PEERPSI

Can't seem to get one that lasts. I've tried brass, oilite after wearing out the originals. I grease the shaft before putting it in. Also the thrust washers wear out as well. I tried making spacers out of Delron but in 3 outings, 5 tanks of fuel it's worn 3/16" off of the spacer. I think the only thing keeping it from wearing out more is the fact that it closes the gap and ends up pushing on the stuffing tube. Ideas?

martno1fan

Something doesnt sound right to me,your bushings should last quite a while,ive not changed mine in a year but i dont run every week.I have heard that the brass ones will last several seasons of hard running.
Mart

PEERPSI

I'm thinking I have too much prop shaft passed the strut. I have minimal clearance when installed but now I'll bet it's at least 25 thou.

pyro1

Warehouse Hobbies sell a self lubricating bushing. Check them out they are a little larger in diameter & a bit longer.Tony has full instructions on how to install them.




http://9x4br.64n2f.servertrust.com/P...uctCode=RH1030

martno1fan

Your running a square drive i asume seeing as theres no gap?.
Mart

Dockman

Is there a chance you don't have enough gap (I have about 1/8" or so, no less) between the thrust washer and strut? Not allowing good water circulation through the shaft?

PEERPSI

Picture doesn't show gap but I allow roughly 1/16" total gap. I usually allow an 1/8" at the stuffing tube so that it's pushing on the strut not the stuffing tube.

I use oillite material to make the bushings which is the self lubricating material that WHH might be using if not it would be similar.

I've changed my spacer to Delron which I think was too soft so I've gone back to a harder PVC plastic. I made a new one just now and I've reamed to .250 and lapped in the shaft to bushing. I have about 5 thou wear on the prop shaft but the bushing had a bore of 45 thou over or 22.5 thou clearance at it's worst spot.

I'm also going to try a dry graphite lube to see how that works out.

As for water cooling this is a surface drive, only 30 % of the prop should be in the water when it's at speed so that means the bushing shouldn't be in the water once you're up and running.

I had been using center saver grease for lathe live centers. It's supposed to resist water and not fling off. It definitely does not fling off! I use it on the flex shaft as well and after a run it's all stuck to the ferrule.

Oh, yes square drive at both ends.

Dockman

Speed coat (Lubri Bond) everything.

Dockman

I bought my brushing from WHH and they claim they are coated with something. Don't know what it is, but I could tell they were coated.

PEERPSI

Not sure were they get them but here's an example from McMaster Carr.

http://www.mcmaster.com/#60695k61/=39drkm

They also have these graphite lubed thrust washers. Unfortunately nothing in the size I'd need.

http://www.mcmaster.com/#oilite-washers/=39dsyd

This is a link to the stuff I've been using.

http://www.bowman.co.uk/

Bbbutch

Have you checked your props to see if they are balanced?

Dockman

Good point.

PEERPSI

Professionally balanced by senoir Hoffman of Dasboata.com.

I spent a little time looking at the specifications and calculations for self lubricating bushings. The only ones I could find online that were capable of the rpms we turn were stainless steel cased, bronze filler with lead and PTFE coating on the surface. They' ae are available from a company in China though not in the volume I would need.

The issue isn't the force we put on them it's the speed, most are rated for 400 fpm. At a maximum of 20000 RPM our shafts are doing 1308 fpm. I think in my situation the surface roughness of the prop shaft is the issue.

I'm going to get a new strut from WHH and try their bushings to see how I make out. For now I'll just run what I built today.

patriktegelberg

Edited: I missed some info, sorry.

Hesco Racing

Here's a question. in the pic showing the strut It looks like the bush runs all the way and not with a gap in the middle as in 2 bushes. Or have got the wrong side of it. Iff you have one long bush it would wear out quicker than having 2 bushes. A great material for thrust washers is PEEK, been using it for years on FSR-V boats which runs on the thrust washer and not on the shaft like out-drive boats.

Closest I could find in Canada
http://www.paplastics.com/ketron.htm

Cobus

PEERPSI

Bushing runs all the way through with a thrust flange on the prop side.

Hesco Racing

Split it into 2 shorter bushes and it would last longer.

Cobus

black talon

My Feedback: (5)

i would still check the props balance.

PEERPSI

Prop was professionally balanced and sharpened by Dasboata but I could still check.

I've got two new bushings coming in from a manufacturer as samples. We will see how they work.

martno1fan

My thinking as well.Regards bushes make your own from Brass all you do is flare one end so it wont slide right inside the stuffing tube then run the tube all the way through the strut.For yours to be wearing out so fast there is def something wrong im certain and i dont think its the bushes .
Mart
[link]http://www.modelgasboats.com/Magazine_Content/How-to_Articles/Make_Your_Own_Strut_Bushings/[/link]

PEERPSI

I've been making my own on the lathe using oilite.

dicko

If your prop is balanced, check to see if it is straight, you may have hit something that has altered the cup, pitch or offset of one of the blades, that will be as bad or worsethan an unbalanced prop. Have you tried a different prop?

I use thrust washers and needle bearings on my square drive cables.