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Judson Superchargers & Judson Rotors
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John Moxon Premium Member
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PostPosted: Wed Jan 30, 2008 7:05 am    Post subject: Judson Superchargers & Judson Rotors Reply with quote

The condition of the internal rotor is the most important factor when buying a used Judson Supercharger. Worn slots in that rotor mean the unit will be noisy and won’t boost to the required rate. If that’s not bad enough worn rotor slots will also cause overheating through excess friction, a vane will eventually snag and the whole kit and caboodle will grind to an expensive halt. That’s when you’ll set out to find a replacement rotor…forget it.

Unless you have access to a NOS rotor to get a competent engineering shop to copy it at high cost to yourself you might as well junk the kit. If there’s still something salvageable you might get one of the well know Judson restorers to resurrect what’s left of it.

That was then…now, this week there’s another solution.

I’m pleased to say Ricardo Deisernia aka “splitpartsunlimited” is now having a high quality Judson Rotor reproduced. You’ll find it in the classifieds: http://www.thesamba.com/vw/classifieds/detail.php?id=561380

I know this sounds and reads like an advert and it’s true I’m bringing your attention to it but I make nothing from this nor do I want anything. I have to say I do want Ricardo to be successful with this repro, it’s not hard to understand why. If Ricardo doesn’t recover his cost and make a little on top, then he and people like him will no longer be in the hobby, taking the risk to remanufacture previously unobtainable parts and we'll all be poorer for that.

If you have a Judson that rattles, you have a worn rotor but now you have a solution. It’s not cheap but it is high quality so go and check it out and consign that “characteristic Judson rattle” to history.

BTW Ricardo is also remanufacturing the impossible to find classic ‘50s/early ‘60s Marvel Oiler Bottle.
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Last edited by John Moxon on Sun Jun 26, 2011 11:43 am; edited 1 time in total
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Snort
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PostPosted: Wed Jan 30, 2008 8:42 am    Post subject: Re: Judson Superchargers & Judson Rotors Reply with quote

John Moxon wrote:


If you have a Judson that rattles, you have a worn rotor


Do you have any information on specifications for wear limits on original rotors?
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John Moxon Premium Member
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PostPosted: Wed Jan 30, 2008 10:14 am    Post subject: Reply with quote

Snort wrote:
John Moxon wrote:


If you have a Judson that rattles, you have a worn rotor


Do you have any information on specifications for wear limits on original rotors?


I know this is not going to sound very helpful but wear on any mechanical part is difficult to quantify. When does the wear become a failure issue?

You can, more often than not identify a Judson Supercharged VW before you lift the decklid. They exhibit anything from a slight tinkle to a rattle like marbles in a tin can, depending on the amount of wear in the rotor slots.

This is a rotor showing typical wear, the red lines depict the ideal profile of an NOS rotor:
Image may have been reduced in size. Click image to view fullscreen.


That rotor will boost to about 2-3 psi will run hotter than normal and will sound like marbles in a tin can, as the vanes slap around in the worn slots.

If you want a Judson to do what it was designed to do make sure it's in the best possible shape. The only way you should be able to tell a VW is running a Judson is from a faint whistle, that's "the characteristic Judson sound."

The characteristic Judson rattle on the other hand is a sign it's on the way out. Crying or Very sad
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PostPosted: Wed Jan 30, 2008 10:41 am    Post subject: Reply with quote

I was lucky; the Judson I rebuilt for Hot VWs Magazine had virtually no wear on the rotor, but still, when I re-assembled it, you could hear a slight "clacking" from inside the blower when it was spinning. I've heard worse, much worse, and as soon as you revved the engine the sound pretty much went away.
I think one of the main things is getting the "end float" or end play, between the rotor and the front and back plates right. As well, when pressing in new bearings, realise that those plates are old, and they are aluminum. Take your time, go slow, and get them in straight.
If you have all the right parts, hey aren't hard to rebuild. They are actually quite a simple affair, and WILL provide extra power, with no decrease in reliability, IMHO.
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DMNCLNR
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PostPosted: Wed Jan 30, 2008 12:28 pm    Post subject: Reply with quote

I feel like i just sat through an infomercial. On a serious note, I will be rebuilding my judson soon, and will buy the new rotor wether it needs it or not, just to be safe. Although they appear to be a bit pricey, I think in the end they will be worth it. I have bought from libreriajenny before, and he is an excellent seller. Hopefully a pricebreak will come soon Cool
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PostPosted: Wed Jan 30, 2008 1:07 pm    Post subject: Reply with quote

DMNCLNR wrote:
I feel like i just sat through an infomercial. On a serious note, I will be rebuilding my judson soon, and will buy the new rotor wether it needs it or not, just to be safe. Although they appear to be a bit pricey, I think in the end they will be worth it. I have bought from libreriajenny before, and he is an excellent seller. Hopefully a pricebreak will come soon Cool


Embarassed Yeah I did say it sounds like a commercial...but there was no way round it. Confused

It's been frustrating having to tell people with dead or dying Judsons there was nothing we could do for them. Laughing

I think Ricardo's rotors will be harder wearing than the originals which were cast from quite a soft material and led to a lot of the wear problems. Back in the day you just ordered another from the factory so it was no big deal.
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PostPosted: Wed Jan 30, 2008 2:32 pm    Post subject: Reply with quote

John Moxon wrote:
DMNCLNR wrote:
I feel like i just sat through an infomercial. On a serious note, I will be rebuilding my judson soon, and will buy the new rotor wether it needs it or not, just to be safe. Although they appear to be a bit pricey, I think in the end they will be worth it. I have bought from libreriajenny before, and he is an excellent seller. Hopefully a pricebreak will come soon Cool


Embarassed Yeah I did say it sounds like a commercial...but there was no way round it. Confused

It's been frustrating having to tell people with dead or dying Judsons there was nothing we could do for them. Laughing

I think Ricardo's rotors will be harder wearing than the originals which were cast from quite a soft material and led to a lot of the wear problems. Back in the day you just ordered another from the factory so it was no big deal.


I think this is a legitimate and very helpful topic!
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splitjunkie
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PostPosted: Wed Jan 30, 2008 2:49 pm    Post subject: Reply with quote

DMNCLNR wrote:
Although they appear to be a bit pricey, I think in the end they will be worth it. I have bought from libreriajenny before, and he is an excellent seller. Hopefully a pricebreak will come soon Cool


Take your rotor to a machine shop and ask them to make a new one for you.

I think you will find that Ricardo's price is quite reasonable.
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PostPosted: Wed Jan 30, 2008 3:41 pm    Post subject: Reply with quote

Awesome, I sold a worn out housing by itself a few years ago for $100 , wish i had kept it, I have had about 5 Judsons and I have to say they were all pretty far gone, finally the spool is available, I had one unit that had huge waves in the cast iron part also, I suppose there was enough left to bore it out but I got rid of that one cheap as well, I just broke another oiler bottle a few weeks ago, I have broken 3 of those darn antique pickle bottles, will have to be more careful with them after seeing the new price! , was there ever a smaller bottle or was that the only size available?
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PostPosted: Wed Jan 30, 2008 6:55 pm    Post subject: Reply with quote

billmetric wrote:
Awesome, I sold a worn out housing by itself a few years ago for $100 , wish i had kept it, I have had about 5 Judsons and I have to say they were all pretty far gone, finally the spool is available, I had one unit that had huge waves in the cast iron part also, I suppose there was enough left to bore it out but I got rid of that one cheap as well, I just broke another oiler bottle a few weeks ago, I have broken 3 of those darn antique pickle bottles, will have to be more careful with them after seeing the new price! , was there ever a smaller bottle or was that the only size available?

I'm guilty of breaking a very nice original one as well!
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PostPosted: Sun Jun 26, 2011 7:05 am    Post subject: Reply with quote

just re-asking the question on what the clearance of the blade to blade slot on a new rotor/blade combo is?

thanks.
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PostPosted: Mon Jun 27, 2011 12:42 am    Post subject: Reply with quote

henry roberts wrote:
just re-asking the question on what the clearance of the blade to blade slot on a new rotor/blade combo is?

thanks.


To quote Alejandro Martin:

Quote:
You can just slide a 0.05mm feeler gauge into the gap between the new vane and the rotor slot. If you place an oiled vane in the rotor, the vane will be held by capillary action but will slide out using two fingers.


EDIT Embarassed Whoops Jerry is completely correct...I misquoted Alejandro's email without thinking so you'll find I have now corrected the measurements.


Picture courtesy of Alejandro Martin:
Image may have been reduced in size. Click image to view fullscreen.

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Last edited by John Moxon on Mon Jun 27, 2011 9:20 am; edited 1 time in total
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PostPosted: Mon Jun 27, 2011 6:25 am    Post subject: Reply with quote

.5mm seems like a lot--maybe .05mm??

John Moxon wrote:
henry roberts wrote:
just re-asking the question on what the clearance of the blade to blade slot on a new rotor/blade combo is?

thanks.


To quote Alejandro Martin:

Quote:
You can just slide a 0.5mm feeler gauge into the gap between the new vane and the rotor slot. If you place an oiled vane in the rotor, the vane will be held by capillary action but will slide out using two fingers.


Picture courtesy of Alejandro Martin:
Image may have been reduced in size. Click image to view fullscreen.
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PostPosted: Mon Jun 27, 2011 6:48 am    Post subject: Reply with quote

avus wrote:
.5mm seems like a lot--maybe .05mm??


1/2 a millimeter (0.0196") is what he said...it has to be a snug fit but it has to slide easily.

EDIT: See above, Jerry is correct...my mistake the measurement is as Jerry suggested 0.05mm.
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Last edited by John Moxon on Mon Jun 27, 2011 9:23 am; edited 1 time in total
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PostPosted: Mon Jun 27, 2011 8:34 am    Post subject: Reply with quote

thanks john. that is a lot more than i was expecting.

edit. it is a smidge less than i was expecting.
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