ORIGINAL: archyroof
Hi guys,
I have been grappling with how to get a combination of large capacity engine, light weight and cheap fuel consumption. Generally speaking gas engines are more complicated, more expensive and heavier but cheaper to run. Conversely large glows are cheaper to buy, simpler, lighter but dearer to run.
Have you guys discussed or thought about adding needle bearings to a glow motor so it will run with a much lower oil content in the fuel mix? Say 40 or 50:1.
This would allow for a simple methanol/oil mix compatible with the existing engine's parts/fuel lines etc and would alleviate the need for plug conversions, presumably timing issues would not exist and there would be no need for 'exotic' fuel mixes.
I realize this solution would be limited to about 35 cc (the largest glow motors currently available). The Moki/Mark 2.10 springs to mind as an option.
Your thought would be appreciated [8D]
Yes, here,
http://www.rcuniverse.com/forum/m_45...page_23/tm.htm
We have discussion about running diesel engines on a no ether based fuel. Later posts include various oils and low oil mixes. The issue is the plain bushed rod. The bushed rod at the crank is not so much an issue maybe because this end gets LOTS of fresh fuel/lube and the pin rotates through 360 degrees for effective distribution of lubrication. the pin at the piston end only oscillates through a shallow angle and does not get a lot of fresh lube circulating. This is really where we need a needle bearing. Illustrated is a rod from the old Webra .60 Blackhead. Note the needle bearing at the piston and not at the crank. This worked very well for many, many gallons of fuel. The piston pin wear is non-existent but note that there is ALSO no wear at the crank end. And the crank end is plain, brass bushed.
So the solution to a 50:1 mix, glow, gas or diesel seems to be in getting that piston pin a bearing of some sort. Here,
http://store.microgroup.com/catalog/...talog_5-16.pdf you can get very small, thin wall tubing. The idea is to use the right size as the outer race along with needles made from .015 piano wire running directly on the pin. This would be full complement, without a cage and free floating. Maximum number of needles in a compact space. As such, we can make up a needle bearing for an engine as small as the Norvel .15 as discussed. But the problem is getting the tubing. An attempt to do so was met with minimum quantities, minimum billing etc. Am looking for another source.
But the Tanaka, with bearings all over, will be dieselized and 50:1 diesel fuel mixes will be tried along with exotic gas and glow fuels. I've even had luck in running an all Biofuel mix in the small .15. That's with NO added lubrication, only 100% Biodiesel acting both as fuel AND as lubrication. Sure enough though, the rod wore out at the piston end but there was no wear whatever at the crank end.