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Post by JonW on Dec 9, 2015 1:16:07 GMT 1
Ok, fist up no these are not for an RD, they are for KTM forks for my XT500.
Im looking for these sizes as listed in the parts manual:
DU-bus d50xd54x20 P10
DU-bus d50.7x20
Does anyone have a supplier for parts like this, locally ive come up empty :/
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Post by steven on Dec 9, 2015 2:26:48 GMT 1
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Post by JonW on Dec 9, 2015 12:26:56 GMT 1
Thanks Steven... Ok.... I found this one: shop.eriks.nl/en/bearings-sliding-bushes/ptfe-flanged-bushing-maintenance-free-steel-backing-bb-50-20-du-12440531/seems its a 50 x 20... so not perfect.... and dont list anything 50.7... which i can only assume is 2inch? but thats 50.8, not .7.... anyone else have any ideas? To be honest im not really sure what the sizes mean. 50.7 x 20 seems like its 20mm tall and has an OD of 5.07 and the DU coating is on the 50.7 outside i guess? The other one is more complicated, im wondering if its DU coating is on bot inside and out and the OD is 54 and the ID is 50,, and its also 20mm tall... P10, tho... wossat? Of course I can pull the forks apart but without any new ones to go in, im feeling like its a futile exercise as Ive no idea where Id find the right sizes  |
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Post by steven on Dec 9, 2015 20:46:27 GMT 1
Hi Jon, DU bushes were developed and patented by The Glacier Metal Company Ltd in the 40,s and 50,s. The Glacier Metal Company was founded in London in 1899. During the Second World War, some Nazis were trying to bomb the Glacier Metal Company in London as it was a bearing factory, so the factory was moved North to Scotland, in an attempt to keep it out of reach of said Nazis. The same factory, where DU bushes were developed and made is still in Scotland today and I work in it within the Maintenance Department. We no longer make DU bushes in Scotland, as they were "asset stripped" a few years ago, but there was a time I could have told you the name of the guy that worked the machine that made DU bushes ! The factory is now owned by Mahle Engine Systems, a German company, which is who I work for. Today DU is the most successful of composite bearing materials, combining the excellent dry bearing properties of PTFE with the mechanical properties of conventional metallic bearings, and has a wider range of performance and greater number of applications than probably any other bearing material......(these three lines I copied from the DU/DU-B designers hand book) A while back I decided I wanted to replace the fork bushes in my LC. After a bit of digging about I discovered that fork bushes are not available for LC,s and never have been. If you wanted to replace the fork bushes in your LC, you had to buy the complete lower fork leg, which had the DU type bush fitted in it. As we all know, LC forks are 32 mm O/D. The nearest size bush available was a 32 20 DU, which denotes a DU bush with a 32 mm I/D and 20 mm long. The bushes that are in LC forks are 32 mm I/D and 15 mm long, so I made up a little tool to hold the 32 20 DU bush so I could cut 5 mm off them in a turning lathe to effectively make them 32 15 DU. 32 15 DU bushes are not available off the shelf, so that is why I had to cut down 32 20 DU ones. I have had these bushes in my fork legs for years and all is well. I know you are looking for DU bushes for your XT 500 and none of this will be relevant to your particular bike, but perhaps you might have to do what I did, and find a bush that you can adapt as I did, to fit your particular application. Here is a link to a post from last year on here, when someone else was asking about fork bushes. A few weeks ago it was announced that half the factory is closing at the end of February and half the work force will be made redundant. Some of the work is being taken to a country where the labour force costs are cheaper. I found out only today that my job is safe, but half my colleagues will be getting payed off in the new year. Sad times indeed. Sorry for the long winded post, I hope it is of some use. Regards, steven. rdlccrazy.proboards.com/thread/25572/lc-fork-leg-busheswww.gracesguide.co.uk/Glacier_Metal_Coen.wikipedia.org/wiki/MAHLE_Powertrainwww.mahle.com/mahle/en/products-and-services/motorsports-and-special-engines/index-2.jsp    |
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gsexr
Thrash Merchant
Posts: 352
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Post by gsexr on Dec 9, 2015 20:54:16 GMT 1
I luv genuine engineering to solve a problem.
Well done that man
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Post by JonW on Dec 10, 2015 3:02:30 GMT 1
Thanks for the info Steven, I remember your LC DU bush post, its a classic and I have it bookmarked.
Naturally, I am happy to do a bit of slicing down in a lathe of course, thats not really a problem, Im actually floundering at the first hurdle, can you help with deciphering what the sizes actually mean and why there are 'd's in there as well?
In the meantime Ive emailed Mahle in case they can source them, if you have any more links then im all eyes...
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Post by steven on Dec 10, 2015 8:15:48 GMT 1
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Post by JonW on Dec 10, 2015 8:49:22 GMT 1
Er, Im more confused than ever... These are the sizes arent they?
DU-bus d50xd54x20 P10
DU-bus d50.7x20
Cheers for your help with this mate.
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Post by Tobyjugs on Dec 10, 2015 17:07:56 GMT 1
Hi jonw if you decide to get anything from Eriks get in touch i usually get 50% discount. They are very expensive to begin with so in reality it's just a little cheaper than somewhere else.
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Post by steven on Dec 10, 2015 21:06:17 GMT 1
...Hi Jon, I have looked through the Glacier DU book, and can find nothing in the product range under those numbers. The Glacier DU book says "non standard components are not available." ...so you must have DU bushes....NOT made by Glacier. So we can put the Glacier DU book in the bin ! www.ktm-parts.com/BC25714134.html = 50 54 20 DU bush........... Your first bush is in the above link, so it is available, so someone makes them, so they should be easily sourced. I couldn't find anything on your 50.7 x 20 bush, until I copied and pasted this, DU-bus d50.7x20 into google...then I got this... advrider.com/index.php?threads/wp5060-bushes.1110583/ ...which informs me that the bushes we are looking for are from a KTM 250 EXC and seem to be quite rare ! It looks like no one makes a 50.7 x 20 DU bush,....so were they made by some company specifically in that size for KTM ? are they specials? whats special about them? I see someone is suggesting Marzocchi 50 mm bushings, I think if you bored out a 50 mm DU bush to 50.7 mm you would take most of the DU out of it and be left with just a steel bush ? Do you think making them out of oilite might be an option or not ? en.wikipedia.org/wiki/Oilite .....but I read this bit .... " Honing and grinding should not be performed on any surface that is in contact with the journal as these processes always smear the pores." If there are two bushes in each leg.....why has one got an I/D of 50 mm and one got an I/D of 50.7 mm ? ! ....... Life would be so much easier if ALL du bushes were made in the same place under the one roof ! steven. |
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Post by JonW on Dec 10, 2015 23:01:46 GMT 1
Thanks for your efforts Steven. Bugger on these not being Glacier. I hadnt found the KTM part number, thats interesting, I will research that across my KTM parts sources. I see that it is listed as on 'back order' which is annoying as that probably means NLA :/ Many of the online suppliers still list things as available when they are plainly not, so back order isnt encouraging to see on any ktm part. haha your google search found my post from yesterday on the ADVrider forum where I asked in the forum where people have used these forks on other bikes, it was me who said they were 250 and rare LOL I agree boring these on the coated side would remove the coating, so thats not an option. Im starting to think that making them from something else is the only plan, is it possible to get the DU coating sprayed on aftermarket do you think? Ive no idea on why the sizes differ, but its a good question, this is the pic from the manual, the 2 bushes are ringed in red.  The bush higher up on the pic is the 50.7 one, so is the that sits at the bottom of the chrome fork leg - these are conventional forks of course. |
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Post by steven on Dec 11, 2015 0:31:45 GMT 1
...I haven't heard of anywhere that sprays on any sort of polymer or ptfe type stuff. Where is our metallurgist ? Why cant we use oilite ? .....because it says in wikipedia not to use oilite or its derivatives, on applications that are honed or ground, as that blocks up the pores of the oilite......so how long does that take ? do you do a lot of miles ? so what if the pores are blocked up?...were not really looking for any self lubricating properties, the forks are full of fork oil.......  ? I will track down a metallurgist or one of those material scientist type dudes tomorrow at work and ask one of them what a suitable material would be for this application. steven. |
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Post by JonW on Dec 11, 2015 0:47:18 GMT 1
The 'full of oil' thing is genuis actually Steven, I hadnt thought of that. I guess that fixes that issue, the teflony stuff is really only there as a belt n braces to stop anything marking the chrome perhaps? Well, yes... I dont actually do many miles and this is a motard setup, so its hammered round town now and then, no long runs... its a 37ish bhp single and boring on straight roads  My only thought is if you use oilte or some other such material would it have the same spring characteristics as the OEM bushes which act against the surface they are pressing against as I doubt they ever fully compress... or maybe they do? hmm... and when making them, would a small slit (the width of the cutting blade takes material away from the size of the OD when uncompressed) in them be an issue, im thinking not as these are not sealing anything, just keeping the sliding surfaces apart. Thanks again for your help mate, its truly appreciated. |
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Post by JonW on Dec 11, 2015 1:08:03 GMT 1
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Post by steven on Dec 11, 2015 1:40:21 GMT 1
.....just put girder forks on it.... and you,ll be jammin !
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Post by JonW on Dec 11, 2015 2:13:13 GMT 1
Im not sure they would suit it...  |
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Post by JonW on Dec 11, 2015 7:15:05 GMT 1
Ok, spent another day on this and.... Ive found some NOS ones! Wahooo! Still might be worth investigating this stuff if youre keen Steven, but at least for now my panic is over, PHEW! |
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Post by steven on Dec 11, 2015 17:26:16 GMT 1
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Post by JonW on Dec 11, 2015 22:02:33 GMT 1
Thanks Steven, will be very useful for the next guy to be stuck with this problem.
When I get the NOS ones (I never really think of KTM stuff as NOS, it all seems too new to me LOL!) Im going to fully measure them and record the dimensions before they go in in case I ever need some making.
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Post by steven on Dec 14, 2015 22:10:16 GMT 1
...hi jon,
Good that you found some NOS ones, and we now know what to make them from if ever needed.
cheers.
steven.
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