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This is how you true tires...


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#1 Garry S

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Posted 11 January 2017 - 11:45 PM

I wasn't happy with the Hudy and always wanted a Unimat anyway. It's not as portable, but it works better and has a lot more uses!

 

unimat2.jpg

 

unimat1.jpg


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#2 MarkH

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Posted 12 January 2017 - 06:42 AM

When I had access to a surface grinder my tires were ground down to size. Dead flat and turned with a spin fixture. A couple of guys in our club do this same thing as you have set up.


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#3 Bill from NH

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Posted 12 January 2017 - 06:50 AM

Garry,

 

That looks like the model I've had since 1970. At one time, you could find Unimat tooling and accessories in the Sears tool catalog, but that was a few years ago. There is/was a Unimat users group on Yahoo, but I haven't been there in awhile.

 

Because it hasn't been imported in years, you'll probably find Unimat parts selling at high prices. Over the years, I'll repack the headstock bearings, but I've not had maintenance issues with mine.


Bill Fernald
 

How old should a highway be before you tell it, that it has been adopted?


#4 triggerman

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Posted 12 January 2017 - 07:21 AM

I use my MicroMark Mini Lathe with almost the same set-up to rough grind all of my 'recaps.' It saves wear and tear on my Hudy tire truer.

Maybe later today I'll post some photos of my process.


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#5 airhead

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Posted 12 January 2017 - 08:02 AM

How do you use a surface grinder to turn down wheels?
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#6 MSwiss

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Posted 12 January 2017 - 08:20 AM

You motorize something like the below, put your axle in the proper size collet, and while on/spinning, you feed it underneath the spinning grinding wheel.

Speaking of collets, the set-up in the first post would probably be more precise, using a collet to hold the axle, instead of the three (?) jaw chuck.

Also, hanging that much axle out of the chuck, unsupported on the other end, to cut two tires at once, is less than ideal,
with doing two 3/32" tires, of course, more iffy than two 1/8" tires.

5CSpinIndexFixturePinko.jpg


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#7 wbugenis

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Posted 12 January 2017 - 09:56 AM

Speaking of collets, the set-up in the first post would probably be more precise, using a collet to hold the axle, instead of the three (?) jaw chuck.

 
Using a three-jaw chuck will introduce several thousandths runout to whatever you are grinding.
 
My USA-made Hardinge collets are certified to only  0.0007" - good for tires, but not good enough for your commutators.
 
The Hudy, when new, will do better.  The V-blocks on the comm lathe will wear.


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#8 MSwiss

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Posted 12 January 2017 - 09:58 AM

The device below is a better example of what you would use with a surface grinder.

A mere $1,800 plus the prices of 3/32" and 1/8" collets.

nj60-120-100.png


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Mike Swiss
 
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Make checks out to Chicagoland Woodworking, Inc.


#9 wbugenis

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Posted 12 January 2017 - 10:34 AM

A little pricey for tires, but this is what you need to grind your armature stacks.
 
They do get out of round, especially on the open motors.
 
You still have to deal with collet runout.
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#10 Steve Deiters

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Posted 12 January 2017 - 10:42 AM

Interesting set-up. What speed do you run the tires and the grinder? 

I bought an Unimat on eBay expressly for this purpose.

#11 Garry S

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Posted 12 January 2017 - 12:58 PM

I'm running the lathe at its slowest speed and the grinder at its fastest. They still turn into each other (like the Hudy), so it's not ideal but does work fine. The grinder is canted about ½° clockwise to ensure an even cut. The axle extends 1.25" from the chuck, and runout at the far end is less than .001".
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#12 Steve Deiters

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Posted 12 January 2017 - 01:17 PM

Many thanks for the info.



#13 Bill from NH

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Posted 12 January 2017 - 01:24 PM

Unimat sold a special headstock arbor for collets and collets, too. Forty years ago, I didn't have the need to spend the extra money, but I could have used them many times since. Never having done so has always been my biggest Unimat regret.

Bill Fernald
 

How old should a highway be before you tell it, that it has been adopted?


#14 airhead

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Posted 12 January 2017 - 03:49 PM

​ This an old tire machine sold at slot car raceways in the '60s. I was told that Unimat made them.

IMG_2920.JPG

IMG_2921.JPG


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#15 MarkH

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Posted 12 January 2017 - 05:22 PM

The Pinko spin fixture shown above is what I used. I would square and center the fixture to the wheel, 5c collet with 1/8" pin ground down to 3/32".

 

Plenty close enough for slot car tires. The spin fixture also has a slop/stop/locking screw on the top. Just some light pressure and everything ran true.


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#16 hiline2

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Posted 12 January 2017 - 07:34 PM

From the past. Used one like this, it did very well trimming!

tirtetool.JPG
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#17 Garry S

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Posted 12 January 2017 - 09:19 PM

I've seen that ad for the Modelmat hundreds of times, but often wondered if any were actually produced. Now I've seen a real one!
 
This also makes me wonder if I really need the grinder, and might be better off with just a strip of sandpaper like that machine uses. I think I'll give it a try.
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#18 Mach9

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Posted 12 January 2017 - 09:54 PM

I trimmed/sized hundreds of tires (50 cents a pair) at my raceway years ago on a Taig lathe using nothing but  a 1/4" shank boring tool and radiused them after truing with an ignition points file.

I let the lathe go when I sold the raceway, but first thing I did was order another one. A very versatile little machine. Turned hundreds of ink pens on it and numerous other tasks. Have turned comms on it, but just never sprang for the diamond bit.

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#19 Phil Hackett

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Posted 13 January 2017 - 12:36 AM

Then there's this. You're not going to take it to the track: it's 5,500 pounds (2,500 Kilos for our decimal friends....) and won't run on 12v power supply...
 

Click HERE to contact Sonic Products. The messenger feature on my Slotblog account has been disabled.

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#20 Steve Deiters

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Posted 13 January 2017 - 12:38 PM

I always had visions of that X-Acto blade breaking and right into your eye!



#21 Pete L.

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Posted 13 January 2017 - 07:00 PM

Here's my vintage tire cutter by Rual Engineering Co. Inc. out of California (excuse the fuzzy pic)... and yes, it uses a  #11 X-Acto blade as a cutting edge.

 

I always use eye protection when I trim tires!!!

 

CARS DEC 2013 001.jpg


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#22 Bill from NH

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Posted 13 January 2017 - 08:13 PM

Pete,

 

On your tire cutter, how to you set the X-Acto blade to cut different diameter tires? After being cut, do the tires require any sanding other than rounding the tire edges?

 

I've never seen either machine shown in this thread, but I think Rick Thigpen has one of the American Edelstaal units.


Bill Fernald
 

How old should a highway be before you tell it, that it has been adopted?


#23 triggerman

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Posted 16 January 2017 - 07:58 PM

Sorry for the delay in posting pictures of my set up for rough grinding the tires I use for calibrating Knob Jobs on Tire Truers. I usually make a batch of a dozen pairs or more and store them in the freezer until needed. The donuts are Alpha Supernaturals and grind fairly easily.
The Dremel Sanding drum is mounted in a flex shaft which is held in a quick change tool holder. The orange object in the background is an attachment for a shop vacuum.
I'm having issues using my Photobucket account so I posted a quick video on YouTube.

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#24 anumber1

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Posted 25 January 2017 - 03:45 PM

Regarding the setup that started this thread:
 
What do you do about the runout in the moto-tool? My Dremel and B&D moto-tools have lots of slop in the shaft bearings. Wouldn't that runout negate any advantage of the Unimat's nice tight tolerance headstock?
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#25 Phil Hackett

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Posted 25 January 2017 - 06:37 PM

Sloppy bearings would make consistency problematic. I don't see a Dremel in any of the pictures and have no idea how good Proxxons are.

 

It looks like Gary isn't having any trouble.


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#26 Garry S

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Posted 26 January 2017 - 01:27 AM

Runout on the Proxxon isn't a factor.  The axle runs true in the lathe, and even if just the "high spots" of the Proxxon contact the tire it will still be trued properly.  The only time it might cause a problem is if the tire were trued too fast or with too much pressure. 


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#27 Rob Voska

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Posted 26 January 2017 - 07:28 AM

You have to be careful about grinding too fast.  Tire generates heat & expands in the middle then when cool it's low in the middle.  Tires should be rough ground, let sit, then finish ground.

It's easy to see before rounding the edges.



#28 Pete L.

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Posted 05 November 2017 - 09:34 AM

Bill,

 

 I'm terribly sorry for the long delay, I just never got back on this thread 'til now.  The blade is adjusted for tire diameter by loosening the screw that holds the slotted part that is holding the blade. Once the desired diameter is determined, you tighten the screw and it holds the slotted part holding the X-acto blade in place.

Then you slide the entire piece along the two shafts allowing the blade to cut the donut. The cornes do have to be rounded and some sanding of the tread can be done. It's by no means equal to the new machines but it fun !!!


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#29 dc-65x

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Posted 05 November 2017 - 10:45 AM

Just for fun, here's another vintage tire trimmer. I just used it to cut down some vintage 40mm "German" tires:

 

tire trimmer 001.JPG

 

tire trimmer 002.JPG

 

RVM with Germans 003.JPG


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#30 hiline2

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Posted 06 November 2017 - 10:06 PM

OK you guys , Im so envious !  :shok:

 

I used the tire trimmer way back and want to find or build one similar to the ones above. :victory:

 

got some ideas on hobby lathes that may work.  :good:

 

I guess I would rather cut and sand instead of grinding  :dash2:


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#31 elvis44102

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Posted 07 November 2017 - 08:28 PM

i used to help make Limpach fresh cuts.....we has a simple large plain electric motor with a 3/32" axle on it...then Jan had another electric motor with a custom made very fine orange grinding wheel with a large "cut" in the outside diameter of the wheel which exactly matched the whole tire profile rounded ends and all...im sure that wheel wasnt cheap...the whole device was mounted on an old very heavy piece of furniture


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#32 Bazzie

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Posted 08 November 2017 - 02:39 PM

Then there's this. You're not going to take it to the track: it's 5,500 pounds (2,500 Kilos for our decimal friends....) and won't run on 12v power supply...
 
http://youtu.be/nmWTSOyv8Rs


Just come across this. Ooh, giving me some ideas, I've built some cnc machines before...

What I use at the moment is a belt sander and a drill to take my tyres down to around 19mm. Very quick, no heat. After that on my ilpe truer


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#33 Bazzie

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Posted 08 November 2017 - 02:47 PM

Oh, and yes, I also leave the tyres for a day usually after the rough cut to settle properly


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#34 Upfront slot cars

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Posted 08 November 2017 - 03:56 PM

Why not just use an rc car tire machine ? Its basically a mini tire lathe.
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#35 Zippity

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Posted 08 November 2017 - 04:53 PM

So many of you attempting to reinvent the wheel  :laugh2:  :dash2:  :dash2:



#36 Bazzie

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Posted 11 November 2017 - 01:58 PM

Well it's only going to cost me $35, I already have most of the parts


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#37 chaparrAL

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Posted 12 November 2017 - 12:00 AM

What are you guys doing to rough cut the OD and sidewalls in one step?

I will show my first stab at one when I get a chance.


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