SrTelemaster150

Anyone have any experience doing this. I want to bush the big end of an FA 180 rod to use it on an FA 150 crank pin. The displacement will only be .07 cu in less on the 150 crank. (1.71 cu in compared to 1.78) If I use the 150 rod it will lower the CR to 8.1:1. Using the longer 180 rod bushed down to the 150 crank pin will yeild a healthy CR in the neigborhood of 13:1.

All this is based on 180 pot/piston on the 150 case W/a deck that is .052" shorter than the 180 case deck.

I have a 180 crank, but I just wanted to do an experiment W/the 150 crank. The 180 crank/rod/piston in the 150 case will have a CR of 15.1:1. A bit high even on electronic ignition W/methanol fuel.

W/the 180 crank I'll have to make a .010" "stroker plate" for under the jug to lower CR to 13.6:1.

TFF

http://www.modelenginenews.org/ has a lot on model engine machining.
You would need a fixture to index the small end so the big end would be parallel. You would probably need to square up the big end hole and then make a bush with the right fit to press in. Then you can drill and ream to the proper fit. Depends on if your using a lathe or a mill or both. With all that you can make a rod the correct length and with the right holes.

SrTelemaster150

I'm trying to do a modification that will be cost effective for someone that doesn't have their own machine shop. Machinig a new rod out of a hypereutectic forged aluminum blank would not be cost effective if the entire job had to be farmed out. Having a bushing made to the proper OD & (slightly small) ID before hand, then heating the rod to 300*F in the oven/freezing the bushing would make an easy press. fit.

Hopfully, after drilling the oil holes & making the slit through the bottom, that proceedure would require minimal finish reaming as the rod shrinks on the bushing & reduces the ID only slightly if @ all.

I am most concerned W/using the proper alloy.

earlwb

Well you'll have to bore out the old bushing to some extent as you have to make it square again. The holes tend to become slightly oval shaped and tapered from end to end with use. Then machine a new bushing to fit and install it. Then bore out the hole in the middle and ream it to size. So you'll need a lathe and or a milling machine to do it. It could be tricky getting the new bushing to fit just right without having the rod crack on you from the stress of getting the bushing reinstalled.

SrTelemaster150

I'm going to use a brand new 180 rod. There is no bushing in the FA 180 rod. The 180 crank journal is 9mm, the 150 8mm. I think a .5mm bushing wall thickness will be sufficient if the rod is heated, the bushing frozen & care is taken pushing the bushing (quickly) in W/a chilled pilot.

I use to use this proceedure W/removal & installation of Harley Davidson "Big Twin" valve guides & it only took a few light taps W/a plastic mallet to seat the chilled guides in the 300*F head castings. You only get 1 shot though. You gots to be ready & make it work the 1st time. On such small pieces like the 180 rod/thin bronze bushing, once the rod shrinks & the bushing swells they are pretty well locked tigether.

I am willing to pay to have the bushing turned, bored perhaps .1mm undersize. I will do the installation. drilling of the oil holes, slots, etc Then pay for the finish ream.

Again, what would be the proper material for the bushing?

earlwb

Well you normally use the special alloy "bronze bearing" material. it is somewhat porous and allows oil to soak into it.
For example http://www.onlinemetals.com/merchant.cfm?id=760&step=2

N99JH

My Feedback: (66)

Have you considered using a K&S metric brass tubing? I think that the wall thicknes is .5 mm and they probably have 9 mm OD so the ID will be 8 mm. I do not think that the brass will be inferior to the 6061T6 aluminum that most conrods are made from in terms of durability.

Broken Wings

My Feedback: (20)

Been there.....

I had to make a new rod for one of my old engines, it's still running...

Here is the link to the post.

http://www.rcuniverse.com/forum/m_72...tm.htm#7273524

Let me know if I can help you out.