NovaRossi 21 5 port mods

[Marty Davis]

Hi Marty,

If you can get depleted uranium for the slugs it is better than mallory metal that we originally used. I did have access for a few years as we did the extrusion dies for the 5/8" dia pyrotectic (depleted uranium) projectal that went in the bullets of the Vulcan gun in the nose of the A10's. I mention this as with small cranks it it nice to not have to drill large holes and our best results were using the 2 hole/slug method.

Thanks, John

John:

I have a bunch of Sintered Tungsten (MAllory) so I will just use that.

Thanks,

Marty

Hi Marty,

How are you holding the Mallory metal in? Sometime it would crumble.

Thanks, John

This comes from Ackerman:

No more than half a thousandth or the crank would split.. I would take the

scintered tungsten plug and put it in the lathe and take the dreml with a

cut off wheel and lightly taper the end that was being pressed in.. I would

also take a larger drill bit and chamfer the hole in the crank just a touch

so the plug would start easily.. you can use red loctite and it will hold

the plug... If you remember I never cracked a crank doing this..

John

 

[John Beardslee]

Hi Marty,

For those of you that weren't around when John Ackerman was running, his engines were smooth as butter! He also did alot of work with where to place the bearings in our shaft logs and how many bearings were best, in the days of solid shafts!

Thanks, John

 

[Jack ODonnell]

Hi Marty,

If you can get depleted uranium for the slugs it is better than mallory metal that we originally used. I did have access for a few years as we did the extrusion dies for the 5/8" dia pyrotectic (depleted uranium) projectal that went in the bullets of the Vulcan gun in the nose of the A10's. I mention this as with small cranks it it nice to not have to drill large holes and our best results were using the 2 hole/slug method.

Thanks, John

John:

I have a bunch of Sintered Tungsten (MAllory) so I will just use that.

Thanks,

Marty

Hi Marty,

How are you holding the Mallory metal in? Sometime it would crumble.

Thanks, John

This comes from Ackerman:

No more than half a thousandth or the crank would split.. I would take the

scintered tungsten plug and put it in the lathe and take the dreml with a

cut off wheel and lightly taper the end that was being pressed in.. I would

also take a larger drill bit and chamfer the hole in the crank just a touch

so the plug would start easily.. you can use red loctite and it will hold

the plug... If you remember I never cracked a crank doing this..

John

Hi Marty; John is good with the .0005 press fit.. I drill with a stub solid carbid drill,then use a stub carbid reamer.I end up with a .0006 fit. I use castor oil on the press fit..Have never split a crank or have one come loose . J.O"Donnell

 

[Chris Wood]

just curious from jack john and marty

do you guys really think slugging the crank helps that much? i have mixed opinons on it.. sometimes i wonder if it is a hinder.. more rotating mass..

wouldn't it be more benifitial to try to grind off on one side then to add weight? i realized there is limited area to be able to do this,

kinda like props.. some of the most ugly looking things work.. and there is NO explination why or how.

your thoughts?

chris

 

[John Beardslee]

Hi Chris,

Most cranks have a lot of material removed on the journal (pin) side to compensate for the weight of piston and rod ass'by and if you took much more it would severly weaken it. Like so many things, it is a compromise, with a single cylinder engine you can't balance it for the full range of rpm's. So as the engine is more capable of higher rpm's then you can rebalance so the engine runs smooth in a higher range. With so many variables in race boats, the people that run consistantly well usually are the ones who have worked on every factor to improve the overall performance of their boats.

Thanks, John

 

[anthony_marquart]

This is all very good information.. but I am curious.. What kind of gains are you seeing here? Is all this super high tolerance work gaining 5mph? 10mph? 15? I know it's a hobby,. .and I am really interested, but before I even think about getting this type of work done I would like to understand what type of gains to expect.

Are these boats and engines just flat lapping the regular guy?