Centaurus

[Ih8Suvs]

To anyone having experience with the Centaurus Enfields, I hear that some people are having problems with the frames cracking. Does anyone have any insight into where they are cracking. I ask as I have a Ruggerini MD151 that I am planning on installing in an Enfield. This is a similar (Centaurus used a MD191) engine and I would like to solve any frame weakness problems before they occur.


Tim

[oilburner]

It might be worth investigating the use of Lovejoy or similar anti vibration mounts when mounting the engine in your frame. You could add the mount attachment points onto the engine mounting plate and onto the head steady.

FWIW
Avery

[oldbmw]

IT might be worthwhile looking at a post 1962 big twin Enfields, later the better. these frames had to be beefed up for teh bigger engines 700-750cc.

Or... maybe hichcocks have a twin frame for sale??

[Ih8Suvs]

All good suggestions, however what I really want to know is where on the commercial built Centaurus the frame is cracking so I can beef up or redesign the frame or engine mounts of the bike I already own.

[Stuart]

I think someone said that that particular engine didn't lend itself to bikes in that its internal config would cause too much vibration - on top of it being diesel.

[Ih8Suvs]

I think someone said that that particular engine didn't lend itself to bikes in that its internal config would cause too much vibration - on top of it being diesel.

Well I find that curious as the MD191 seems to have been successfully used in the Ruggfield, in various MZ, Dnepr, Ural, Moto Guzzi, and BMW conversions, other engines of the same configuration (two cylinder inline staggered crank) ie the RD211 or Hatz 2G40 have been used in various other bikes. Doesn't Sam Brumby's Yamaha and Dave's (Locomotive Breath) Honda have a RD211? Also, what would it be with that configuration that would cause vibration. I know from running it that my Hatz 2G40 is very smooth running. Why would a MD series engine be more prone to vibration? Perhaps while my MD151 is apart on the bench I should take the rotating/reciprocating mass to the speed shop for balancing.

At any rate what I really want to know that no-one has answered yet is *where* the frame on the Centaurus is breaking. I hear anecdotal reports of frame breaks but no-one says *where* they are breaking. Is it random? Or is it one particular area that tends to crack? Is it the frame itself or the mounting system used on the Centaurus that is breaking?

Thanks, any help addressing the specific question would be much appreciated. We could certainly start a new thread concerning why a MD/25LD series engines are unsuitable and if/how *that* is correctable.

[sbrumby]

Sorry cant help with the Enfield question, basically fairly low hp bike designed a long time ago. Single downtube, so if you replace petrol with low hp diesel usually no problem. If you replace with beefier hp diesel with vibration you are probably outside what the frame can take. So then you need to weld on a bit of extra help. As for the ruggerini engines I cannot find the reason for the two differences ie MD & RD, both mine are RD engines, I have seen German bikes with MD engines where the starter motor is at the front, RD have this at the back. I pressume the MD is a 180deg config same as RD, what this does is gives power stoke followed by another one then nothing for quite some time. This makes the engine sound like a Harley but is tough on vibration and primary chains. Any reason why you need to use the Enfield? I know you have one with gearbox, but secondhand Jap bikes are cheap and you get disk brakes tubeless tyres decent suspension, you can still use the enfield gearbox.

[oilburner]

I may be able to help you determine the differences between the MD and RD series Ruggerini engines.

For one thing, the RD series has one injector pump with two plungers.The MD series has two separate Bosch PF30 injection pumps.

To determine the other differences you can download the workshop manuals for both series at the following link and compare them:

http://service.ruggerini.it/italiano/man_index_i.htm

FYI

Avery

[Ih8Suvs]

Yes I have the service manuals and am somewhat familiar with both series engines, that is why I questioned why an MD series would vibrate more than an RD. They both have the same cylinder config and firing order, ie staggered crank for balanced reciprocating mass and odd firing order.

But seriously guys what I really really really really really really really really want to know, all speculation aside about why, is WHERE WHERE WHERE the frames are breaking.

[oilburner]

The rumoured problem areas of the frame are probably at the welds - if the tubes themselves are breaking, some serious modifications would be in order in which case IMHO it would make more sense to select a different donor bike if frame surgery is not an option. Otherwise, I'd accept a small weight penalty and gusset the frame at every joint to mitigate any potential problems. The /5 series BMWs with a sidecar were known to break the frame under the gas tank. Gussetting solved the problem. A good reference for proper gusset technique and frame building is Motorcycle Handling and Chassis Design by Tony Foale.

Avery[/i]

[andrewaust]

Hi Ih8Suvs


The bikes I've personally owned that have suffered from frame fractures have gone from the headstock "Steering Area" of the frame.

Now this was not from vibration, rather stress forces from racing. Surprising enough the last was a Kawasaki Motocross bike with the new type of perimeter frame.

Now I know this doesn't really answer your question, but from a view point, the headstock is one of the most likely places to go. I notice my Enfield has gussets in this area, good welds and a rather robust construction and until now, no cracks - although I constructed a full lower cradle to fit the Diesel in, not letting any part of the engine be part of the frame support.




Cheers


Andrew

[Ih8Suvs]

If the headstock welds are breaking this could be easily beefed up with some creative gusseting.

On the stock Enfield the engine case is a stressed member of the frame carrying the load of the front down tube to the rear. On my yanclone Enfield, I, like Andy, used a cradle so the engine case is not a stressed member. It sure looks like Jochen Sommer is using the Hatz engine as a stressed member however. Jochen is a good engineer though, and I am sure he has the bracing right. I wonder if he beefs up the frames anywhere else.

I just wonder if the Centaurus builders didn't exactly pull the geometry off correctly. They are using the engine as a stressed member, but if engine vibration puts stress on the headset welds, or the engine doesn't properly transfer the load of the front downtube to the rear of the frame this could be the reason for the failures. That is why I would like to confirm where they are breaking. Is it indeed the headset? Most likely I suppose. Also the most sinister to have happen while riding.

Has anyone heard of a Ruggfield style conversion failing?

I am going to get the book you suggested Avery. Thanks for the reference.

Tim

[oilburner]

Hmmm, this is probably a stupid question, but have you attempted to email/contact the fellows who built the Centaurus? Maybe they would be willing to share some information. The problem must have been quite serious with no easy fix for them to discontinue production. BTW I agree the Centaurus is one great looking bike - it would be good to resolve the problem whatever it is.

I wonder if the staggered crank *across* the frame is somehow contributing to the problem. My non scientific analysis suggests there would be a rocking couple that could be sending undesirable vibration frequencies up the single downtube.

Another approach would be to "jack up the serial number" and put a complete new Enfield inspired robust frame under it, made of DOM tubing with a sufficiently thick wall that would not only offer increased strength but also reduce or eliminate sympathetic vibrations by moving the frame's harmonic frequency away from those of the engine. As I stated in a post several months ago, this is what Indian did with one of their four cylinder bikes to resolve a vibration problem (ref. Indian Four Motorcycles by Jerry Hatfield)

Avery

[oldbmw]

I heard this from one of the builders at the german rally.

The centaurs ran fine, it was at tickover speeds that vibration caused frame cracks, I think in teh headstock area.
I wrote in a previous post i beleive the answer is to extend teh backbone of the frame and not shorten the downtube. By shortening the down tube the headstock gets stressed further by the engine. I would look to scarf in two down tubes and loop under teh engine to connect again in teh area of the swinging arm spindle. you may lose a little ground clearance. which wont normally affect cornering unless you on a very bad surface. when extending the backbone beef up the entire area. Using this approach you will have room for teh five speed box with the hatz IB40 engine.

[Ih8Suvs]

Avery, the rocking couple idea is something I hadn't thought about. That could certainly set up a side to side vibration. I have to think about this some more. oldbmw, interesting. I could. I think, put this engine in without shortening the down tube by eliminating the electric starter. I don't know how brutal this thing would be to kick start though. It is only a 654cc motor. The 406cc Yanmar clone I am running now is dead easy to kick start so that might be something to look at too. Your idea of two down tubes is also a good one. I think that could also stabilize the rocking couple vibration that Avery brought up. What do you think of replacing the single downtube with a double brought out around the starter and then continuing under the engine to the rear frame? I think I could make it all fit without lengthening the backbone that way too and keep the electric starter. Your idea, Avery, about using rubber mounts merits further investigation also. Interesting that the cracks are happening at low rpm's. I need to run this engine on a test stand and get an idea first hand on how and at what RPM's it shakes. It is entirely possible that I will have no problems as this is the smaller MD series engine and not the 851cc used in the Centaurus. Identical configuration, just smaller.
I had thought about using my 2G40 in an Enfield, but had decided it was just too big and heavy. This 654cc MD is quite a nice small and light package. Considerably smaller than the 2G40.

Tim

[Anorak_ian]

Hi, just a thought, but if the problem happens at tick over, it may be a good idea to lower the revs from 1000 to around 800rpm, this may take away some bad vibes.

[oilburner]

If you want to scare youself silly, build or borrow a strobe light and shine it on the engine. This should show the engine vibration characteristics. If the engine is installed in a bike, it should show any sympathetic vibrations in the frame. A friend has a strobe and has offered to use it on my bike when I finally get it finished, but to tell the truth it might frighten me so much I'd never ride it!

On a related note, I agree with oldbmw about twin downtubes. Two tubes should significantly stiffen things up and reduce side to side oscillation tendencies. I suspect though, stiff is good up to a point. If the frame is too stiff in a certain area, the result might well be to move unwanted vibrations to another area of the frame. Looking at pictures of the Centaurus, it appears the single downtube morphs into two about halfway down, probably due to the modifications for the diesel engine? Perhaps the two tubes or whatever they are could continue up to the steering head with a re-work of the attachment there. That would allow you to retain the electric start and a conventional frame layout.

Avery

[sbrumby]

Many thanks to Avery for the link to the ruggerini workshop manuels.
I have a couple of questions, why do they produce both MD & RD engines?
Both engines are 180deg type, I thing the old Triumph twins were 360deg type which I would think was a lot smoother running than 180deg, what is the advantage of 180deg?

[oldbmw]

Many thanks to Avery for the link to the ruggerini workshop manuels.
I have a couple of questions, why do they produce both MD & RD engines?
Both engines are 180deg type, I thing the old Triumph twins were 360deg type which I would think was a lot smoother running than 180deg, what is the advantage of 180deg?

You are right, the old Triumphs were 360 degree engines. These have an even firing order, but as both pistons ( and conrods) move together they represent a considerable weight to balance. Unfortunately, you can only balance a reciprocating weight with a rotating mass at one specific speed (rpm). The 180 degree layout gives much better natural balance because one half is going down when the other up, so equalise ( if you forget the rocking effect of teh offset cylinders) Some modern bikes ( triumph speedster ) for example have a 270 degree crank. To make it fire uneven and sound like a harley ???
Problem with the 180 degree engines is they oscillate as they have two firing power pulses at 180 dgrees apart then nothing for 540 degrees. This is ok for water pumps and saws, gives uneven phases when used as an alternator. induces drivetrain rattle... ( some say it can make you sea sick ? )

[richard coles]

hi, just thought i'd mention that a 270 degree crank is the same as saying 90 degree (as a circle has 360 degrees).
So the sound would be more like a ducati

[oilburner]

Hmmm. I'm not so sure about that. I Googled 90 vs 270 degree cranks and from the discussions there is a difference.

For one example, check out the explanation here:

http://www.sense.net/~blaine/270.html#9 ... t%20timing

Avery

[oldbmw]

Hmmm. I'm not so sure about that. I Googled 90 vs 270 degree cranks and from the discussions there is a difference.

For one example, check out the explanation here:

http://www.sense.net/~blaine/270.html#9 ... t%20timing

Avery

This is exactly correct. at very high rpms 9 say above 8000) you dont notice so much, but at tickover it is very pronounced.

[Heiko]

look here
http://www.enfield-wiki.de/index.php/Vi ... _Centaurus
if you make that you will have no problems with vibrations wich kill your frame.
you can go full gas not only 80kmh.
heiko

[Stuart]

I've tried to do a rough translation of the article into English. Please excuse my efforts (they were aided by web based lanuage tools that weren't very good )

Many thanks to Heiko for pointing it out.

Vibration killer Centaurus

Hi I have recently bought a Centaurus.

I bought this it in a poor condition. On the first test ride I went to about 1 km and the cable harness went up in smoke. I Built a new cable harness with glow starting switch, everything soldered with heat shrink sleeves and clever cross sections divided at the same time. With the Centaurus nearly completed I fitted and painted chrome shields and single seats having driven it only once.
It does 120kmh and more, but the vibrations started from 80 kmh and are intolerable therefore the framing breaks, though a the predecessor warned me in this already.
I did not drive it so fast so I screwed a sidecar type globe to the centaurus.
It looks super, but the vibrations through the steering wheel rubber mounts meant a larger support plate is wanted.
Then I thought of the engine was not balanced so I unscrewed the cover of the flywheel away and installed it into the existing M8 thread screwed with different weights to sometime thought I for having the correct weight and took a piece metal and screwed it to places now makes it correctly for fun can it fully turn off let almost vibration-free!!.
Vibrated is now less than my 500er bullet, only to the comparison runs with sidecar approx. 110 kmh, with woman and child still 100. At the clutch I have also out of print if I mean myself other Diesels with sidecar or bullet, I sold the trockenkupplung (?) to buy to gel battery have I me now also ordered then could all teething troubles be eliminated, think I am now with family 500km we am driven all enthusiastically and without incidents and vibration-free super.

[Ih8Suvs]

Thanks Heiko for the link, and also Stuart for the translation. I had stumbled across that before but had forgotton about it. What it looks like is he basically fabricated a counter-weight to attach to the flywheel. I am going to experiment with that when I get my engine started.
I bought my engine (MD151) used, it turns out it had barely been run, only long enough to faintly soot up the piston tops. I don't know exactly what the story is but I suspect since it was so low time ( would surprise me if it had run for more than 15 minutes) it was pulled for warranty reasons. When I got it it had no compression on #1 cylinder ( a small piece of metal swarf stuck to the intake valve which a simple lapping job took care of) and had excessive crank axial play. Turns out the cam gear which sets end float on the crank was improperly installed. Easy fix. But it came without a starter which I have on order. I am anxious to get it running and see how much vibration it actually has. The MD 151 might be a whole different beast than the 191 as far as vibration goes. Physical size wise it looks ideal for the Enfield, and the 16.3 hp should provide noticeably better performance than the 10hp Yanclone I am running now.

Tim

[oilburner]

I wonder if there might be an alternate and more accurate means of determining the weight and location of the counterweight to be added to the flywheel.

When you have an engine balanced, there are several balancing steps. The connecting rods are balanced and the pistons are balanced. The flywheel is balanced. The connecting rod and piston combination has both rotating and reciprocating mass. A pecentage of this rotating mass and reciprocating mass is bolted to each connecting rod journal on the crankshaft using devices called bob weights. The percentage value, known as the balance factor, depends on the RPM the engine is being balanced for. A racing engine uses a different balance factor (higher) than our 3600 rpm diesels would require. At one point, the flywheel is also bolted onto the crankshaft and the complete crankshaft / flywheel combo is balanced.

If you know of a balance shop, perhaps you could take everything there and explain what the problem is and ask if they can help. Perhaps they might be able to do their magic on the flywheel so that an additional counterweight isn't necessary. At the very least, they should be able to tell you how much additional weight is required and where it should be placed.

Engine balancing is not that expensive, in 2001 I paid $200 to balance a 1000cc BMW engine. I believe it's cheaper elsewhere. The engine was glass smooth at 5000+ rpm. In the case of the Centaurus, it should be well worth the cost. perhaps the original manufacturer of the Centaurus would be inspired to resume production if the vibration problem could be resolved.

If you Google *engine balancing* you will find lots of info on this "black art".

FWIW

Avery

[oilburner]

Another idea. If you have a strobe light, can make one or can figure out how to trigger an automotive timing light, you could use it to watch the vibration and accurately pinpoint where to add the weight. By trial and error you could add weight until the light no longer shows vibration.

FWIW (2)

Avery

[Ih8Suvs]

I will use the strobe light idea. If this think is a buzzy engine when I first run it I will tear it down completely and balance it. If it still buzzes then I will explore a counter weight on the flywheel. I considered doing it right away, but seems it would make more sense to see if I have a problem first before fixing it. Course a good balance job never hurt anything anyway except the wallet.

Anyway, still waitin on the starter. S'posed to be here the 11th.

Tim

[henneberg]

Hi Tim,

I know this is an old post , but did you succeed implanting the MD151 into the Enfield frame

regards, Erik