Plain Bearing Conversion....Ideas?

[dsmess]

I was wondering if anyone has done this to a Ducati single. The last evolution of the bevel twins...the Mille featured plain rod bearings. Kevin Bracken also converted an earlier V-twin. I've seen many singles with early rod bearing failures. The engine is so overbuilt and robust in the other areas (except maybe the narrow case leaf spring for the kick starter). I know....keep the revs up, change oil at 1000 mile intervals.

Thoughts about ways to change to a plain bearing at the rod anyone?

Scott

[DewCatTea-Bob]

____ Plain-bearings for the con.rod's big-end? _ Never seriously considered by me...
First, you'd need to come-up with a stronger oil-pump to produce the required oil-pressure that normal plain-bearings are meant to work with !

____ I'd be more interested in alternate bearing choices to replace Ducati's stock set-up. _ Such as either using a greater number smaller roller-bearings along with a crank-pin which has a larger O.D., or, larger roller-bearings along with a smaller crank-pin O.D.
__ I've had narrow-case crankshafts torn-down and found them to have twice as many rollers without a cage !
I'd really like to know which is more common in the DUKE-motor cranks,, that 40-roller set-up, or the set-up with half as many rollers included within a cage !? - (I really haven't had very many crankshafts torn-down.)
__ Back in the '70s, I heard of super-hard alloy bearings which were Teflon-impregnated, made-to-order for most cycle-motors. _ I never ordered any of those but, I did order their Teflon-impregnated alloy forged-pistons for my 250 & 350 projects back then.
I wonder why such Teflon-impregnated parts didn't catch-on as a common practice since those days !? _ Cuz my motors worked quite well with those special pistons !
__ I have considered the use of two-piece con.rods for special-projects (requiring different rod lengths), which I've wanted to try with an altered DUKE-motor. _ I had considered using such rods along with a std.roller-bearing -(bearing with inner & outer races), with an I.D. to match the crank-pin's O.D., plus with an O.D. to match that of the chosen rod's I.D. _ But actually finding such a std.bearing & rod combo to meet my needs was too big of a chore !
I wonder why such set-ups are not standard on many 4-stoke engines !? _ If it could be because of the extra weight of the added outer race, then it seems that could be made-up-for by using a lighter crank-pin and/or con.rod.

____ I'd really like to read any comments on any of this stuff above, (especially by advanced guys like Eldert !).


Fantasiful-Cheers,
-Bob

[Eldert]

plain bearing conversion

i have a German magazine with a article about someones conversion to a plain bigend bearing
it involves a awfull lot of work . the guy build a couple of 450 s
first of all you need a differend oil pump and a full flow oil filter . the oil must be very clean for a
plain bigend . furthermore there is so little room between the gearbox and the crank you cant use a 2 piece rod
and the engine was not pretty looking with external oil lines al over

i would stay away from it

i am using al kinds of of the shelf rods in my engines : Yamaha XT 600 ( 135.5 mm c.t.c. ) old Honda XL 500
( 141 mm c.t.c. Prox brand ) for the narrowcase engines i could not find anything close so i had Arrow precision make me some rods . i had them made for a KTM 32 / 40 / 20 mm bigendbearing ( longer rollers and more of them ) and run the rod without side ( thrust ) washers .modern Yamahas dont use side washers anymore .
if everything is square there is no sideload on the rod

Eldert

[miken5678]

out of curiosity what is an aprox cost for a rod through arrow? Lacey eng has them with the bottom crank piece for 510 pounds if i remember correctly. Not sure if it would be cheaper to go through them directly considering shipping and vat etc. wonder if anyone with a limitless pocket book has gone with ti. Did you end up going with alum without worries of rod stretch or did you go with a steel one.. also i or h beam?

regards

michael

plain bearing conversion

i have a German magazine with a article about someones conversion to a plain bigend bearing
it involves a awfull lot of work . the guy build a couple of 450 s
first of all you need a differend oil pump and a full flow oil filter . the oil must be very clean for a
plain bigend . furthermore there is so little room between the gearbox and the crank you cant use a 2 piece rod
and the engine was not pretty looking with external oil lines al over

i would stay away from it

i am using al kinds of of the shelf rods in my engines : Yamaha XT 600 ( 135.5 mm c.t.c. ) old Honda XL 500
( 141 mm c.t.c. Prox brand ) for the narrowcase engines i could not find anything close so i had Arrow precision make me some rods . i had them made for a KTM 32 / 40 / 20 mm bigendbearing ( longer rollers and more of them ) and run the rod without side ( thrust ) washers .modern Yamahas dont use side washers anymore .
if everything is square there is no sideload on the rod

Eldert

[Eldert]

Hi Michael

its al about the number of rods you order . one offs are very expensive.
the first time i ordered 4 rods . price was 430 euro for a rod . next time i ordered 8 rods price went down to 377.50 euro
if you order 20 rods or so then the price will drop more .
keep in mind you still have to make a bigendpin and buy a rodbearing

unless you wanno go into the parts biz and order 20 rods you better fork out the money to Mr Lacey
or Phil from roadandrace or maybe euro-rods

Eldert

[dsmess]

That's a good point about the 3rd gear to rod clearance. Looking at the wide case on my bench, I'm guessing about 1/4" clearance from the gear to the flywheel. The worst case I think is about 90 deg from TDC when the 2-piece rod bolts might interfere. One of the big attractions for the plain bearing rod is ease of maintenance with a 2-piece setup. I'm pondering the use of a 40mm crank pin drilled for proper lubrication. The crank is pressed together and aligned once & that's it. Triumph 650s and some Japanese auto engines use 40mm bearing rod inserts. I've seen some rods with the nuts facing the small end of the rod...this may solve the clearance problem. Installing a larger capacity pump able to handle high pressures in the same location as the OEM pump looks difficult. It may sound absurd, but I'm thinking of an electric oil pump with speed control and pressure regulator. I have a Guzzi pump and a few 12v motors lying about. I have no idea of the power needed, but would probably have to go with one of the new after market alternators. A safety mechanism would be needed to kill the ignition below a minimum oil pressure. The oil lines are not pretty, but necessary. The oil pump output would go to the timing cover into the RH crank bush. The strainer bolt could be drilled and tapped for the pump input line. The oil return line goes to the bushing elevating the dipstick & bolt. A smaller orifice in the oil passage going to the head would be needed because of the higher pressures.

OK.... I could be creating a monster.

Scott

[miken5678]

http://www.sip-scootershop.com/Products ... tails.aspx

i found this and for the prices if they include whats in the photo it looks like a steal.. however they dont look like a billet arrow rod

[Eldert]

Hi Michael
the dimensions are wrong on that rod .
i would not use Mazzucelli rods anyway . original Ducati rods have 2 oiling holes on top of the small end at the
10 and 2 o clock position . the mazzucelli rod has one oiling hole at the 12 o clock position
i seen many of those rods fail , they split open at the oiling hole

Eldert

[miken5678]

Hi Michael
the dimensions are wrong on that rod .
i would not use Mazzucelli rods anyway . original Ducati rods have 2 oiling holes on top of the small end at the
10 and 2 o clock position . the mazzucelli rod has one oiling hole at the 12 o clock position
i seen many of those rods fail , they split open at the oiling hole

Eldert

thanks for the heads up.. i was getting excited once compared to the arrow rods from lacey.. also considering the 12v nc conversion that they sell.. silly pound to usd conversion is very sad these days.