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Monster Beetle re-release #58618

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29 minutes ago, zakspeed said:

Not sure why there is a thing for placing the servo centrally, you lose the Akerman principle

Ackerman does not depend on the position if the servo. The only thing you lose is unequal tie rod lengths (and therefore unequal tie rod angles), which equals losing unequal turning circles - which is actually quite an improvement. The offset servo was never intended to improve steering. Those servos had to go somewhere, and there were two of them, so steering was compromised in order to place them neatly side by side. 

See the principle of the centralized steering servo and true Ackerman in action below, if that gif works... 

large.gif

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Hi Guys,

It seems that I need some help from all you Monster Beetle owners out there...

I spent my last two nights with my Beetle chassis assembly and finally it seems that I'm finished. I heard about the diff problems before so I went straight ahead and built the transmission with two 0.5mm shimms (Traxxas  No.:1985...). It was a tight fit, I bearly could screw the transmission side plates together but I don't want to have a diff problem during running in the future.

Now the diff action is tight but seems ok. It is as tight as when I turn one wheel, the other wheel and the motor spins with it and there is no diff action, but when I hold the other wheel the diff comes in nicely. Like a limited slipp diff. 

Now that the gearbox is now a bit wider, I had to take one rubber O-ring out from the right drive cup where Tamiya advices to put two of them because it was too tight and the trailing arm couldn't move freely.

I tested the car today morning but what problem I have now is that the right CVD and wheel shakes really bad at middle speed. Shaking stops when the trailing arms pushed up to a middle posotion and the CVD's are almost straight.

So could it be because the shimms are too tight? Or is it only the nature of the car?

Should I take one shim out to make the diff a bit loose? Every other MB owner seems to use two of them on each sides...

My problem is that it is a brand new gearbox and I know that it is a bit tight fit with the shimms already in but all MB gearboxes seems to get loosen with time and I wanted to cure the diff clicking in the first round.

I know that MIP diff is a way to go but I don't want to spend a whole lot of money on a new car...

Any advice would be great.

Thanks in advance,

Daniel

 

 

 

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The 2 issues are unrelated in my experience. Shimming the diff has nothing to do with the shaking of the dogbones. In running mode, the trailing arms are pushed up (static and dynamic weight transfer) and all is well. I'd say run it and see. I've shimmed the diff and never looked back.

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On 12/31/2018 at 4:48 PM, Saito2 said:

And to think, this was the chassis that dominated truck racing in the US until the conversion trucks began taking over.

I was pleasantly surprised by the MB when I built it a two years ago. For a 2.2 tire car/truck it was much quicker and less tippy than I anticipated. When I build a stock Blackfoot I will have to look at some of these light steering mods. Are there any recent threads that stand out as a must read?

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Thx for the help... Last night I deassimbled the gearbox and get rid of one shim so I only left one in the gearbox. The diff action is still stiff but way smoother now. Future will tell ;)

 

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Hmm, well, the mrs and I both built our MB at hte same time, both with shims. Hers was a bit notchy at first but has freed up, mine was silky smooth. Ran mine a couple of times, although the 13T motor I put in didn't work with tamiya ESC, so I put in another one, but it owuld then over heat, finally found one now that works with the 13T brushed.

 

Anyway, problem time, her dog bones drop out with very little provocation, even just full slack on the suspension they drop out. Mine had been ok, but then on the weekend I did a jump in the back garden, popped the dog bone too. 

It seems there are many suggestions, but I am going to try the simplest, I'll measure the length and take them down my local hobby store and get a dog bone that is 2-3mm longer and see if that fixes it, if not, then I guess I order the vintage brat CVD and axles.

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Stick a tiny piece of foam rubber in the axle cups. That just give you enough back pressure to hold them in but be flexible enough to give as needed. 

Thorp sold these for their dog bone systems (part #4589). 

Terry

 

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