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Step-by-step Stock Car chassis build


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#1 JimF

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Posted 07 October 2016 - 12:36 AM

In recent past, I’ve done a lot of tech overviews talking about chassis designs and performance and stuff. What I haven’t done for a while is a step by step on anything. This article features a fairly simple 4 ½” Stock Car built from the latest evo of R-Geo Ricks new chassis plate. The design is pretty simple so what I’ll be doing here is focusing on some details that some newer builders may find useful.

 

Kits are a wonderful way for the novice builder to get his/her feet wet but they can also make really good race cars for the more serious builder. The difference between the two types of builder may be that the more experienced know that you don’t just open the bag and basically shake out a finished product onto the table.

 

So….for this build, here’s what we are starting with…..Ricks newest iteration of the Stock Car plate.

  • Plate is .040 thick.
  • Dragonslayer type pan hangers are .032.
  • Guide tongue is .042 hard steel.
  • Bracket is .050 Z-poid (angled face)

DSC02609.JPG

 

Plate with some dimensions and the pan cuts marked.

  • Inner edge to edge of the rail slots = 1.00” to match the bracket width.
  • Inside edge of rail slots are positioned perfectly but slots not cut for any particular rail setup.
  • We’ll be using 2 rails/side of .062 in the slots so they’ll get widened to about .128”

DSC02610.JPG

 

That thing I harp about all the time……square up the bracket.

  • Use a good file and push/pull the bracket face down the file with pressure.
  • Then follow on each “leg” of the bracket.
  • This’ll get the bracket face and legs flat.
  • Now, screw in a beater motor and square up the legs to the motor/bracket face.

DSC02611.JPG

DSC02614.JPG

 

Now….get the rear bearings and jig wheels in place and get ‘er on a really flat block.

  • Check that the bracket legs are flat on the block surface.
  • Jig wheels are both sitting flat.
  • Axle is parallel to bracket face.

DSC02616.JPG

 

Into the jig and center the motor-bracket assembly.

  • Jig wheels hold the axle in place outboard.
  • Retainers from old spur gears inboard center the motor-bracket assembly.
  • Square it again with the mini-square. (Zona or Exacto or Excel are all the same piece)
  • You can see positioning pins in place here at 1.00" matching bracket and rail slots.

DSC02618.JPG

 

Lay out the components and rails in jig for trial fit.

  • Jig has positioning pins in place at 1.00” outside-outside all the way down the jig.
  • You can see some marks on the rear pan hangers where they’ll need trimmed.
  • 2 rails of .062 piano wire/side are laid in place to check fit in the widened rail slots.
  • Near side front slot needs a few more more file strokes for an easy fit of the rails.
  • The rails rest flush to the bracket, flush against the positioning pins and slip into the rail slots.
  • Rails must hit all these marks and slip into the slots easily with no “spring” to them.

DSC02619-001.JPG

 

Ready to turn on the soldering iron…..YAY!!!!

  • Front axle upright slots are oversized so a JK 3/32” solder on retainer is used as a bushing.
  • These will be soldered to the uprights but not to the axle. Axle will now be centered in slots.
  • Axle not soldered in at this point so the axle can come in and out.
  • Main chassis rails are aligned at bracket, pins and front and checked for fit.

DSC02622.JPG

 

Check for square one more time and then tack solder main rails at bracket and front slots.

 

DSC02623.JPG

 

OK....that's enough for tonight. I'll finish this up tomorrow.


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Jim Fowler




#2 JimF

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Posted 07 October 2016 - 12:55 PM

OK……part two.....here's the rest. Advanced builders are gonna know all these little steps but a novice might not. Anything outlined here would apply to most any kit build regardless of type.

 

Trial fitting the pans and pan hangers.

  • Here, the rails are tacked front and rear on all four corners.
  • Pans have been cut free from the nose earlier and now dropped in place.
  • Note the 1/16” square brass rod spacer to narrow the pans up to 3.0” width.
  • Pan hanger dropped in place to see where it’ll need trimmed.

DSC02624.JPG

 

More fitting of pans and hangers

  • Pan hanger has been trimmed some and is almost right.
  • There is some red indicator on the tail of the pans showing an area I want to trim some.
  • This will give a little more spacing so that the tail of the pan can’t ride up on thanger and get stuck in the case of a hard hit.

DSC02625.JPG

 

 

Finishing the trimming and placing stop tubes:

  • I’ve got the pan hanger and the spacing around it about where I want it.
  • Stop tubes of 3/32” box tubing are in place on the pan hanger and also out front on the ears of the nosepiece. These will accept the pan “hinge” rods.

DSC02626.JPG

 

 

Soldering hangers in place and starting to flow solder the main rain rails.

 

 

DSC02627.JPG

 

 

Third main rail going in.

  • I decided to run 3 rails/side instead of two so they’ll go inboard of the two mains.
  • This bracket comes with a little slot pre cut in the bracket face for an inboard frame rail but it’s made for smaller wire.
  • The additional rail has a sharp angle cut of about 45* on the rear tip. Now, it will slide into the slot on the bracket face.

DSC02628.JPG

 

Third rail in place and all rails flow soldered full length.

  • Third rail nests under the bracket face at rear.
  • It butts against the nose plate.
  • All rails are full soldered at this point.
  • Rear bracing is two bits of .047 across the rear main rails which are then trimmed off flush with the bracing wire.

DSC02629.JPG

 

Next up we hang the pans in a shaker style configuration:

  • The following are some steps that novice builders may want to follow closely.
  • The front hinge rod is placed on a standoff so that the pan and the tube are at the same height.
  • Rear hinge rod could also go on a standoff but I chose to put a dogleg bend in it instead.

DSC02630.JPG

 

Front Detail:

  • Ear of nosepiece is .040, tube wall is .015 so bottom inside edge of the tube is at .055.
  • Pan is .040 so a standoff of .015 brass strip raises the hinge rod to the exact right height.
  • Hinge rod of .047 is in place and flat on the bottom of the tube.
  • Front spreader bar of .047 is in place here as well.

DSC02632.JPG

 

Rear hinge rod detail:

  • The pan hanger is .032 and the tube wall is .015 so we have a thickness of .047 to match.
  • Pan is .040 of course so I need a .007 standoff height for the hinge rod to lie flat.
  • I had some .010 brass but that’ll raise the hinge rod a bit too much.
  • If the rod is not flat on the bottom of the tube, then the pan will hang below the chassis a little.
  • I didn’t have any .005 brass which would have probably worked OK
  • So….I bent a slight dogleg into the hinge rod. This is just visible in the pic.
  • Rear spreader bar is in place here as well. It is .055 sitting on a .025 standoff.

DSC02631.JPG

 

Next is the guide tongue.

  • Axle slides out of the way so I can get at this step easily
  • The guide tongue has two lines drawn on it. The rear one shows the cut off line.
  • The front line shows where it will get a slight upward bend for the guide angle.
  • I used a bending brake for this b/c I have one but it can be done with pliers/vise etc.
  • Also there will be a .032” standoff on the bottom side of the guide so a full thickness guide can be used.

DSC02633.JPG

 

Front axle detail:

  • The guide tongue is cut off, bent, and in place on its .032 standoff.
  • Front axle is slid through the JK retainers for soldering in place.
  • There is a little too much space around the retainers so I don’t think I’d get a good joint in the axle slot.
  • A very small (#4) brass washer fits over the axle and just fits over any bit of the retainer that protrudes from the upright.
  • When soldered in place, I’ll have a nice solid connection.

 

DSC02634.JPG

 

Front axle in place and washer fully soldered.

 

DSC02635.JPG

 

Final steps to the finished product:

  • On the front, there is a bit of .062 wire reinforcing the very front frame ears.
  • At the rear, there is a bit of .055 wire acting as a gusset between the bracket and main rails.
  • This will go in the tumbler, then the pin tubes will go in but this baby is DONE!!!

DSC02636.JPG

 

I realize that these steps are super basic for a lot of builders. However, when somebody new to this buys a kit, they miss some of these steps. Often times, their bracket is not square or their pans hang too low, move too much, or bind. I think that is one of the main differences between the novice and the expert kit assembler that gets great results from kit builds.


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Jim Fowler

#3 Tim Neja

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Posted 07 October 2016 - 01:56 PM

Great explanations and technique Jim!! I've built a lot of frames--but I always learn something from you!! Thanks  Tim


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#4 Dominator

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Posted 07 October 2016 - 06:24 PM

Great job as always Jim. Very straight forward buI'll and will be great for a first time builder.

A motor is only as fast as the chassis it's in.
 
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#5 Joexemm

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Posted 08 October 2016 - 07:17 AM

=O I gotta do this one! HAHAHA! I love this your craftsmanship blows my mind. I hope one day to be that neat.

I have to ask how do you hold the little tiny bits in place when your cutting them and soldering them? I am losing all my finger prints and nerve endings. =.=
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#6 slotcarone

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Posted 08 October 2016 - 08:28 AM

Joe,

To answer your question about holding pieces in place I use an old small flat blade screwdriver that I cut a notch in. Also have an old plastic handle allen wrench that I soldered a curved piece of .032" wire on to hold the pin tubes in place.

Also those are really beautiful builds Jim does but I would guess there has been some clean up work done before the pictures were taken. Maybe Jim will chime in. I have my own method that I have shared and maybe Jim will share his.

Mike Katz

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#7 JimF

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Posted 08 October 2016 - 11:17 AM

I also use small screwdrivers with a notch cut in the tip. I got that idea maybe from Mike Swiss (I think). These are great for holding small bits like tubes and wires. I also semi-regularly use small pinch clamps from X-Acto that work like tweezers in reverse. I'm about to leave for a couple days and don't have time to look those up but I think they are still made. I don't use them a lot but they are really useful little guys to have on the bench.
 
I've mentioned this before but as Mike says, I do for sure clean things up before taking pictures. With flux goop all over the place, it's often tough to see what the heck I'm talking about. I also try to use minimal amounts of solder and take my time. Even so, the solder joints get cleaned up as well. An example are pics #1-2 in part two which have not been cleaned vs pics #3-4 which have. I use various types of brass and steel brushes for this and then finish with flexible rotary brushes in various grits and styles. I also made little buffing wheels from Scotchbrite for the rotary tool.
 
I generally don't do as much cleaning as this until the end but on article cars, I do a lot more so stuff is visible. On stuff for myself or for testing, I'll only clean once or twice or any time that I need to look at a joint closely to check it or when I'm going to put the work down for a few hours or until the next day.
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#8 Jairus

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Posted 08 October 2016 - 05:36 PM

I tend to use an old eXacto blade with a notch cut into it.  Plenty of those around right?

Nice article Jim, be a great article in a magazine.

 


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#9 gc4895

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Posted 22 October 2016 - 03:43 PM

Just wondering what caused the addition of the 3rd .063 rail.  Obviously, greater stiffness was deemed desirable. In retrospect, would a single .078 rail been a better (or alternative) choice?  Were you happy with the weight as completed?

 

I'm wondering what the guide lead chosen was for this chassis build?  Some regulate the length at 0.75 but I'm thinking 0.9 might be a better choice if operating in a non-guide length regulated environment. 

 

If you have tested this chassis, any thoughts on things one might consider doing differently? 

 

Thanks!


Mark Bauer

#10 Slot Car Mods Magazine

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Posted 22 October 2016 - 05:06 PM

Fantastic work, and very informative...

 

Thanks for sharing...

 

All the best...

 

Ron...

 

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#11 JimF

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Posted 22 October 2016 - 10:27 PM

Just wondering what caused the addition of the 3rd .063 rail.  Obviously, greater stiffness was deemed desirable. In retrospect, would a single .078 rail been a better (or alternative) choice?  Were you happy with the weight as completed?

 

I'm wondering what the guide lead chosen was for this chassis build?  Some regulate the length at 0.75 but I'm thinking 0.9 might be a better choice if operating in a non-guide length regulated environment. 

 

If you have tested this chassis, any thoughts on things one might consider doing differently? 

 

Thanks!

 

My own frame like this is 3 rails (2 brass. 1/wire) and it's very good. I thought that perhaps 2/wire would be about the same but when I got into it, I realized that I'd better stiffen it some. Yes, a single .078 would be a good alternative and in fact, I do many of my stock car builds that way. I just don't build 'em all the same. This would finish at about 125-130 depending on body. Additional weight is often desirable.

 

The guide lead on this one is about .850 and since we don't spec. guide lead, I often vary it between .800 and possibly .925 on the longer side. As far as what to do differently, scratchbuilding is pretty open ended. I very much like the pan movements on this one but the frame rail setup could be about anything. 1X.078 is very good and sorta basic but 3X .062 is good too. Haven't tried 7X .047 but it could be good as well.

 

This one happens to be a customer car so I haven't run it but it's awfully close to my own which is excellent. I have found that there usually doesn't seem to be any magic bullet in chassis design and a lot of different things work. Naturally, that doesn't keep me from searching for that magic one cuz it is a hobby after all.

 

Heck......you oughta see my current F-1 projects.....some real searchin' goin' on with those........ :crazy:


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