The technical adventures of Dr_C

Dr_C · May 22, 2015

Taffy said:
I convert everything to roller on the 650s so I throw these rings away. I'll send you one straight away and then at least you have it infront of you as an option.
Taffy

What rings are you talking about, Taffy? The rings I'm referring to are the inner rings of the roller bearing, with the shroud/edge that take a small axial load. Both times I have tried to use roller bearings, that edge has been damaged and pieces have gave large secondary damages. I have installed them with appr. 0,8mm axial play.

makazica said:
Mats, have you ever received a Nobels prize for your accomplishments in engineering? Have you worked for Husaberg or any other major (minor) motorcycle manufacturer? Would you donate a piece of your brain to me?

(To all) How come you choose Husaberg engines for your projects/experiments? Do you consider them superior, a good basis, easy to work on, inexpensive?

Yeah I know! No Nobel prize for me! What a scandal for the committee! I mean, the prize for having made the most mistakes, on one single engine type, should have been mine years ago!

I actually got a request from Husaberg back in 2005 for a billet cylinder head. They wanted to investigate if there was an advantage with moving the valves further away from the spark plug (!). I had by then tried to reposition the valves with larger diameter valve guides. As the castings had too little material at the location of the valve seats, they could not be repositioned without welding. The guides lost their press fit and welding the head made it soft and loosing press fit of the seats. I told Husaberg that the only way was to make a new castings or mill out a head completely. So I registered a company and presented them with an offer of a billet head, which apparently was too steep for them (2000€ for a complete head). Then they contacted a tuning company in Stockholm area to do the same welding exercise. I heard nothing from the result of that attempt...

Donating a piece of my brain? I fear scientists are standing in line already, but for much different reasons...

I choose Husaberg because of it being very light weight with high level of tuning from the start. And, Yes, patriotism naturally played a part! i mean, the original design was made by Mr Lars Nilsson at FOLAN, which was 12km from where I live. Lot's of skilled people withing motor design, tuning and manufacturing are clustered within a 40km radius, so that network is very valuable to me. Did I mention my machinists brother in law designs components for Koenigsegg, and my machinist manufactures them! Koenigseggs engine mechanic is doing my dynoing. My old neighbour used to be responsible for production line at Koenigsegg. I have welded som alu pipe work for the AC plumbing in a Koenigsegg, so I'm "surrounded"!

bushmechanic · May 22, 2015

he means an extra small thin collar tightened between the primary gear and the drive side ball bearing as used by dave clarke racing in the UK

#83 is a factory KTM crate engine NTN TMB ball bearing, while a roller is used on the other side of the crank

the new collar goes where #77 is currently and the seal #77 is replaced by another seal with a larger ID.

it stops the crank from moving axially unless the ball bearing moves in the case

Dr_C · May 22, 2015

Ok! The curve ball was expressing that the ring was "thrown away". I figured that there is nothing in an OEM engine to throw away!

I will put my engine together today with ball bearings, because then I now the replacement interval (5-6 hours). Any other bearing set up may have a longer or shorter replacement interval, but it is unknown at the moment. Since the consequences of a bearing break down are tough (lost race and maybe expensive secondary damages), this is not the time to experiment. I rather tear the engine apart after each race (1,5-2h), than exposing myself to the risk of a bearing break down.

After season (late September) I will consider making a new crank. It will be without CB with a thicker left cheek. The right side cheek will have two bearings. The extra one will be positioned in the flywheel compartment, mounted in a cage that replaces the flywheel cover. I'm not using the flywheel anyway so... Thats the easier way for my to make the mains last a little longer, but it doesn't make the big end any better. Then we are talking solid crank, billet cases, larger diameter primary gear and a split rod.

bushmechanic · May 23, 2015

yes please Dr_C !

and while we are making requests to the engine building factory Ill add a hayabusa gearbox to my personal edition

edit: what axial play are you running with the balls ? I would use 1.5mm

spanner · May 23, 2015

Hi Bushie,

F1 gearboxes run gears as thin as 5mm up to 12mm for the higher loaded low ratios, just need good materials. A lot lighter and compact that way.

Taffy · May 23, 2015

Taffy said:
Mats, are you using a ring on the crank to pull the crank to the left? you know, the ring is in the left cover and the nut tightens the gear onto the ring which is butted against the main bearing?

Taffy

it is a bit like this Mats:

this is the oil seal, with a 38mm ID and not the usual 30mm.

if your crank flexes, the ball, able to run 'free' in the middle of the trench, able to wollow and weave has it's best chance with this set up.

regards

Taffy

Dr_C · May 23, 2015

spanner said:
Hi Bushie,

F1 gearboxes run gears as thin as 5mm up to 12mm for the higher loaded low ratios, just need good materials. A lot lighter and compact that way.

Thumpers work with an uneven speed of rotation of the crank. This is very different from multi-cylinder engines, where there are far more acceleration pulses (from the combustion stroke) along 2 revolutions of the crank. This rough pulsation easily breaks the oil film between the teeth in the engaged pair of gears. If the oil film breaks, there is a great risk of pitting damages. Because of this, a thumper calls for much wider (and/or larger dia) gears than a multi-cylinder engine. It's all about the surface pressure in the thin contact line!

spanner · May 23, 2015

I think that the secret is in the material,
I read up about the gear drives in helicopters in testing they have
to be able to run dry for something like 20 hours without failure, the steel
used is something like $200 a kilo not like your regular $10 a kilo
case hardened steel found in the Husaberg box.

Dr_C · May 23, 2015

Ah! You are talking about Unobtainium!

spanner · May 23, 2015

It is obtainable but unaffordable.

Dr_C · May 23, 2015

bushmechanic said:
yes please Dr_C !

and while we are making requests to the engine building factory Ill add a hayabusa gearbox to my personal edition

edit: what axial play are you running with the balls ? I would use 1.5mm

Normally around 0,7-0,8 mm. Whats the deal with that large play? To cope with little and big end being out of parallel, and the crank not square with the bore?

bushmechanic · May 23, 2015

Hi Dr_C

no nothing that complicated ... making the axial play larger just provides more room for the crank to spread

since a large component of the load on the bearings is from axial crank spread this reduces the load on the bearings.

from my um er -- ejumicated measurements of forces required to re true an 80mm crank after it has spread under "normal use" this is in the region of 5-6 Ton at the center of the shaft.

if you were to have zero axial play for example then almost all of that axial force would be transmitted to the bearings.

if you increase the axial play the bearings have less work to do ... some of the axial force is instead able to be taken up by the crank and pin bending.

at some point this would lead to other issues possibly with the pin especailly if its tiny tack welded but Im again ejumi-guessing from watching my crank in the press that this happens at 3-4mm + of axial play ...

the DCR collar being mentioned i think will have no function at all with low axial play values since the crank will spread and reduce axial play to zero at quite low rpm pushing the crank axially into the both the main bearings with great force..

nice gearbox spanner .. I noticed the diameter of the gears is very large also reducing loads on them , ours are only at 60mm shaft centers which is very very tight compared to other similar HP applications and as Dr_C mentioned usually with multi cylinder engines. even with a knobby tyre you can see the dirt spray pulsing in time with the engine note on my 700

edit -- may need to increase big end axial play with larger crank axial play .. i found the factory spec of 0.5mm to be too tight for big end axial but this is with 0.8mm crank axial play instead of factory 0.5mm

Dr_C · May 24, 2015

Hi Bushie! I have never tried to translate the spread to real movement, but if the crank is spreading 1,0-1,5 mm at the bearing location - thats huge! But if imagining that crank in my lathe at 9000rpm, it would propably take the lathes 1000kg and jump around my workshop with it til the power cable was ripped off, so its comprehendable.

Ok. I'm off to my machinist to get these new cases milled out to be able to achieve that large play. Big end axial play is 0,65mm.

Dr_C · May 24, 2015

These cases I'm now getting race ready, offered no axial play at all with a crank 106,5 mm wide including bearings!

Taffy · May 24, 2015

we run 0.45mm big end axial float. you're going to have to fiond some space somewhere!

Taffy

Dr_C · May 24, 2015

Taffy said:
we run 0.45mm big end axial float. you're going to have to fiond some space somewhere!

Taffy

Yes. I had the bearing seats bored deeper on my other cases. I'll just have to do that again on this pair! [emoji4]

tourist · May 24, 2015

Out of curiosity, what cases are you using?

bushmechanic · May 24, 2015

Dr_C said:
Hi Bushie! I have never tried to translate the spread to real movement, but if the crank is spreading 1,0-1,5 mm at the bearing location - thats huge! But if imagining that crank in my lathe at 9000rpm, it would propably take the lathes 1000kg and jump around my workshop with it til the power cable was ripped off, so its comprehendable.

Ok. I'm off to my machinist to get these new cases milled out to be able to achieve that large play. Big end axial play is 0,65mm.

sounds good, ive been using 0.7 to 0.8mm axial play on the 35mm big end just as the RFS builders do. IIRC lineaweaver suggested 0.8 long ago for you on the 32mm pin

regarding the flex yes I agree it is quite impossible to believe such things occur down there between our toes !

but if the crank requires such a large axial force to become spread open to the degree they obviously do (we can measure the spread on engine disassembly) then we must justify it somehow other than jedi mind tricks

id love to see a slo mo film of the crank doing its little dance through a plastic window in the cases, then perhaps i could do more than guess what is going on

have you seen this picture of mine ? roller main bearing outer race PULLED 1.5mm inwards by the crank

if i had not made the retainer and seen it nearly broken off like that nobody could ever have convinced me the outer race of a roller bearing moves inwards at all let alone nearly twice as far as the axial play.

Interesting experiment i tried to retain the outer race of an Nj2206 with an alloy plate

you can see its cracked. the outer race of the bearing has been pulled
out of its bore by 1.5mm and with enough force to break the retainer.

I find this interesting as there is no easy way to apply a force to the outer race
in this direction. there is a lip but it can only push the bearing into its bore not
out

also I was running 0.8mm crank endfloat so for the outer race to move any
more than 0.8mm out of its bore means there is some extraordinary flexing
going on.

Taffy · May 24, 2015

Mats

you need to seperate 'flex' from 'expansion'. if you can let the crank grow to the right at no cost then the actual flex can be absorbed perhaps by the balls in theiir trenches?

you need a ball that will take flex and not have to worry about the expansion?

whenever I grab a ball bearing, there is no flex in them!

maybe you can get that by going for some special bearing?

Taffy

Dr_C · May 24, 2015

While waiting for machining of the cases, I amused myself with making a 3D-model of the existing crank. Then it´s easier to make the mods and wishes for a new design.

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