bearing bushes for real bearings

[gillybert]

Before you start, this is a bit long but I hope not boring  :

My first PJs had brass bearings & my newest have plastic bearings. Both show signs of wear, which through general use is fine.  My problem is my job, I design drive and instruments for turbomachinery, so I never leave mechanical things I get, as standard.  There's always room for improvement

I have read through lots of threads on these bearings, there's load of good info and Jason's full revamp is superb (www.projumpforum.co.uk/index.php?topic=826.). However, I would like to replace what I can with real ball/roller bearings.

One rule I'm setting myself is not to modify the PJ frame work, which will make my mods undoable (don't know if thats a real word), back to original bearings.  I'm starting with the bearing directly under the footplate as it is the most accessable. 

This is my proposed new arrangement (3D modelled in Autocad Mechanical Desktop).

[youtube=425,350]pwBDHA9K3c8[/youtube]

The parts have been made and fitted to only 1 PJ for comparison.  Makes the framework much stiffer and the joint is silent and slippy.

[youtube=425,350]HvmoxfMFsAY[/youtube]

Detail drawings

Bocked about 6 hours so far on this joint, and its still fine, but only time will tell the real stroy.  I'll keep this thread updated with results and further work.

Sorry its such a long thread

GB...

(i don't think this thread content infringes on any patent as it's only for info, if you think otherwise please let me know)

[Jason]

Nice one gillybert

I love the drawings very professional and well thought out

I did look into ball or needle bearings and I believe one of the expensive stilts uses them but they are set into the frames so require larger holes so managing to retro fit without changing the frames is great

I went for phosphor bronze on the advice of my nightclass teacher (sounds ordinary but he does the work that British Aerospace can't as out works and has won Silver at the Midlands ME show) he said that although the ball/needle bearings will give very free movement there lifespan would be limited due to the constant concusion in a small movement range so for longevity the bronze was the way to go as you got a larger bearing area and I was going for not having to replace them

Having said all that your design will be useable by everyone and the bearings should be easy to replace so well done mate you could have a "Retail item there"

Aside do you do your own machining

Jason

[webmaster]

Sorry its such a long thread

Are you Mad?! It's people like you, Jason, Pinhead69 that take the time and effort to create mods like this, that make the product, overall design and experience better for others! So keep them coming, don't worry if it makes you sound like a geek  lol

Back to the actual mod...
The mod looks solid and I'll be interested to know how it works for you and how long it lasts, I remember someone doing this in America and apparently it worked really well, the guy was called Lee  his webby was PoweriserMods.com but it is now down so I cant actually see if it was the same and I'm going from memory...

If they work well, and it's something you can easily make, feel free to list them in the classified - Mods Section 

Wicked drawing by the way!

[gillybert]

Jason, Didn't know if I'd gone a bit OTT with the thread content, its an occupational hazard.  This type of design & detail work is my livelyhood, so I hope I've not got it wrong  (http://www.rotadata.com/digital-telemetry.htm).

Plain bushes are the ideal solution for PJs if engineered & fitted right as you did with yours  , but alas, that kind of mod not available to all.

I'm not sure that the bearings see a true concusive load, as I hope its a more a quick progressive load due to the springs, and no load on the bearings can actually exceed what your legs can handle without your legs snapping.  The bearings I have used can handle 400kg (8 times my body weight, that would snap my legs first).

I might have it really wrong and missed something dead obvious - opps, have to wait & see  .

All that aside, if its an acceptable mod with good life, as you say, open to everyone.

Machining wise, I do use the machine shop at work when I get time, but this first set of parts was made by the lads in the shop for me 

GB...

[gillybert]

Naz, Of course I'm mad, I love bocking  :

I'll keep the thread updated as testing progresses (or fails), and I'm moving onto the top spring bearing next.

I found the PoweriserMods.com link, but nothing at the other end  , would have been useful I think.

GB...

[Dark Knight]

You stole my designs   
I've not very good with CAD but that's how I was got to fix my oversized bearings for my project 

[webmaster]

lol

He can't steal something you haven't shared with us DK 

[Jason]

I think you have got it dead right GB you are designing for the real world (a reasonable lifespan and ease of fitting/use)and most people would be unable as you say to get the sort of fit I went for on the ph/bronze bearings and mass production would be to expensive
Whereas your design is ideal for mass production and home fitting (Idiot proof hopefully )

The chap that teaches me at evening classes (15 years of them now) tends to work on "Mission Critical" components for things like Martin Baker Ejector seats and Harrier jump jet instrument pannels so he tends to go the perfection route rather than real world affordable I mean when your planes on fire and you pull that lever you want it to work so who cares if it cost a fortune  

And for me your post was'nt to long I like loads of info and found it very interesting and informative (make the next one longer )

As for the concusive loads as you say only testing can tell but I think they should outlast the plastic ones by many many hours and as they are easily replaceable and relatively cheap it's not a problem anyway so you are on to a winner there mate

Keep on inventing looks like your good at it

[Dark Knight]

lol

He can't steal something you haven't shared with us DK 

I'm rubbish with CAD ( if I had one one this PC ) It's all still in my head. give me until Xmas

[webmaster]

I totally agree with Jason. All the info you can give makes it more worthwhile and a top read!

Also as you have the older gen, as well as the latest gen, plus your old design, you're actually in a better position to compare the different versions too

@Jason I actually did do research into what you did and you're right it does get very expensive!

[Jason]

Tell me about it Naz I just bought some more bronze and it so expensive I won't be eating this week add to that 6 hours + machining and it's cheeper to buy a new set of PJ's

I don't know how you can sell PJ's at the price you do but I'm glad you can 

[webmaster]

I have no idea 

Oh the subject of your bearings, are they still as good as or have you noticed wear? You've had them on for a few months now isn't it?

[Jason]

Still as tight as the day they went in they run free but you get no rattle

I have done the 2 bottom ones as well now and the best bit is they are quieter when I land from a jump I don't get that slapping sound

I must admit that it would be the second mod I would do right after the cuffs

If you make it to CiN you can try them

[gillybert]

Cheers for all the positive feed back guys & gals 

@DK, feel free to steal right on back 

@Naz, having older & latest gen has highlighted an immediate difference.

Plastic bearings won't last as long as the earlier brass ones.  The problem is the fit of the plastic bearings.  Ideally the bearing bush should stay stationary in the frame, and the tube should rotate inside it.  What happens with mine is the bushes are a tight fit on the tube, then and the bushes & tube rotate inside the frame holes.  These holes being pressed, wear the plastic quicker than the aerlier brass  .

I'm working up a simple DIY improvement to this, which hopefully anyone can apply before their bushes wear to much.  It won't involve any new hardware I'll post it when I've tried it.

GB...

[webmaster]

I'm working up a quick DIY fix to this which hopefully anyone can apply before their bushes wear to much.  It won't involve any new hardware I'll post it when I've tried it.

That would be great! Thanks 

[Jason]

I'm lucky at work as I get to chat to the Bockers in Lord of the Rings and see the Powerskips they use and guess what Powerskips use Plastic bearings

They don't seem to have a wear problem with them and the only difference I can see is that the holes in the frames are bored not punched so the fit is better so I must agree with you GB the problem is movement of bearings within the frame

I solved it when I used the plastic ones by using Locktite Bearing Lock to glue them in trouble is it's not easy to get you have to go to a decent bearing supplier to buy it I did think about epoxy to set them in position but as I had the bearing lock I did'nt bother

[gillybert]

.....and guess what Powerskips use Plastic bearings

...I did think about epoxy to set them in position but as I had the bearing lock I did'nt bother

Jason,

.....If Powerskip can make plastic bushes work, so can we 

...Yep thats what I'm going to try, but to use a high strength epoxy which is water, oil & solvent proof (from eBay), normal araldite isn't. This will also gap fill to ensure the bush OD is fully supported in the dodgy frame hole, which should limit the deforming of the bush.

 Also, the bolt tubes need polishing to be a nice sliding fit in the bushes, not the press fit as mine were 

This is only a stop gap fix until I get round to a more sound fix, but if it proves OK, I'll post a simple tutorial.

GB...

[Jason]

Sounds good GB
That is one problem with punched hole as the punch wears it can deform the holes to the extent that they are anyting but round and as the sharpness goes the holes enlarge strangely (you'd think they would get smaller) thats why I reamed all the holes to make them uniform

And yes I agree the tubes need polishing to make them wear less a run up in a drill and some autosol should do it

I did think about looking into the cost of mass produced PTFE or sintered bronze bearings (dont know how either stand concusion) but with your conections you might be in a better position to get a good price

I'll look forward to the tutorial

Jason

[gillybert]

Right, I've now gone and done it.   

Both my PJs have this bearing arrangement directly underneath the footplate now.  I'm going to see how they go for a couple of weeks and then report back. 

Please remember, I haven't found out yet whether these work, or for how long they last, it might end up being an unmitigated disaster 

I will post back with results.

I've also applied the epoxy upgrage to both spring top and lower vertical support bearings as I mentioned earlier.  Will see how they go aswell.  Should improve frame stiffness and reduce wear.  Will post a simple tutorial is the mod helps.

Here's hoping 

GB...

[masterking09]

i was wondering if you could tell me the dimensions of all the parts and if you could tell me the total price and where to get the parts
thx
masterking09

[gillybert]

Hey masterking09

Cheers for the interest 

All the machining drawings with dimensions are at the start of this thread, along with an assembly drawing.

Couple of points I need to make though:

1. The Bearing Spacer GB10002 I found needs dressing on assembly to fit in between bearing inner races.  It needs to be a snug push in fit, but not hammer in tight

2. I have applied high strength epoxy to the back of the bearing cups (as used in my thread http://www.projumpforum.co.uk/index.php?topic=1271.0 ).  This was to make sure the cups didn't rotate 

3. The Thrust Washers GB10004 were lapped on some wet & dry paper to trim their thicknesses so as not to clamp up tight when tightening up the bolt  Also applied copper grease to both sides of the thrust washers.

Points 1 & 3 I will address in the part drawings eventually, and point 2 will be noted on the assembly drawing.

The bearings I bought from ebay, I got 10 for £4.80 inc delivery (just search for "608 2RS"), the other machined parts I had made at work, so I can't price them up, soz 

They have now had around 8 hours of use, and still feel secure, and play free.  The other bearings in my PJs have had my "Epoxy bonding of plastic bushes" mod done to them, and they are also holding up very well.

I may very well resort to just the "Epoxy bonding of plastic bushes" mod on future PJs, and not go the whole hog of ball bearings as its a simpler mod, seems to be OK and only costs a bit of glue (eBay) and wet & dry paper 

I hope this helped, but if not, soz, I tried  No kidding, If you need anymore info I can help with, please just ask, I'll do what I can to help.

(Oops, sorry for the long reply)

Cheers

GB...

[masterking09]

thank you for relying.  i really appreciate it.  did epoxy bonding the old plastic bushings work well?  did it take away the squiking noisesand did it make it so that the bushins dont use up as fast?  so basically did it make a difference in how the stilt preforms and what did it change?
thank you
Masterking09 

[Sx Nutta]

thank you for relying.  i really appreciate it.  did epoxy bonding the old plastic bushings work well?  did it take away the squiking noisesand did it make it so that the bushins dont use up as fast?  so basically did it make a difference in how the stilt preforms and what did it change?
thank you
Masterking09 

Gillybert has only just done it, so it is a matter of testing over time, as for squeaking, I will be putting a up a post soon, to explain how to reduce or stop this problem!!

[gillybert]

Nail on the head Sx, only had 8 hours testing so far, so too soon to say either way 

What I can report is that after the 8 hours, the bonded bush joints appear not to have worn, or become loose  .  Sx is right, they do need longer testing, but it is looking promising 

My aim was to stop the bush rotating in the frame and allow the tube to rotate in the bush, not the other way round.  In theory, this should increase the bush life 

As for squeaking, this pair of PJs have never squeaked, I did spray everything with WD40 before I ever used them, then used them for 2 hours before I bonded the bushes in.  So I don't know if bonded bushes reduces squeak 

I will keep the Bonded Bush thread updated with progress 

GB...

[Sx Nutta]

That would be great GB, as I may be making metal bushings to stick on mine with epoxy, just want to see how well they do after 20 to 40 hours use!!