BloodClod's Belt-Drive Yokomo 834B

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Mr. ED
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Re: BloodClod's Yokomo 834B

Post by Mr. ED »

BloodClod wrote: Wed Jul 19, 2017 5:30 am
2 months? Wow... why is it taking so long?

You might consider buying a printer and doing it yourself. I've been interested to pick up 3D printing for quite some time now but the start up cost was just too high - but I did some research recently and it seems the tech has reached a point where you can get a decent machine for quite a low price provided you're willing to do some assembly and set up.
...
Any pics of your pulley design? :)
I went with some guys from the netherlands who ate experienced with 3d printing for rc cars and got good advise and feedback on my designs from them. They warned me beforehand it would take time, but it's gotten beyond what I expected by now.
I'm not sure the home printers can deliver what I want. Even the more advanced printer I got a prototype from delivers a rough textured surface which didn't convince me to do gearbox components.
So, I didn't design a pulley. I made suspension arms for the works'91. I've also got parts designed for the ultima. But I want to test those arms before ordering more prints.

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Re: BloodClod's Yokomo 834B

Post by BloodClod »

Mr. ED wrote: Thu Jul 20, 2017 11:22 am
BloodClod wrote: Wed Jul 19, 2017 5:30 am
2 months? Wow... why is it taking so long?

You might consider buying a printer and doing it yourself. I've been interested to pick up 3D printing for quite some time now but the start up cost was just too high - but I did some research recently and it seems the tech has reached a point where you can get a decent machine for quite a low price provided you're willing to do some assembly and set up.
...
Any pics of your pulley design? :)
I went with some guys from the netherlands who ate experienced with 3d printing for rc cars and got good advise and feedback on my designs from them. They warned me beforehand it would take time, but it's gotten beyond what I expected by now.
I'm not sure the home printers can deliver what I want. Even the more advanced printer I got a prototype from delivers a rough textured surface which didn't convince me to do gearbox components.
So, I didn't design a pulley. I made suspension arms for the works'91. I've also got parts designed for the ultima. But I want to test those arms before ordering more prints.
All the 3D prints I've seen from home printers have some degree of the "lines" created by the individual layers... although I must admit that some of the work I've seen has really been able to minimize this. I'm not sure if the tech at this point is able to produce the same kind of finish that moulded parts have without sacrificing precision. The parts I've ordered from Shapeways doesn't have the "line" textures but they have a very fine "sand" like finish to them.

As such I think it's going to be hard to match the smoothness and precision of moulded transmission parts. I only did this because I this it matters less for pulleys than for gears.

My hope is simply to be able to service a vintage runner without worrying about destroying a part and sidelining the car for good. :)

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Re: BloodClod's Yokomo 834B

Post by GoMachV »

The powder you see in Shapeways parts is the material before it is sintered. As I understand it, instead of a solid rod being liquified and "printed", they have a laser that fuses the powder.
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Re: BloodClod's Yokomo 834B

Post by Mr. ED »

You're both correct. But even those prints will have lines, more or less pronounced depending on the shape and orientation of the surface relative to the coordinate planes. A flat plane in a slight angle will have steps. A spherical surface has rings. It gets better with higher resolutions, but particle or filament size limit the possibilities there.

The prototype I received came from a similar printer as shapeways uses. Let me check if you can see the steps on the pics I posted in another thread.
PS: http://www.rc10talk.com/viewtopic.php?f=29&t=41329&start=105
You can see the texture but not the steps in these pictures. I'll take another pic when I'm back from holiday. The main surfaces suffering are the front and back of the rear arms: angling just a couple degrees forward.

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Re: BloodClod's Yokomo 834B

Post by BloodClod »

Some progress over the last couple of days...

First I printed up a new set of pulleys and a new belt tensioner with some revised dimensions and they came out looking pretty good.

Image


The main difference in this version of the pulleys is that I was playing with the idea that since the front pulley was closer to the centerline than the rear pulley (making the belt "bend" around the center tensioner), it might be possible to move the rear pulley even further away from the centerline so that the front pulley, belt tensioner and rear pulley are all aligned but slightly canted.

But after installation my theory didn't pan out in reality... due to the way the belts wrapped around the pulleys they just didn't run well in such a configuration.

So it was on to version 3 of the pulleys. This time the idea was to offset the front another millimeter outwards and the rear pulley closer inline to try to line everything up. I also designed a guide pulley in the center to ensure the belt stays where it's supposed to be as it routes around the tensioner. Everything fit great and things were looking good.

Image

A quick test on the road and everything worked great! The car ran smooth and the belt never skipped a beat. It'll have to hit the track for a more thorough testing but I'm so glad so far the conversion was working better than I had ever expected. lol!

The car was looking very different from what I had started with. Here's how she stands now. :)

Image


Earlier in the day, while I was driving I had an idea for a design for an easy way to mount 2.2" JCRACING wheels on my 834B while getting the right width I wanted... I booted up the CAD software and shortly after a pair of these were done! Introducing my version of the Yokomo vintage wheel widener!

Image

I had previously used carbon plates cut to the shape of the "square" to widen the wheel and they had worked fine but there were some limitations - namely I was limited to the width of the carbon plates and secondly when they extended past a few millimeters the wheel was no longer engaged to the original metal hub so the only thing driving the wheels would be the 2 screws holding the assembly together. I doubt that was an issue, but this design actually keys over the drive hub and into the wheel to better transfer the power.

Had a big smile when everything fit snugly together with no slop and when I powered it up everything ran true.

Now I can easily adjust my width by printing them up according to what I want to achieve. Getting the car to fit easily available 2.2" wheels nicely has always been something I could not easily fix but if this holds up then I would've solved another concern that stood in the way of regular running of this car.

Here's the width of the car with JCRACING wheels I bought a long long time ago.

Image

As I type the second pair is printing on the printer for me to mount onto my front wheels.

More pics and mods to follow!

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Re: BloodClod's Belt-Drive Yokomo 834B

Post by BloodClod »

Just a quick update to show you how the car looks now with the widened stance and modern 2.2" tires.

Aside from that, I did something else quite significant... can you spot what it is from the picture? :)

Image

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Re: BloodClod's Yokomo 834B

Post by tiger1 »

BloodClod wrote: Thu Jul 20, 2017 6:57 am
a01butal wrote: Thu Jul 20, 2017 4:42 am I posted this a while ago. FYI

http://www.rc10talk.com/viewtopic.php?f=29&t=36513
Hey a01butal, thanks for the link. Your thread was one of the many that I referenced when working out how I wanted to do the belt conversion. The set you have certainly is interesting to me, mainly because it still uses the stock chain guide. I think it works because of the large pitch of the teeth on the belt. I was curious how it your setup would perform but I think you mentioned it was only going to be a shelf queen.

Yours is the only commercial conversion set I've seen - what a rare find!
Bro, you really are doing a great job here. A GREAT GREAT car!!

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Re: BloodClod's Belt-Drive Yokomo 834B

Post by rraeford »

You made new rear arms.

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Re: BloodClod's Yokomo 834B

Post by BloodClod »

tiger1 wrote: Tue Jul 25, 2017 8:16 pm Bro, you really are doing a great job here. A GREAT GREAT car!!
Thanks!

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Re: BloodClod's Belt-Drive Yokomo 834B

Post by BloodClod »

rraeford wrote: Tue Jul 25, 2017 9:21 pm You made new rear arms.
Yes! Since I had widened the car I thought I could attempt lengthening the car as well and I decided to try to make some new arms and lengthen them to achieve a longer wheelbase.

This 834B I'm working on is also one of the earlier versions so the original arms are quite flexible - these new ones are also designed to be stiffer with a slightly thicker profile (for better fitment into the pivot blocks) as well as with the additional support running down the center of the arm.

It took a little adjustment but the bearings seat snugly and now the car has a wheelbase similar to the Kyosho Optima... not quite modern day standards but the additional length should help the car handle today's tracks a bit better.

Image


On the front end there are also some updates to try to improve the steering. First, under the top deck you can see a new spacer which is there to let the top deck run parallel to the chassis. With the original top deck gone, the steering seemed really sloppy because the two long screws were holding the bellcranks would flex when the servo was turning the wheels. I made a simple brace to connect both the screws together on top and then to the chassis so the servo motion is better translated through the bellcranks to the wheels.

Image

With the added width and these adjustments, the car is steering a lot better than stock. Though I might want to work on some stronger bellcranks as the stock ones are a bit flexible.

I think I'm almost done with the car. Initial testing seems really positive and I'm looking forward to a test on the local offroad track. :)

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Re: BloodClod's Belt-Drive Yokomo 834B

Post by Mr. ED »

The right equipment in the right hands!
keep us posted, I love this stuff

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Re: BloodClod's Belt-Drive Yokomo 834B

Post by Dadio »

seriously though that's excellent work well done.
If a jobs not worth doing then its certainly not worth doing well.
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