Crankshaft silicone

What kind of silicone is good for the crankshafts?

One of mine is expanding and starts to break into smaller pieces.

This is a genuine NR shaft.

The silicon will expand if you use wd40 or similar products..just cut out the silicon the engine will run fine without it.

I suspect WD40 to be guilty for this.
I found some stuff and filled it up, let`s see how it holds. Next time I will leave without stuffing and see what happens. Thanks for input

Joern,

We found no difference with or without the silicone ramp in on the water testing.

Cars and Planes have a much different load on our motors then the water we race in.

And Jim your engines are pretty much one off custom engines that are similar to a F-1 engine.

I wonder why they use silicone if J-B Weld is a better product for this application?

The engine manufactures maybe using the silicone to help balance the crankshaft also?

I am sure there is a reason why they use it besides just cost? Would it be better if they just

machined the ramp into the crankshaft when they are making them? Interesting subject Jim.

Thanks For Reading,

Mark Sholund

Joern,

Does anyone think that an engine manufacturer of a high performance racing engine would waste the time & money to put something in an engine for no reason? I definitely can not speak for any NR front intake crankshaft. However, I am absolutely sure from many bench & data logger tests of the Nelson .45 long stroke, front intake engine, "that a properly shaped ramp", when inserted with J-B weld will allow the engine to "turn faster & pipe up easier". We see an engine RPM increase on the high end of 200 to 400 RPM as well as the plane piping up easier when it leaves the ground on take off. We have experimented with many different compounds, including various silicones, unsuccessfully! When the ramp's shape is predetermined with a machined linen based phenolic piece, which is glued in place with J-B weld & then coated with J-B weld, the ramp remains for an indefinite period of time. Solvents & oils have no effect on the cured J-B weld material. The posted photos show how the crankshaft needs to be roughed up in the area where the ramp is to be glued in. After first glueing the ramp in, it is then coated with a very thin layer of J-B weld. Both operations are cured in an oven at 125* F. Notice how smooth the final ramp is & how consistent the shape is from the method used.

Jim Allen

Very nice Jim!!

Brad

brad nichols said:

Very nice Jim!!

Brad

Click to expand...

Brad,

We also take time to remove any small burr that is found on the crankshafts induction hole that is a result of the machining operations. We remove these burrs after the crankshaft has been hardened to prevent them from breaking off when the engine is running.

JA

I use atf mercon or dextron as after run oil in my ramped engines, never had any problems with the ramp swelling or coming apart, i dont think the ramp is for wot only, i think it helps when milling mid range throttle and wot throttle. Rc 90 boat.

Jim Allen said:

Joern,

Does anyone think that an engine manufacturer of a high performance racing engine would waste the time & money to put something in an engine for no reason? I definitely can not speak for any NR front intake crankshaft. However, I am absolutely sure from many bench & data logger tests of the Nelson .45 long stroke, front intake engine, "that a properly shaped ramp", when inserted with J-B weld will allow the engine to "turn faster & pipe up easier". We see an engine RPM increase on the high end of 200 to 400 RPM as well as the plane piping up easier when it leaves the ground on take off. We have experimented with many different compounds, including various silicones, unsuccessfully! When the ramp's shape is predetermined with a machined linen based phenolic piece, which is glued in place with J-B weld & then coated with J-B weld, the ramp remains for an indefinite period of time. Solvents & oils have no effect on the cured J-B weld material. The posted photos show how the crankshaft needs to be roughed up in the area where the ramp is to be glued in. After first glueing the ramp in, it is then coated with a very thin layer of J-B weld. Both operations are cured in an oven at 125* F. Notice how smooth the final ramp is & how consistent the shape is from the method used.

Jim Allen

Click to expand...

there is no doubt that the silicone is there a reason. have ran .12's and .21's for over 20 years in on-road cars and the throttle response and spool up is so much faster!!! i clean out my motors with LPS 2 and have never had an problem ever!

RC 90 Boat said:

I use atf mercon or dextron as after run oil in my ramped engines, never had any problems with the ramp swelling or coming apart, i dont think the ramp is for wot only, i think it helps when milling mid range throttle and wot throttle. Rc 90 boat.

Click to expand...

That's very interesting - how long have you been doing it for? I've always paid through the nose for dedicated 'after run' oils, when I could pick up a liter of Dextron 3 for £10...

I've been using corrosion x to flush out the engine and as the after run oil for 2 years now on a Novarossi 12 silicone ramped crank with no problems. I was recently told by a fellow racer that he has used rislone engine treatment for after run oil in a Nova 21DD for several years with no issues. That engine has a silicone crank as well. I remember reading somewhere that some onroad racers believe it's the propellant used in many of the aersol spray oils that can attack the ramp because of the solvents in the propellants?

Thanks for input, guys, I appreciate it.
The purpose of the ramp is qiut obvious to me, however I have never tried the difference with or without. This is first time I experience the silicone to expand, and I have a huge number of engines with siliconeramped cranksshafts.
Maaany years ago I used CRC 5-56 to wash out the engines, but that stuff left me with expanded silicone o-rings for sure, then switched to WD40 and CRC 6-66 which has been working fine for me.
I was close to fill up with J-B weld, but found some stuff that is supposed to handle oil and alcohol, let`s see how it goes.

Jim

How about machining a delron ramp and pressing it in the crank.

Dave

dave roach said:

Jim

How about machining a delron ramp and pressing it in the crank.

Dave

Click to expand...

Dave,

I'll explain about other techniques we tested to put theses ramps into crankshafts. However, there was no machined piece that could be pressed into the crankshaft because of its shape inside. We machined the ramp into the crankshaft itself on some test pieces, but this created a out of balance problem. We also made teflon molds of the ramps shape that were inserted into the crankshaft while the J-B weld was still in a liquid state. After the J-B weld was cured the teflon mold could be easily removed. This method required a fair amount of clean up time because of the excess J-B weld that would be trapped between the mold & the ID of the crankshaft. It is a proven fact that the glueing of ramp shapes made of delrins, nylons & plastics to metals is difficult or impossible without using special adhesives. These adhesives are very costly & they have a very short shelf life.

Jim Allen