Bought an oval project a few years ago and it came with a recon. engine ,gearbox and a judson.I thought the judson was brand new as every thing else was new(Pulleys,Oiler etc.)But when running was noisy but pretty much same as others i have heard.Decided to pull it apart and found out it was well, stuffed see photo.

The vanes must have worn away quite a lot, to get that sort of wear on the rotor. Maybe had the wrong [or no] oil, also.

Is that a crack between the slots? If so, the rotor's rooted.....sounds like that place in NZ.

the slots are mean't to be 3/16" wide but are well passed that.It has also been machined oversize so it is time for a new rotor.
The body is badly grooved but should hone up ok.
New rotors are available but are $700 plus postage and vanes $100. So i think first will try to make one.The vanes being oversize ,i should be able to mill these down to the right size.
I have ordered a billet of aluminium 90mm in dia.and 200mm long.
Have honed the body and has come out ok.

Steve

I can not see any cracks in the rotor I have had Judsons since the early 90s in both cars

My rotors are similar in wear and have just add new vanes to make them work

Greg can you see cracks ???

new parts available from the guy in Ney York George F i can look his details up if you want

Looks like you have things under control, Steve. What grade of aluminium are you using? See if you can get a 'radius' in the bottom of the slots, when milling them.

Honestly i wouldnt worry about that one Mine are similar in wear and still work Good
I have purchased a few items from George F in Ney York hes really good and easy to work with for the parts you need

What about remachining the slots and putting in spacers or thicker rotors. ??

tried to press the shaft out of rotor but it would not move.My mates 20 ton press was starting to bend.I think i will make a new shaft as this one has a few battle scars.

Its NOT meant to be removed the steel shaft has tangs on it to stop the alloy section from mooving

its cast as one piece when being made

Please ask questions before you do any more damage

Reckon you are on the right track, Steve. How will you 'key' the al. rotor to the shaft? Please show us your progress...... It will be interesting to see the results.

yes well the hard bit will be keeping the shaft n rotor together

It would be good if you could get a lump of alloy cast onto the old shaft and machine up a new rotor

Interest to know if the OD of the old rotor has varied or still concentric ( so just the slot has worn )

May be easier to mill the slot wider and obtain thicker bakelite material for the new vanes



Ive been fiddling with these since 1984 or so

Dave i am sure you have been fiddling with it since before 1984,
Mitchell

As there is very little load on the rotor,a good shrink fit should be ok.I will freeze new shaft i have made and heat rotor to as hot as i can.Then when shaft and rotor heat up should all hang together.Iam limited by my measuring equipment (have only digital calipers and my old calipers from apprenticeship) Will start for about a .005" interference fit ,which is a lot and
slowly machine shaft until it fits.Will keep you informed

Hi Steve, it was nice to meet you at Warwick, will have to catch up and chat again soon.

Any pics of the new rotor and shaft??
Are you going to cut the new vein slots after pressing the shaft in?
Aaron

Steve

I take it you have seen this http://www.vwjudsonregister.org.uk/ 

Steve, I assume you have in mind some form of 'keying' of the shaft & rotor? Perhaps you could also bore the rotor under-size, to provide an interference fit. Leave the shaft in the freezer for a while, and heat the rotor in the oven [200c?] before pressing together. There are people around[Dangerous?] who could help with precise dimensions, etc.

I have made up the shaft the same specs as the sample,the thread i screw cut (last one i did was about 40 yrs ago) and fits nut like a glove.Next to bore the Rotor i made up two boring bars from 12mm and 16mm s /s i had at hand .I want them to be rigid as possible as it is a long hole.

I tried a test cut in the old rotor to make sure it would work out ok.You can see the amount of wear .Also on the judson registry read about the case history ( i do not know how to do a link, i only learn't how to upload photo's last week).It states that the vane should be a neat fit in the slot,or air will bypass the vane and you lose effeciency .Commonsense pretty much.They will work in this state sort off,and be fine for a drive around the block but i like to know that i can drive from bris. to melb.Also in the resto of the oval the engine was rebuild to new specs. as was gearbox ,the whole car actually (it won 3 trophies at action day) So i want the supercharger to be the same.
Well onto the machining of the rotor first up was to bore a hole slightly undersize of the shaft.

Good luck with your project.

What is going to prevent the rotor from sliding/moving on the shaft when the finished product is in the Judson and actually working on the road? Just the interference fit?
Is it worth pinning the rotor to the shaft, so it cannot move in any direction?