Homemade milling machine well kinda.. Connecting rods 998 and 1098
Turbo Mini Forums

for my 1098 based turbo build would like to see 150-160 so bring on the boost

well as above i have made a jig to lose some weight on my rods i think its done a cracking job but now i think about it i may have gone a bit to skinny?

im i right to think 95% of the forces on the small end are pushing down the beam so its quite safe to go this thin on top? is it only the weight of the piston getting puled down ie drag from the rings and piston that will have an effect on the rod as boost while the intake is open will be pushing the piston down on the intake stroke well most of it?

EDIT: some scales are on their way also the size from the bush/pin surface to the outer edge is 0.130" and the wall is 0.055"-0.060"

pics as we all like them.. tell me what you guys think good or bad hell id rather get abused at this stage than have the rods exit the block!

this rod is a trial and it dose really matter to much but its always a bummer to destroy a good part !

Edited by Turbo This.. on 14th Sep, 2012.

Bin them! Sorry.

skip time sorry mate there no good

give em hell

ok so i have done wrong buy what?

i cant do a good set if i don't know what or how ive done wrong come on guys this is about helping and teaching

is it just to thin? if so its easy to slide the cutter into the chuck some more and that will take less off.. (i guess what i should have done to start with..??)
is a burr no good for removing material?

A novel way to remove material and be consistent across all the rods...
It does look a little thin, but it isn't thin all the way across, so maybe it will be ok?
I know I wouldn't have risked removing that much - but I don't know if the 1098 rods are weak or will stand some tweaking... See what others say for sure.

thanks dave

yeah i think ill take far less of the rods for the build basically just enough to get a constant thickness all the way around

inertia forces as the piston mass is accelerated back down the bore is the time of peak stress on the rod. Taking meat of the little end like you have would be the last place I'd look at.

Ask yourself this: Without the necessary test equipment to validate the strength of the modified rods, is it really worth the risk when it will most likely cause a substantial amount of damage if that lets go?

inertia forces as the piston mass is accelerated back down the bore is the time of peak stress on the rod. Taking meat of the little end like you have would be the last place I'd look at.

Ask yourself this: Without the necessary test equipment to validate the strength of the modified rods, is it really worth the risk when it will most likely cause a substantial amount of damage if that lets go?

adcyork what you have said makes a lot of sense
a lighter piston would stress the rod less thus making rod modifications less drastic on rod strength but as you say do to much and things can quickly go very badly

im sure there is a margin for error in the factory casting so surely taking the casting back to a more uniform shape shouldn't hurt it that much? provided the lowest point is not past the point of strength witch is waht your saying i just dont know if its to far to cause damage or not

anyone have some idea's on testing them?

I too like what you have made but the little end is the last place i would remove material looks neat though

Yes i moved to the darkside

Instagram @jdm_brett

Just keep it :) have it on your shelf! haha I got a 850 Con rod with a piston stuck to it as a candle holder.

and just too add 1098 and 998 Con rods are the same its just different piston gunen pin holes heights are a little bit different

Sorry to add. .. but a would throw them in the hedges. ..... not worth the risk,

For forced induction use as the engine doesn't. Use high RPMs

IMO use standard rods with ARP bolts
With lightened. Rods you may get 6" more over the quarter mile

Only really one way to find out.... Really depends on if you like engine building. Without FEA and CAD simulations the only way to find out is to try it. People told me that a std crank was only good for 150 bhp. I've been using the same star crank for over 10 years over 150 bhp, and now over 250 bhp. If something never breaks is it over engineered?

Team www.sheepspeed.com Racing

conrods make good car prizes




and used pistons are very useful as ashtrays in the workplace if you are a smoker

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

This is what the professional engine builders do for Mini 7s:

Edited by Paul S on 15th Sep, 2012.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Nice effort, but yeah- the small end takes a fair bit of stress when the piston gets to the top of the stroke it wants to carry on hurtling upwards, the rod has to hang on to it and pull it down. I recall hearing that a big % of conrod failures are because they stretch at the top of the stroke and let the piston make contact with the head/valves.

IMO weight off the small end is a good thing as it is purely changing direction (up-down-up etc) which takes a lot of energy to do. The big end is just rotating with the crank so there is only a constant directional change. I'd do them again but take less off, if you're happy to experiment with your engine that is.

Only my opinion of course!

TC

www.topcatcustom.co.uk

personally I'd give them a shot in a 998, but in a 1098 with the linger stroke I think it may be a bit risky.

10/10 for enginuity though, that jig has made a nice job of them.

[quote=Turbo This..,14th Sep, 2012]
im i right to think 95% of the forces on the small end are pushing down the beam so its quite safe to go this thin on top? is it only the weight of the piston getting puled down ie drag from the rings and piston that will have an effect on the rod as boost while the intake is open will be pushing the piston down on the intake stroke well most of it?
/quote]

The forces at TDC are the highest .

for a 3.2 stroke and 8k rpm:
Maximum TDC Rod Tension GForce= 3720,62 G's
Maximum BDC Rod Compression GForce= 2099,97 G's

Pretty serious loadings. and the 1100 used an even longer stroke so ..

What material is that rod made of ? they downgraded the material a few times as the rod was bulky enough to get away with it. So if it is an early rod it might work... I would have clenched buttock syndrome all the time, so not for me. IF it lets go, the engine is trash. Can you, and are you willing to afford it ?

I´d say : why do this machining in the first place ( i like the method btw !), for a turbo you don´t need it and for a super high rpm engine i would not trust it.

Edited by Sir Yun on 15th Sep, 2012.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Stick em in a donor scrap block and run it up on a test rig. And stay well back. Maybe behind a blast shield. Good effort though!

What i learned school is:
What kills a conrod is when you close the butterflyvalve. The conrod can take a massive beating at full throtle, but when you close the butterfly, you create a vacuum above the piston, making the rod break.
I have made several sets lighter with the help of the yellow bible from uncle David. i took out approx 120 gram.(No idea what it is in pounds)

It did take a lot of time and today i wouldn´t do it.

P.S. They did hold in a overbored 1098 @ +7500 rpm.

If i have more toys than you when i die, I WIN

what do the rods weigh as standard? mine are down to 499g each (1275 A+) but my little end is only lightened enough to remove the casting marks then a good polish

Attachments:

1.06mb

Yes i moved to the darkside

Instagram @jdm_brett

i do have two spare blocks so i could run them up to speed it would be a bit of messing around as i dont have all the parts to put in the firing line but worth it i think

i have started a different set ive taken just enough off it this time to get a constant radius well 6 different angles really but once i ran the flap wheel over it its blended nicely

this is where im wel ill go do some work on one and take some pics so far i plan to finish the small ends and polish them all up then take them to have the big ends spun then ill finish polish them like brett has

think a stock rod is 660g ? or is that a 1275? my scales are on there way

Brett how did you polish them up that well?!

www.topcatcustom.co.uk