15 replies to this topic

[Larry Horner]

When I was scrounging Ebay for parts to restore my Dynamic Bandit, I ended up procuring an almost intact Renegade chassis. So it only seems fitting that I should bring this fellow Outlaw back to life! Naturally one piece that was broken was the notoriously fragile "hook" that locks down the can bearing. But this piece is fairly simple so I 3D modeled it and uploaded it to Shapeways for printing as I don't own a 3D printer plus it needs to be printed in aluminum which most home printers don't support. Anyway, I suspect there are lots of other Thingy enthusiast out there that need this same part so I went ahead and created a shop on Shapeways where they can print there own. Note that this is not a promo as I'm not asking Shapeways for a profit ... this is simply to make the part available for whoever needs one.

 

Here is a link to my shop: https://www.shapeway...s-slot-car-shop

 

Here is pic of the motor hook:

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[Martin]

Nice job Larry, thanks for making these hard to find parts available.

[Rotorranch]

I was building a NOS chassis from some leftover stuff from my Dad's raceway from the '60s in about 1970-71, and broke that part. I have never been able to find another one all this time.

I might be able to finally build that car!

Rotor

[Larry Horner]

Hope you do Jeff ... be sure and post it!

 

Also I have to give a shout out to Martin who was invaluable in this endeavor. Apparently the early brackets didn't have the radiused fillet on the backside of the hook ... mine didn't and that's where it broke. But Martin sent me a picture of his which did so I added it to my model. My guess is that it didn't take long for Dynamic to figure out how fragile this part was hence added the fillet for a bit more strength.

[Larry Horner]

I went ahead and added the bespoked front chassis members used by the Bandit and Renegade. I've printed these in plastic (cheaper for prototyping) and they fit great so while I am still awaiting my aluminum one (for my Renegade), I'm pretty confident in the design so I'll go ahead and make them available too.

[Bill from NH]

I have a question Larry. How do you see the JK Hawk Strap Can on your shop page being used? I ask only because I wouldn't think there was any shortage of FK130 cans. Thanks. 

[Larry Horner]

Good question Bill and the answer requires some explanation. For awhile now, I've been playing around with an AWD design in which a conventional inline motor is driving the front wheels via a forward driveshaft. It's not rocket science but it is a fun project and the cars are a hoot to drive. Problem is that the alignment needs to be absolutely perfect and I've found that the backends of both JK Hawk and Pro-Slot minicans are almost never perfectly perpendicular to the armature. Don't get me wrong, they are fine cans in any conventional usage but just not accurate enough for my needs. Then I saw that John Hallicek was playing around with machining his own strap motors and that gave me the idea to create a 3D printed can which is vastly more accurate than the stamped steel versions. This is still a work in progress but I'll post my project when it gets a bit further along.

 

Also I was not aware when I was publishing my parts for sale that I had published the minican too and I don't want to make this item available until such time as the design is proven so I have since removed it from the shop. So thank you for the heads up!

[Bill from NH]

Thanks for the reply.. You want to do 4WD using one motor with drive gears on both ends, rather than use an auxiliary drive shaft external to the motor. I know nothing about  3D printing, is there some iron formulation you could have the can  made from? The only 4WD slot cars I've driven had two separate motors. An OK friend of mine has built 2, 3, & 4 motor slot cars.  Keep us informed as your 4WD project progresses.

[Larry Horner]

Bill please talk me down off the ledge...

 

I was going to save this for later but I will spill my guts. I've seen absolutely amazing creations from Captain Rick, Jarus and other (the 4 motor car is amazing) in the AWD arena. But I wanted to see if it might be possible to build something that might actually be competitive with respect to modern Cam Am cars. And after pursuing this for over a year now (ok, two), I realized that the major issue is the motor to driveshaft coupler. Specifically with a modern motor spinning 40K+ rpm, any imbalance in the coupler will result in MAJOR chassis vibration. And eliminating this vibration has proved impossible with everything I've tried including very light weight 3D printed plastic couplers.

 

Forward to plan B ... no coupler and this obviously means a motor with a long buttocks (slot blog edits the obvious word choice) armature that extends up to the forward gearbox. So now I think you can understand the need for perfect alignment. I understand your questions regarding an iron based material as the magnetic hysterisis was something I was concerned with as well. But in 3D printing, printing in steel is about 50% bronze (not iron) and worse yet, the results are very questionable in terms of dimensional accuracy ... plus or minus 5% error. Nicht sehr gut.

 

So I asked John H about this and he suggested that the iron content might not be that important in a strap motor as there is no iron extending past the magnets to extend the b field. Furthermore we now have available cobalt magnets rivaling MRUs in b field strength. I know there is lots of conjecture regarding all this but I was really more interested in trying it out to see for myself. So what if I make a motor with an aluminum can (very strong and very dimensionally accurate) with modern magnets to provide ample b field. Will this work, I won't know till I try it? In the mean time, the journey is proving to be a lot of fun.

[Bill from NH]

Larry, no harm at all being an inventor. Many inventions actually work. Sometimes, other useful things are found, created, manufactured other  than what they were looking for in the first place. A Dr. Cooper, who later worked for Eastman Kodak, was working to make clear plastic gun sights &.a plastic for plane canopies in the 40's. Today's outgrow of his research is CA glue. 1/32 cars have used fine ga. wire springs & different types of tubing for motor/driveshaft connectors. Some have used the tubing from a ballpoint pen refill. A Canadian 1/32 racer I know uses plastic pinions to connect his front located motors to a driveshaft that drives the rear tires. This might sound a little crude, but his cars run nice on his Carrera home track. Larry, enjoy your journey as it proceeds.

[MSwiss]

Do I understand this right, and you are going to build a motor that's about 3" long?

Since I've worked on, and finally finished my drag strip, I've learned more and more about drag cars.

Drive shaft cars are sonewhat common, and some are quite fast.

This was an easy to find one, on FB.

That's a pretty reasonable time, for something like that.

I've seen some, that will run under a second.

[Larry Horner]

Bill, I love the story about Dr. Cooper! And very timely too as I had just watched the movie The Current Wars the night before ... highly recommended. Funny how Edison had such a huge blind spot when it came to alternating current.

 

Mike, that's one very cool and apparently fast bus! But in answer to your question, yes a minican with a very long armature is exactly what I'm going to build. I'll post some pictures as it come together. Also not sure if you noticed but I pushed my Bandit and Renegade chassis front members up to my store (the bespoke parts I know you love). Sadly printing them in aluminum is a bit more expensive than I was hoping but then again, there is a vintage Renegade posted on eBay right now for $300 so who knows.

[MSwiss]

Sounds like a fun project.

What would those Bandit and Renegade parts sell for in aluminium?

Do you think they would weaker, stronger, or the same, as vintage Dynamic pieces.

[Larry Horner]

If you follow the link to my shop (https://www.shapeway...s-slot-car-shop), the prices are listed. And just to reiterated, that is the Shapeways cost to print the product (I didn't add markup for myself). You can also activate the 3D viewer to rotate and zoom in on the part. In terms of strength, the printed aluminum is actually quite strong and isn't as brittle as the original die castings. I've also printed them (the Renegade front) in nylon impregnated plastic which might actually be strong enough (and is cheaper) but figured if you're restoring a vintage outlaw, you'd probably want to make it as close as possible to the original.

[MSwiss]

Now I understand.

As I read it, they were only available in plastic, because of affordability.

What you meant was you originally did it in plastic, to more economically check the part out for fit.

I didn't read it carefully enough.

It's awesome what you are doing.

Back to the motor, how long do you think the armature will be?

It's been 15+ years since I've been on a dynamic balancer, so I'm trying to visualize if they would accommodate something that sounds like it would be 2"+, in length.

[Larry Horner]

I'm house sitting for friends right now so I can't give you an actual measurement but my prototypes all have a common 4" wheelbase and I'm using conventional motor carriers front and aft (specifically RGEO). So if you image a standard Can-Am chassis with the motor in the usual position, the front of the armature would extend forward maybe 2.5". I too am worried I might not be able to dynamically the arm but I'm also sure even a static balance would be much better than my efforts so far with couplers. I'll be home tomorrow and will post a picture of one.