Super Micro 917k Build, Building a Porsche 917k at less than half HO scale Options

[Flag Slot Racer]

Hello everyone,

I have been lurking on this site for quite some time. I used to be into slot cars back in the 80’s when I was in High School and I am getting back into it now. I have been so inspired by the realistic tracks and super cool cars that are now available. Unfortunately, I have very limited room to set up a track. So somewhere in my warped mind an idea formed… I didn’t have room for even an HO scale raceway, so how about a micro raceway that fits in a small briefcase? If the cars were small enough, I could have an awesome track in a very compact space. People do the same thing with small scale trains, so why not.

I Googled micro slot car and came up with the Japanese micro slot car set. Pretty cool, but the track was boring, the cars were not cars that I was interested in, and it was expensive for what you got. Plus, you really couldn’t buy other cars for the set. Nope. I still wanted to do my own.

So what does this have to do with the scratch build forum? I need to make some micro cars! I really love the 917k, so that’s the car I have decided to start with. I am really new to constructing slot cars, so this plan is ambitious to say the least, but if it wasn’t crazy, it wouldn’t be so much fun.

After some research, I have figured out that the smallest motor readily available motor is a Shicoh 3.2mm pager motor (I have purchased 3 of these, they are tiny). I have taken photos of the 917k and scaled them down until I was happy with the size, with it still being big enough to fit the pager motor. The smallest size I was able to scale the car down to (and be able to fit the pager motor in) was 1/144 or roughly N scale, for those train folks out there. I had thoughts of making it 1/128 scale so it could be half HO, but my desire for a super small vehicle won out over humor.

Below you will see a drawing of the car and where I am in the planning on putting the pager motor. The chassis is a basic design that I have come up with. It does not have any suspension or other fancy features build in, but at less than 1.125” long, I don’t think it will be much of an issue.

http://s1156.photobucket.com/albums/p572/heathnorton/

It is really important to me that the proportions of the vehicle remain to scale, as racing cars looking like dune buggies is not OK with me. I would also like to have as much detail to the body as possible.

So far, the issue I am running into is finding a crown gear small enough to fit in the body shell, with enough teeth to run at least 2:1 gear ratio. I have calculated the gear diameter I need as 3.6mm with a .2 module and a 1mm bore. Needless to say, this is tiny.

Does anyone have any ideas of how to mount the motor to get around this, or have a source for really tiny gears? I have tried didel.com, gizmozone.com (where I got the motor) and numerous other sites.

I am planning to finalize the design of the chassis in CAD and have it printed through ShapeWays, or another 3d printing source.

I am not sure what process I will use to create the body shell at this point. I keep going back and forth between modeling it in 3d and having it printed, sculpting it using clay, or sculpting it using balsa wood. Either way, detail is of the utmost importance in sculpting it as will it be in selecting the material to create the actual shell.

Hope you find this to be an interesting project.

Looking forward to all of your comments and suggestions.

[CJA]

Hi FSR,

fascinating conceptual project.

I can imagine the circuits possible at such a small scale.

Control and driveability remain in question though.

I appreciate the problem with sourcing gears, I once dropped a camera into the sea, which when retrieved gave me an insight into "micro engineering" !!

Believe me, the gears are out there. I do not advocate dismantling your camera for such, but if you find a "duffer", then no holds barred.

Best of luck, and I for one will follow this thread.

vbr Chris A.

[asjwood]

Interesting project! If you can make the cars drive nicely at this scale, then this will be really cool!

[SplitRim]

Yes Very interesting, have you got a body shell in mind or are you going to build it from scratch?

I have some 1/72 scale Series 111 Land Rovers which are a small, cant visualise this

Like Chris, I'll be watching this too

Simon

[Mr.M]

Welcome to the forum!

This sounds like an amazing challenge to take on.

A few years back there was a Micro Machines slot car set produced, but I don't know if the vehicles were self-propelled or hauled around by a spring in the slot or some similar method. I think it was even "based" in a folding case and called "Race-in-a-case!"

Anybody know?

Could be a source of components, or just inspiration.

[DJ]

Ambitious project, this will be a massive (not literally) challenge.
Rather than go for a 917 why not select a model that has already been made in N gauge and convert it?
I used to have an N gauge train layout, the cars were tiny, I can't imagine motorising one.

Best of luck with this project.

[montoya1]

Have a look on ebay for these:



Galoob 1/87th slot cars.

You might be able to scavange these for parts. Good luck.


PS - add your location to your profile. I does not have to be exact, but you never know when that being on display may be of help to you, or somebody else....

[Dave Sykes]

Not sure how useful it is to you but seen some friction and rubber band drives used in ultra small railway stuff.

http://www.nigellawton009.com/Micro_Motor_...ation_Notes.pdf

[montoya1]

That whole site is pretty handy for shaft adapters and small gears:

http://www.nigellawton009.com/PayPal.html

[ThaiRacer]

Could you use friction gears instead of toothed gears?

[Flag Slot Racer]

Thanks so much to everyone for your interest.

CJA - Yes, it remains to be seen how drivable the car will be. I am hoping I can get the car to stay on the track without the use of magnets, but we will see. As far as I can tell, these cars will be way too small to run digital, so my understanding is that the throttle control will not be nearly as smooth? Maybe this could be fixed with the right controller?

Mr. M - Yes, you are correct there was a Micro machines set like this. I found it while searching for cars. That set had you put together the track, and the micro machines cars were far from realistic. My idea is to have the track routed into the case, so as soon as you unfold it you are ready to go. We'll see how that works out

DJ - I looked at the N Scale cars. First off there was nothing that really caught my fancy. I guess model railroad people are setting up race tracks for their trains to go around I'm really into doing this right, so I have set myself a lofty goal. I may come back to just doing an N-scale car that has already been produced if the molding of the body becomes too difficult.

Montoya1- Thanks for the links. I checked out the belt drive, but the problem I have is that my engine will not fit sideways. It's tiny, but not that tiny. I'm not sure how to shift the axis of rotation with belt drive. I'm a little hesitant to buy the micro machine car just for a gear that might work. At $20, it's a bit of a winger. I am waiting to hear back from a couple gear manufacturers in china and elsewhere. Hoping they will have something that works. If that fails, micro machines here I come. Thanks for the tip on adding my location

Thai Racer- I'm willing to use anything that will work. Do you have a source for micro friction gears?

[Flag Slot Racer]

Oh, here is a pic of the motor, so you can get an idea of how small we are talking. Even if I have to add two for torque, I can fit them.

http://i1156.photobucket.com/albums/p572/h.../MicroMotor.jpg

PS: I keep linking to these images in photobucket. I see others put them inline with the text. Is this a slot+ membership thing, or am I doing it wrong?

[Flag Slot Racer]

split rim- Forgot to add... Yes, I will be making the body from scratch. My plan is to either model it in a 3d application and have it printed, or sculpt it in clay or balsa wood for a mold. I am not very experienced at sculpting, so I am leaning toward modeling it in 3d. My concern with sculpting would be to getting both sides the same.

[choc-ice]

A fantastic project! I've done a project with a few similar things - had the chassis made by SLS and the body 3D printed, but at 1:32 scale it was comparatively easy

[Mr.M]

PS: I keep linking to these images in photobucket. I see others put them inline with the text. Is this a slot+ membership thing, or am I doing it wrong?

Anybody can link to images hosted on the net - SF+ just lets you host them here.

When you get the text box up to add a reply click on the "insert image" icon above it and add your photo's URL when prompted.

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