3D Printed RC Car V3 -- Tarmo3 -- Front Parts [1/3]

by KrisCubed Apr 7, 2019
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Thanks for publishing this for all of us to print and destroy!
I had an unopened spool of Nano Tech Carbon Fiber HTPLA from that now-defunct Maker Geeks company. Hoping that I can print the entire thing from that spool (crosses fingers). Looks like I should be able to if I don't make too many parts for the bin of shame.

Has anyone tried printing this with a larger nozzle yet? I'm cranking out parts at 0.4mm, but I may swap up to a 0.5 or 0.6 if I end up printing a second car. Or maybe if you release a Tarmo4...? :D

Hahaha! I will be releasing a Tarmo4--But don't hold your breath, that will take a few months. Someone on here told me that it took around 650g of PLA to print the car for them, so I suppose you should be able to make the whole car if you have a kilogram of filament.

I don't think it will be advantageous to print the entire car from Carbon fiber filament though, things like gears probably would be better to still use regular PLA since it is so hard it will probably work better--But I don't know for sure, maybe it's worth a test??

I bet you can print the main chassis with a .5 or .6mm nozzle, but parts that require more accuracy will probably need .4mm nozzle or smaller or there will be issues with friction and alignment--But again, worth a try maybe??

let me know if you run into any problems, Good luck on the project!

Hi, my bild its on its way its starts looking something ;P
Thanks allot for tour great work.
I also have to ask you if you can point me one link to buy the Torsion Spring - Torque Damper in Europe. The one i have found doesn't ships to Portugal or have shipping cost like 50 dollars or more. That's the only part i cant find.
Thanks allot

I bought like a 6 pack, and I don't really need 6. Might be cheap enough to send you one of them. Message me if you want to check.

Hmm that hard. I am not sure I can supply a different source to you since I don't know what is and isn't available. Try printing the part first then take it to your local hardware stores and see if they have anything that fits. Other than that try searching the internet for wholesale spring selling websites and see if there is a similar spring for sale. It doesn't need to be exactly the same. If you can't find one that fits, the part can be modified to fit a different spring--I can send you the files so you can mod it.

Impressive design! I'm having difficulty attaching the front shock mount to the front diff case lid. The holes in the lid are too large to thread the screws into and there's no access for a nut. Suggestions?

Could you send me a photo of the problem?--You've probably printed the part in the wrong orientation--Or your print settings are wrong.

It actually assembles as you intended it to. I was expecting the screws to thread into the diff case lid, but you designed it so that the screws thread into the shock mount and clearance holes are provided in the diff case lid. Thanks again for all the effort you put into the design.

Haha yes, I can see how that would be confusing though. Let me know if you have any other issues.

hi, another time its an amazing project,
to complete my car, did you have an idea for a compatible body ?

thanks a lot for your creativity and printable solution for all parts of an rc car.

First, thanks for sharing this great printed rc car

What the name of the rod ? (see attached file)
Can you add it in the BOM ?

thank you

Good eye, I missed that in the BOM. Thats a 3mm threaded rod. Of course it will come in various lengths and you will need to cut it down to around 50-60mm.

Really cool! I normally print and fly planes, but this is very interesting.
Can you say something about the layer hight and width?

Thank you! The layer height that I use is 0.26mm and 0.48mm width using 0.4mm nozzle. 5 perims.

Love what you've done here. My one critique from a design perspective is that you should make an effort to reduce the need for supports. Many of these components could be designed without them. This improves strength, reduces material cost, print time, cleanup time, and improves aesthetics. The front chassis, for example, could easily be flat on the bottom.

You are right, and recently that's what I've been doing, but many of these parts were designed over the last 8 months during the design process, so some parts are from a long time ago, others are only weeks or days old. In fact, I just redesigned the front chassis today before even reading your comment. I made it so that the slant is not needed because I added 1.5mm thickness to the entire length rather than just at the nose.

I haven't posted it yet because I am test fitting and making sure that it all still fits together, but yeah I'll probably post it now.

Definitely most the parts I design now avoid supports and I think that's for the better, as you've stated.

The drivetrain for this looks super cool. However, while looking at the BOM I was bothered by the fact that the differential gear sets and motors cost about the same. It wouldn't cost that much more to have 1 motor on each wheel. Power would go way up, efficiency should go up, and different motors on independent esc's would behave somewhere between open and limited slip diff, depending on the esc's used. It would also open the opportunity to program a drone flight controller to provide torque vectoring and differential steering, as well as traction and stability control. Not necessarily a bonus, but you also skip all of the (admittedly cool) 3d printed gears and most or all of the bearings.

3d printing makes a unique opportunity to build a chassis designed specifically for this. Any interest in modifying the chassis for 4 wheel independent motors?

That price is not an official price, it fluctuates a lot. it was $9 when I got it. you can also check hobbyking and other sites for the same part. There is the option of 3D printing those gears, but they are so small, they tend to strip the teeth.

I've thought about that idea a lot actually, there are a couple of factors, space and cost. For a dual motor, its not so bad, but a quad motor would cost a bit to make and the battery might sag, so a larger battery may also be needed, but I am not sure about that last point.

That doesn't mean that I've given up on the idea, its still on my list of things to test and try to make, but there are other things that are higher on the list. Its sad that amazon manipulates their prices in this way, because any time someone posts a link to a product like that, amazon takes the price up to make more money from the increased traffic. The motor was also MUCH cheaper. Thats why I say on the BOM to search for cheaper options because they are not hard to find.

I did look around a little, and about $15 was the cheapest i saw.

Space and cost, huh? I have ideas for both. I've had a lot of different ideas so far, but right now I'm thinking it'd work fairly well to use Emax clone RS2205 motors mounted in the rims. These motors are super cheap, about $6 each from a good source. And China has enough volume of these that the price isn't going to spike when a couple people order a set.

Putting the motor in the wheel would skip any wheel bearings, of course, as you'd be using the bearings in the motor. The rs2205's have decently large bearings, and should work ok for that. You probably wouldn't have to change too much on the suspension to accommodate the change. Just replace the bearing hubs with motor mount plates I think.

As for battery concerns, quad users are running 4 of these motors all the time without many problems. I don't think that'll be a meaningful issue, but you will want to use a larger battery than you could have otherwise gotten away with.

Anyways, that addresses space, cost, and power, I think. But it also has other concerns. The kv on these motors is quite a bit higher, and I'm not sure if it'll have enough torque to perform decently. But it should have plenty of speed. The other concern is cooling for the motor. The rim would need to be designed to pump air into the motor to cool it. I'm thinking something like Tesla's turbine rim would work well, just with the fins pitched the other direction, as well as being actual fins.

I have one of these motors on my bench, and I can do some torque testing to see if it should be able to handle a car later. If you really are strapped for time, then is there any chance you would be willing to do the CAD work for the in hub motors, and I can put together and test a prototype? I can work out the issues and send you feedback for CAD revisions if needed, and you don't have to worry about building one until the design is proven. What do you think?

Some quick math is suggesting that the 2300kv motors I was thinking about would have an unloaded tire rotation speed of around 200 MPH. That certainly doesn't give me much hope on the torque end of things. I'll see if i can find a motor that would be better suited for the application. I have some ideas already.

Looks really nice! Good work man!

Out of curiosity, what battery and transmitter/receiver are you using? I didn't see them listed anywhere, although I'm sure there are thousands of options

The battery is on the BOM, the transmitter is just a cheap one (linked below), but any transmitter should work as far as I understand--Just as you mentioned.

Cool, thanks for the info! I used to own a Traxxas Sportmaxx, but that was using the old crystal technology, so I knew I'd want to get all new gear when I get this built. You've done an awesome job on this, so far.

Id this a suitable servo? It also comes with a metal servo horn, so it covers two items on the BOM, if so.

Also, Amazon can't find anything from the links for the ESC and the servo

Yes, that will work great, that's the same one I am using. --It's hard to keep links working, I'll try to fix them, but because of work and school my time is very limited.

defiantly want to build this summer looks awesome. are you planning on adding any kind of canopy/ cover for it, or are you going to leave it open?

The plan is to leave it open. Though it can be modified to accept one if you wanted to use one.

This looks amazing! Is it best to print all parts in the orientation that they come up in by default? Or do they need to be rotated/moved?

You are right, they need to be rearranged to the best position for printing. Some parts need support and some don't. Some need raft and some don't--You'll have to use your intuition to figure this out--I plan to make a guide for those who don't know, but I don't know when I will have time to complete it.

Understood, thanks!

Great project!

Looking at the BOM, to understand what I am missing.
Can you please correct ESC link - it is broken

Yes I will fix it, but any brushless motor ESC will work--Of course it needs to be one for RC car or it wont have reverse(Drone ESC's dont have reverse)

Just a heads up- most drone esc's worth having can do reverse. As far as I know, all BL_heli, BL_heli_s, and BL_heli_32 esc's can have reverse enabled with a computer and an appropriate flashing tool. Dshot protocol esc's can use reverse without programming using special Dshot commands, but I can't think of any reason why someone would be using Dshot on an rc car.

However, unless advertised otherwise, it's safe to assume that a drone ESC will need to be reprogrammed for bi directional mode. For most BL_heli based esc's you can do this with an arduino if you know what you are doing.

My quad is set up with a switch on the remote that reverses the direction of all the motors. Helpful if you crash somewhere out of reach and upside down, like a roof. Put it in reverse mode, flip it over, put it in normal mode, and fly away.