Needs Pictures: 0
Results 16 to 30 of 32
-
30th Apr 2022, 09:20 PM #16
hi BobL,
Got one of those as well.
It was the predecessor of the current Hoselink 2 outlet tap.
My Holman was much better than yours- leaking profusely straight out of the package .
Grahame
-
30th Apr 2022, 11:12 PM #17
A week or so ago, I had to rebuild our 12 months old lawnmower, that started burning a lot of oil.
So I ordered some new rings and pulled the engine down. It is a 150cc "good old" Briggs & Stratton engine in a "respectable" brand Victa.
When I had everything apart, I couldn't believe my eyes: the CAMSHAFT WAS PLASTIC!
So were the gears that drove it. So is the entire starting mechanism.
The aluminium piston runs in a bare aluminium bore, the big end bearing is the aluminium conrod, the crankshaft is grey cast iron, the pushrods are 4mm dia. steel tubes, the rockers are pressed sheet metal. The piston "skirt" are two very narrow slides only, and the piston top finishes at the bottom of the oil ring groove, with cutouts so the oil rings are actually exposed in those spots to the crank case.
Anyway, so after a year's use - at a rate of about once a month, taking maybe 1-1/2 hrs each time, the ring gaps were around 1mm.
I fitted the new rings which closed the gaps to around 0.3mm. Checked everything else for wear (negligible) and reassembled everything.
The mower runs fine again.
Now I'll keep real tabs on its actual use and see how long it goes for.
This is by far the worst engine design I have ever seem and the shittiest $500 mower I have ever owned!
My last mower was a ($295 in 1986) Honda Buffalo that lasted and worked fine for 35 years. I wish I hadn't given it away and rebuilt that instead.... or bought a (now $1100) Honda Buffalo again....Cheers, Joe
retired - less energy, more time to contemplate projects and more shed time....
-
1st May 2022, 12:04 AM #18Most Valued Member
- Join Date
- Apr 2012
- Location
- Healesville
- Posts
- 2,129
Joe that would probably be an ill fitting ac element or often a shrub branch or stick can push or pull the breather tube off at one end or the other and the engine gets dusted out. Also use only SAE30. Briggs have used alloy cylinder bores for ever, except the IC engines (industrial commercial) that have cast iron sleeves. When re-ringing you never hone or abrade the alloy cylinders as the new rings will pick up the bore, the cylinders can be rebored and honed but the hone was something special that i never had eyes on.
A number of small engines use plastic cam gears now, when i first seen the single cylinder 17-20 hp kohler engines i thought it odd that the plastic cam gears were never a problem but they often got a cracked crankcase, haha and this went on for years, dunno how many short engines that i replaced under warranty...
-
1st May 2022, 08:04 AM #19Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,561
UV resistance in plastic depends a lot on the formulation and of course, the additives that give it UV resistance (usually Titanium Dioxide I think) cost, so they are not added if not needed - as our Engineering Manager found to his embarassment after reviewing product test results before release (with the plastic grade he personnally selected)...
The best 'natural' colour for UV resistance is Black, as the light does not get in as easily.
Michael
-
1st May 2022, 09:16 AM #20Mechanical Butcher
- Join Date
- Oct 2004
- Location
- Southern Highlands NSW
- Posts
- 1,898
We know that generally you can't use the same metal bearing against itself, exception being cast iron.
But many car and motorcycle engines and air conditioner compressors use what seems to be aluminium alloy parts rubbing together successfully.
I believe the trick is to use an alloy with lots of silicon in it, then treat a surface with acid so as to deplete the top layer of aluminium, leaving hard silicon.
-
1st May 2022, 10:05 AM #21Most Valued Member
- Join Date
- Nov 2017
- Location
- Geelong, Australia
- Age
- 57
- Posts
- 2,669
Interesting - I haven’t heard of that before. I always assumed it was just the lubrication that kept the surfaces separated.
Steve
-
1st May 2022, 10:50 AM #22Most Valued Member
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 3,228
-
1st May 2022, 12:32 PM #23
My biggest surprise was not the cam gears, but the the camSHAFT. The actual shaft and cam lobes were plastic.
Thanks Shedhappens for the hint about checking air cleaner fitting condition in the future.Cheers, Joe
retired - less energy, more time to contemplate projects and more shed time....
-
1st May 2022, 01:05 PM #24
Bakelite
Is bakelite used much these days ?
-
1st May 2022, 05:49 PM #25Most Valued Member
- Join Date
- May 2011
- Location
- Murray Bridge S Aust.
- Age
- 71
- Posts
- 5,959
Found this on google for you;
Bakelite continues to be used for wire insulation, brake pads and related automotive components, and industrial electrical-related applications.
To grow old is mandatory, growing up is optional.
-
1st May 2022, 05:56 PM #26Gear expert in training
- Join Date
- Aug 2008
- Location
- Melbourne
- Age
- 34
- Posts
- 1,079
We still make fibre-reinforced-bakelite (Tufnol) gears. They're often used as mechanical fuses in machinery, similar to a shear pin.
Gear cutting specialists and general engineers www.hardmanbros.com.au
Fine pitch gear cutting from 0.1 Module www.rigear.com.au
-
1st May 2022, 06:34 PM #27Philomath in training
- Join Date
- Oct 2011
- Location
- Norwood-ish, Adelaide
- Age
- 59
- Posts
- 6,561
As Elan says, Bakelite is still used, but is a Thermoset plastic - made in a different way to most common plastic items and won't melt. But it is expensive, abrasive on tools and the dust is not good for you (phenolic compoounds). I think it eventually dries out in the sun and gets brittle or cracks though.
Michael
-
1st May 2022, 09:17 PM #28Diamond Member
- Join Date
- Aug 2019
- Location
- Revesby - Sydney Australia
- Age
- 57
- Posts
- 1,195
Joe's comment about the plastic camshaft reminded me of a Kmart mower (Gardener's Choice) mower I stripped:
IMG_2275.jpg
At the time, was intrigued that it had plastic gear and lobes. At least the cam shaft was metal, and the bores were iron, alloy cylinder cast around it.
I share your concern about the starting mechanism (pulley, ratcheting pawl) being plastic - from memory it was well worn.
Interestingly, the camshaft seemed wear free. The Nylon they used, or the oil splashing around in there, seemed up to the task?
P.S. This is what failed:
IMG_2276.jpg
Mower had oil leak around main crankshaft seal. Previous owner had mown some long fibrous grass (flax?), that was stuck in there, so it might have been lubricant free for many hours operation. I replaced the seal and refilled crankcase, but when it got hot, it would drop power or die. Eventually seized.
-
1st May 2022, 09:52 PM #29
Michael alluded to the quality of plastics and correctly matching them to the application.
The Blue spare parts container is an Aussie Fischer plastics parts container.
The red one from my Chinese made mobile frame with various sized parts containers and various bin colours. Frame was always IN THE SHED out of the sun.
The front fell off it when I unclipped it from its mobile frame. -about 9 years old
The blue one has been kicked around, dropped, walked on, crushed and generally mistreated for near twenty years. Its tatty,but intact. Michael was sooo.. right about the colour and UV effecting it.
Grahame
nasty asian bin.jpgOlder Fischer bin.jpg
-
1st May 2022, 10:56 PM #30Mechanical Butcher
- Join Date
- Oct 2004
- Location
- Southern Highlands NSW
- Posts
- 1,898
Liner-less aluminium alloy engine blocks had been in mass production in USA before the Germans developed Nikasil, which I think is an improved development.
I'm not sure if the Repco-Brabham V8 F1 engines were linerless, but the Oldsmobile F85 aluminium blocks they were based on were. That's from early 1960s.
Similar Threads
-
Vintage car re-metal white metal bearings
By morrisman in forum METALWORK GENERALReplies: 45Last Post: 17th Apr 2024, 07:14 PM -
Douglas Metal Shaper and Bramley Sheet Metal Folder
By bwal74 in forum METALWORK - Machinery, Equipment, MARKETReplies: 5Last Post: 31st Jan 2016, 12:25 PM -
DONE: Metal Cut-off Saw
By Alby123 in forum METALWORK - Machinery, Equipment, MARKETReplies: 1Last Post: 4th Jan 2013, 04:31 PM -
What metal do I need
By miles and jules in forum METALWORK GENERALReplies: 41Last Post: 13th Mar 2007, 10:27 PM -
Best way to slide metal over metal?
By aceofspades in forum METALWORK GENERALReplies: 9Last Post: 29th Mar 2006, 12:53 PM