48 replies to this topic

[Revtor]

First scratch built chassis for me, building this in my spare minutes here and there.. hopefully get this done in the next two weeks. Ive got a Parma P138 body to keep it all under.

Im following the basic design of 4 rails per side, thin side pans and center pan floating. 4-1/16 wheelbase, .900 from front axle to guide post. Next step for me is to lay it out in software so I can print patterns for cutting brass and soldering.

One question is how to set everything flat for soldering, does this rely on undersize jig wheels?

Any and all comments welcome, constructive feedback is most welcome!
~Steve

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[Pablo]

To recommend jig wheel sizes, we need to know what ruleset you are building for.

In other words, how much clearance front and rear are you shooting for?

 

Start with the OD of the wheel you plan to use, and divide by two. Subtract the clearance you want, then multiply that by two.

That will be the OD of your jig wheel.

 

Example, .812 wheels/2 = .406 - .050 clearance = .356 X 2 = .712 jig wheel OD

[Revtor]

That makes sense Pablo, thanks.. we want .050 off the bottom of the wheel, but it’s a circle so that much must come off the top too. So .712 jig wheels for .812 tires.

same for fronts I guess. I’ve got buds ball bearing fronts, need .015 minimum clearance. I’ll measure the buds fronts and subtract .030 for the jig wheels..

[Revtor]

Hmm... actually for fronts, the chassis comes ahead of the tires, and that point is where it must be .015.
I guess the easiest way would be to mount the front wheels on the axle and shim the front of the chassis to the height I want, then solder the axle in place. ?

[Pablo]

Your thinking is correct, I do it that way a lot.

It absolutely guarantees you get the exact clearance you want.

 

To make this work, it's critical to make your uprights exactly 90 degrees.

I usually use a 20 or 25 thou spacer.

[Half Fast]

Do you have a chassis jig? It's hard to build without one.

 

Cheers

[slotcarone]

Much easier to build on a chassis jig like everyone else does. As for the side pans they should be at least .050 on an F1 or it will be too light.

[Bill from NH]

Steve, pay careful attention when Mike offers information. He has been involved in slot cars for ages & really knows what he's talking about.  Your chassis sketch looks fine on paper. Precision Slot Car Products in Michigan is one place to get a great chassis jig & jig wheels ( even though theirs are not circular shaped.) Some slot car raceways & mailorder shops also sell these jigs.

[Revtor]

I appreciate any input along my way here, and take it all into consideration!!!!! The fact that i can be in direct communication with you guys who have been doing this for decades is amazing. Elmers in HamRadio lingo. Very appreciative for sure...

No jig! But I have a few tricks up my sleeve to make the lack of jig less of an issue.

Layouts will be completed and pics posted today!

[Eddie Fleming]

I built a lot of great running chassis with a slate block and a machinist square.

 

It is much easier with a jig. 

[Kim Lander]

Eddie...dont forget the old days with the graph paper.

[S.O. Watt]

Pieces of sheet rock with your dwg or graph paper stuck to it works pretty good.

A simple formula for jig wheels is JW= TD-2C (jig wheel= Tire diameter minus twice the clearance)

If you are using a nose piece with struts, slot the axle holes a little to allow some movement to set front ride height after putting some race size tires all around. The longer the front overhang the more you’ll need to raise the plane of the chassis bottom.

Have fun!

[Revtor]

First layout, (minus rails) I need to measure everything and tweak this into reality, then glue to brass and cut parts...
Whats the weight range I should be shooting for on a chassis like this?
Does the two degree guide tongue pretty much sit level on a chassis like this that angles down towards the front wheels?

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[Pablo]

A 2 degree CR tongue sits flat at the rear and angles up at the front.

 

 

 

 

 

[MSwiss]

I'll add to Pablo's post.

It's the ground side down.

The little notches are there to help keep it centered.

On a brass nose piece that is square on the end, (your isn't) if you have them at end, you will be assured clearance to allow your guide to fully rotate.

The theory behind the 2 degrees is that assures the ends of your braid will make contact.

I'll also add that whatever platform you solder the tongue on, should have at least a .060" thickness so you'll be able to get the clearance in front, low enough, for maximum handling.

[Revtor]

Thank you Pablo and Mike. Playing with these parts it looks Ike Ill definitely have clearance and will make sure to solder the tongue ground side down, to keep the back of the braid on the down low.

New layout after measuring everything. 3 rails of .055 sound okay? I could always lay another on top if the chassis was deemed too flexi?

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[MSwiss]

4 of .047" is common, so 3 of .055" should be fine.

In the early days of Retro, Eddy Macdonald use to make chassis for my raceway.

IIRC, they were 3-.055" per side.

[Pablo]

No way would adding another .055 atop three .055 be good in a retro F1.

I built an F1 once that was too stiff - absolutely a terrible handler - very spooky.

 

If you use CR plated wire, it won't rust and you don't have to tin it.

[Revtor]

Slow and steady builds a retro.
Brass cut, makeshift jig next...
Yep the plated wire would be very nice indeed.. and STRAIGHT! These rails are like noodles. . Will take my lumps.. -No problemo.

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[Tex]

a jig makes things easier but know that using one isn't a caveat.... check out the builds of Rick Moore(CMF3 here on Slotblog)..... he uses graph paper.... draws it out nice & neat, then tapes the pieces down to solder them together....

[Bill from NH]

Tex,  Rick also uses a pair of the Champion Align-O-Jig plates with his graph paper drawings. Gene Adams (Gene's World bodies) here in the US & David Lawson in England have both built chassis without any jigs. Gene has a "thingie" chassis build on here built that way. David's was on Slotforum.

[Revtor]

And a jig is born! It should keep the axles square and set the wheelbase and tongue positions. I put pockets for the rear tires so I can get away without using jig wheels. Not as precise, but should get me pretty close, I added a bit of depth to hopefully end up with .050 clearance at the motor bracket face. Well see how my guess (.060 pockets) lands me !
An advantage of laying out in cad is that I can drop a few circles in my drawing and spit out a file to turn into a jig like this. Then machined into a $10 piece of 3/8 high temp phenolic from eBay.
I built this CNC mill 13 years ago, it keeps on keepin on!

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[Revtor]

A bit sloppy with the solder, but the front is together and aligned..

[MSwiss]

Very cool, that you have a CNC mill.

As far as your "bit sloppy" solder joint, it looks like you need more flux and a hotter iron, or even using 2 irons, if you happen to have 2.

That looks like some real thick brass.

[Pablo]

Yup. Those fore-and-aft slots just beg to be pooled with acid and short pieces of solder layed in.

Then lay your hot chisel tip in the slot until everything flows wet.

 

It takes a lot of horsepower to melt solder on thick brass, like Swiss said.

Make sure you have it held down like you show in your photo so it can't migrate.

 

The tricky part is not melting things you don't want to