassis rails in the combination of full steering lock with the axle fully articulated in roll.   I will need to trim the chassis rails by about 3mm on the the lower flange.  I will also add a spacer under the mount for the front shock tower to gain more clearance there.

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Absolutely stunning work. I wish I could do stuff like this. I can only admire from a distance.

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Thanks for the positive comment.   Its good to know someone is interested. 

With model cars there so many opportunities for fabricating custom parts.   Some aspects are similar to full size cars, but its much cheaper and a lot fewer troubles.

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COming on very nicely! Interesting arrangement with the steering tierods. A DT-01 bellcrank could also work perhaps, while giving some Ackerman?

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Wow, truly stunning work, very inspiring - I have been doing a lot of work with 3mm alu sheet recently but I'm starting to think more about FR4, simply for weight reduction.

I have never drawn by hand (apart from very rough not-to-scale sketches) as I completely useless with a ruler, however I am teaching myself CAD for more accurate prototypes with the possibility of manufactured parts later.  Currently I'm teaching myself parameter-based design so I can easily revise a design just by changing a single parameter and letting the rest of the dimensions work themselves out.  It's been a steep learning curve but there's loads of detailed tutorials out there for Fusion 360 and just recently I've been able to knock up a set of Clod TVP chassis plates in a lazy afternoon.

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9 hours ago, TurnipJF said:

COming on very nicely! Interesting arrangement with the steering tierods. A DT-01 bellcrank could also work perhaps, while giving some Ackerman?

Thanks for the suggestion.   I realise the tie-rod connection isn't great, so I'm thinking about alternatives if ever move to a version 2.  For this chassis I probably won't change except if and when it breaks.

The Ackerman doesn't seem to be an issue.   Since the bell-crank is located very close to the axle, when steering is applied, it moves both tie-rods into a more oblique angle which creates the proper Ackerman.

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23 hours ago, Mad Ax said:

Wow, truly stunning work, very inspiring - I have been doing a lot of work with 3mm alu sheet recently but I'm starting to think more about FR4, simply for weight reduction.

I have never drawn by hand (apart from very rough not-to-scale sketches) as I completely useless with a ruler, however I am teaching myself CAD for more accurate prototypes with the possibility of manufactured parts later.  Currently I'm teaching myself parameter-based design so I can easily revise a design just by changing a single parameter and letting the rest of the dimensions work themselves out.  It's been a steep learning curve but there's loads of detailed tutorials out there for Fusion 360 and just recently I've been able to knock up a set of Clod TVP chassis plates in a lazy afternoon.

Some areas on this truck chassis would benefit from 3D printed parts.  With a few nicely designed bulkheads and plastic mounting blocks, the mounting points for the arms on the front axles could be better located and oriented.   The ball joints on the front axle are close to the maximum radius of movement in the orientation they are used currently, so that should be changed if its desired to get more suspension travel.   At least CAD should offer the ability to analyse any clearances and interference issues at the design stage.

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Today I made the sway bar for the front.    I haven't done this before, but I calculated the stiffness for the bar and hopefully it will work.   Without the sway bar a rigid axle tends to roll more easily than a independent design.   A firm front sway bar is intended to help the traction at the rear.   The sway bar is being painted now, and will be installed along with the front shocks tomorrow.

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On 5/1/2020 at 12:23 AM, Wheel_Nut said:

Thanks for the positive comment.   Its good to know someone is interested. 

With model cars there so many opportunities for fabricating custom parts.   Some aspects are similar to full size cars, but its much cheaper and a lot fewer troubles.

It's hard not to be interested! 

I just wouldn't know where to begin with something like this, even the initial drawings etc. It's very impressive from my point of view! I've done a few basic things like recreating shock towers etc but designing things from scratch like this, I just wouldn't have a clue. I have a few 3d printed mods and some stuff that's had lathe work but really I just had the vision, I had to rely on kind friends who knew what they were doing to actually realise the ambitions lol.

I can't wait to see this in action.

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For this truck the inspiration came from Hotrods.   I wanted to design a retro-tech suspension such as the rigid front axle and see how it performs.   I also can't wait to see it in action!

 

 

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Very nice . I made some F&R sway bars for my modded LB's , it does help and they look good too .

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To fit modern wheels with 12mm hex on the Lunchbox gearbox, I'm using the Tamiya #53913 aluminium wheel adapters.   When fitting CC-01 wheels I found the 4mm Lock nut would not adequately thread onto the shaft and it was not a secure fit on the drive pin.   I decided to drill out the step in the bore of these adapters.  Now it fits like I'd expect it to.

 

 

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The front shock tower has been cut from 2mm FR4 material.  It couldn't really be any simpler with only 4 holes.   I originally planned to tilt the tower back slightly, but with the shocks mounted I found that vertical fitment was the best.  Next I will make some brackets to attach the body posts to the back of the shock tower.

I built up a second set of shocks that are identical to the rears.  These are Tamiya #50520 CVA short shock set II.   I used the 3-hole pistons and the supplied damper oil.   Tamiya supply two sets of springs, so I used the softer pair with spring rate of approx. 34g/mm.  These are softer than the Lunchbox kit springs.  I added a 3mm silicone bump stop on the shaft.  Fully compressed length is 62mm, and fully extended is 87mm.   The front sway bar has been fitted and it seems to be nice and firm as I hoped for.

 

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Here is my attempt at building a battery mount.    To keep the battery in, the plan was to use re-fastenable cable ties.    There are probably better ways to do it.

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Front bumper is now attached.   It uses a plastic bumper molding from the TA-05 "B Parts".   I used the body posts from the same sprue.

The FR4 plate to attach the bumper is bolted to the chassis rails via a 6mm thick piece of plywood used as a spacer.

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I think all good custom builds need a bit of plywood in them somewhere

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On 5/19/2020 at 11:00 PM, Mad Ax said:

I think all good custom builds need a bit of plywood in them somewhere

 I got a laugh out of your comment, but its true.   The entire chassis rails can be made from wood if it has aluminum reinforcement in the places that take the highest stress.

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The truck has been finished off in the last few days.   A new 2.4GHz FHSS receiver was added, with my ancient Mtronics ESC that I last used in 2006.

I took it to my local park for a run.   It seemed quicker than I expected from the standard 540 motor.   More rear grip would be a help.  On ashphalt the handling is precise and responsive, but it has some rear-end hopping under power on rough surfaces.   I'm unsure if its torque reaction lifting the suspension, or just due to the un-sprung weight of the motor.    I'll try to post a video next time I run it.

 

 

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I could lower the body, but the tires would rub at full compression.   I'm thinking about changing the wheel and tire setup for something bigger and softer.  I will run it some more before I make a decision.

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1 hour ago, Wheel_Nut said:

I could lower the body, but the tires would rub at full compression.   I'm thinking about changing the wheel and tire setup for something bigger and softer.  I will run it some more before I make a decision.

Reduce compression by adding rubber tubbing on the damper shafts.

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