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Marui Super Wheelie and Big Bear - a project including CAD

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Marui Super Wheelie and Big Bear - a project including CAD

Old 04-02-2023, 06:09 AM
  #31  
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Originally Posted by 1995 Monster T
The pinion gear and idler gears are going to fail bad. in nylon. Good only for display. The idler gear in stock metal was the weak gear as was the plastic idler gear in the hunter/galaxiy. The zamac stock metal gears will hold up longer than nylon. Sourcing 0..8 pinon gear stock is going to cost more. today. Which is why I stockpiled all the gears for these kits. It's best to just Rember the good old days and display these kits as time has moved on to better products.
Well, I have some friend running sme cars with full printed nylon gears and no visible wear after 5 lipo packs on a 540 silver can... This is a vintage car, and those gears can't be found anymore, and the advantage of nylon is that can be replaced easily when it fails. That being said, I have a Nichimo with a full Nylon SLS printed transmission (except motor pinion) and it is still alive. And Nylon MJF printed gears will be more resistant than Nylon SLS printed gears (NB : this is not FDM : SLS and MJF are printing process where layer adhesion is not an issue in Z axis like it is in FDM).
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Old 04-02-2023, 06:33 AM
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post the link to buy the gears.
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Old 04-04-2023, 03:13 AM
  #33  
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I put it there:
silvertriple by silvertriple - Shapeways Shops
it can be ordered in both PA12 and PA12/GF (glass filled). That being said for those with 3D printer, they know that filled filament tend to be highly abrasive (they deplete brass and aluminium nozzle very quickly) : maybe I should put a warning about this for Glass Filled nylon...
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Old 04-10-2023, 02:32 AM
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Since I started the experimentation with the Flex resin printed tires, I have a big question remaining in my mind... Would it be possible to print a Big Bear tire this way...

I've opened chitubox, put the tire in (not much ways to change the orientation), added supports and looked at it:


It appears my printer's bed is way too small for this... I'll have to try the molding way...
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Old 05-25-2023, 12:07 PM
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I was in a vintage event last week-end (Montluçonnaise 2023). I went there wth 16 cars, and all made at least a few laps of run during the event...



And this included the Big Bear, the Super Wheelie and the Hunter (I still need to mount a video of the runs :-) )...

The Big Bear ran a lap and about 2/3 of a second one, and then stop and did not move anymore (it run around a house at home a bit more).
Upon inspection, the 9T on the idle gear did not survived the run. I will need to find a better solution for this. A test with nylon glass filled was even shorter two weeks ago, so I pulled the gears from shapeways, as unless I can find a solution working for the Big Bear, there is no point proposing this.


It clearly needs to see a dentist :-). I replaced it by another one, and will try again during next event or before (one mentioned that some grease may have impact on the gears)...

For the Super Wheelie, on Saturday, i put it on the track, and it made about 3 meters... What a success! I opened the gearbox on the next day and it was the pinion which required to be tightened correctly, and I was able to run it for quite a good 7 minutes and the transmission is still alive. I will do more tries next event. For the Hunter, it ran quite nicely with a Tamiya Sport Tuned motor. I made a 7 minutes session with it, and again the transmission is still alive at the end. That being said, there was some transmission noice probably due to diff skips. Something I did not have with the Super Wheelie. I've planed to open it for inspection before next event...

Beside this, I've modified my 3 parts printable chassis to ease printability. The best way to print those part is with a quite unconventional orientation, and it happens that elements in the air (on top of supports) are not always perfect. Adding walls to join them to the other side shoul make this easier to print. I did it when I thought it would bring improvements.


- at the rear of the center part : a top bar with the same thickness as bot side of the chassis, and a wall of 1 mm which can be removed afterwards easily.
- on the front part, I bridged the parts

The better orientation I found for the print is on the antenna post for the rear part, angled on the battery pod and rear for the center part and on the rear top upside down for the front.



I've checked holes and nuts dimension : holes need to be drilled to the right diameter (I won't change the tolerance as in case one wants to print it in MJF it is fine while it may be tight for FDM depending on the printer), and nuts are entering in their position when force is applied which means they won't move to much if the chassis needs to be tear down for maintenance, unless you really want to get the nuts out...

Still a few checks to do, but soon this will be published.
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Old 07-08-2023, 01:53 AM
  #36  
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As the Nylon idle gear was not surviving, I got one printed in metal (SLM - powder laser process), and mounted it (no change on the diff side). I ran it quite hard, in various conditions...
Here is a short video extract of one the run https://youtu.be/oaAtrkiP4cA

Big Bear transmission inspection after about 2 and half hours of Lipo 2S (4000mAh) heavy runs (intentionally ran it quite brutally for this as I needed to know about the resitance of my gears - about 4-5 packs passed).




The nylon diff is not showing any signs of wear. it was a mix of different printed parts, but I'm quite sure they would be resistant enough. So this is perfect now.

I have some thinking about the Super Wheelie and will get another idle gear with a small modification printed in SLM, and normally it should be fine... When ordering this I'll get the final diff gear printed set and a metal printed idle gear for the Hunter as well... The Big Bear was clearly the most challenging to tackle, and the nylon idle gear of the Super Wheelie and Hunter are still alive at this stage (but shows clear signs of wear on the Super Wheelie). SLM will come to the rescue...
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Old 07-08-2023, 06:10 AM
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As I have said from the beginning the stock idler gears in nylon won't hold up to a faster more powerful motor. Ok for stock but will explode with a 13 turn modified brushed motor They were meatal in the original for a reason except the buggies.
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Old 07-08-2023, 09:09 AM
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Originally Posted by 1995 Monster T
As I have said from the beginning the stock idler gears in nylon won't hold up to a faster more powerful motor. Ok for stock but will explode with a 13 turn modified brushed motor They were meatal in the original for a reason except the buggies.
Looking at how quick I exploded the nylon idle gear on the Big Bear I'm surprised it is still alive after some good run time with the Super Wheelie. That said, the buggy idle gear doesn't show any sign of wear at this stage, and metal print maybe overkill... And the conclusion is that SLM metal prints work with the caution you may need to work out tolerances as the process is not as predictable than CNC (but still very much less costly than CNC machining).
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Old 07-08-2023, 01:32 PM
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Big tires cause big problems with the big bear. I didn't expect the nylon idler gear would last long. The metal stock gear lasts longer but finding a replacement was almost too impossible now. The super wheelies had smaller wheels and was slightly faster but the nylon gear still won't last as long as metal. The buggies had fine pitch gear mesh not for off road and they wouldn't last long. The demise of Marui was finding parts. especially the gears. The 4 wheel drive shaft cars were better with 32 pitch gears.
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Old 07-09-2023, 04:37 AM
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Following the expérience with the Big Bear idle gear, I redesigned the diff cluster. I also made a different version of all the idle gears designed with SLM metal prints in head.


I've set an order online for a final check. The Super Wheelie Idle gear is printed in 2 versions, so I should be able to assess the needs for the tolerance (the Super Wheelie first SLM version was printed out of specs, requiring a tolerance review), and eventually review the idle gears accordinly for Hunter and Big Bear. I'll be clear on this by end of next week, I suppose.
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Old 07-12-2023, 03:26 AM
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Originally Posted by silvertriple
Following the expérience with the Big Bear idle gear, I redesigned the diff cluster. I also made a different version of all the idle gears designed with SLM metal prints in head.


I've set an order online for a final check. The Super Wheelie Idle gear is printed in 2 versions, so I should be able to assess the needs for the tolerance (the Super Wheelie first SLM version was printed out of specs, requiring a tolerance review), and eventually review the idle gears accordinly for Hunter and Big Bear. I'll be clear on this by end of next week, I suppose.
I wish I had your CAD skills. Great work.
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Old 07-13-2023, 11:55 PM
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Originally Posted by petersen114
I wish I had your CAD skills. Great work.
It is not that complex, there is just a learning curve to absorb for each of the tools you can use for CAD. And that requires time. At the end, it is just a question trying many times hard enough to get it successfull...
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Old 07-17-2023, 10:34 AM
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Got a delivery today...

Diff sets and idle gear for the 3 targeted configuration. This should allow me to check the assumptions about SLM printing tolerances and validate what is needed for Super Wheelies. The Big Bear idle gear is the same dimension as the one working already so this is good. And I'll should be able to assess the Hunter/Galaxy one as well...


I also got a gearbox printed for teh Super Wheelie. I wanted to print one and check my dims for the ball bearings addition before to add this into shapeways...


Later on within the week : test duties :-)
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Old 07-18-2023, 03:41 AM
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SLM idle gears prints are kinda "predictable"
- Big Bear idle gear is spot on, as long as you get the tolerance for the shaft right (+.3mm)
- Hunter/Galaxy is spot on, as long as you get the tolerance right for the shaft and the ball bearings casing (+.3mm)
- Super Wheelie : the big part of the idle gear needed an offset of -.1mm everywhere on the external profile of the bigger gear. Rest of the design is fine (The print with initial design is again 19.4mm for 19.2m diameter expected, while the one with -.1m offset of the external profile is 19.2mm and working smoothly).

So this is it... Diff set remains to test in the different configurations, but at least I have now idle gears for those cars working and reliable...
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Old 07-18-2023, 10:47 AM
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Focus on the Super Wheelie. I put the new diff in. It required a minor shim addition between the locks and big bevel gear on each side but it is now perfect (nb: the previous big bevel gear got printed with some supports, and the left overs were what was maing the diff working :-) ).


I'll have to check out the same for Hunter/Galaxy and for Big Bear before doing the modification on the design (it will be very easy to do). In the meantime, the Super Wheelie works, there is no cracking sound anymore and I don't care opening full throttle... But the motor is probably quite worn, and I'll need to replace it at some point...
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