Burtz vibrations

The balance weights for any in-line or single cylinder engine are never 100% correct because the piston goes up and down and the big end of the rod goes in a circle. However, there is a way to get the weight of the piston, rings, piston pin, and small end of the rod balanced so that now all the weight is concentrated at the big end of the rod. It is not a practical solution. Theoretically possible but no engine manufacturer would ever do it. A 90 degree V configuration could be near 100% balanced.
 
I have been down this road myself.

Let me preface all this by saying that I really enjoy my burtz engine. I've built two, and I would recommend one to anyone. I wouldn't hesitate to purchase another for myself if I had need.

My car is a 31 slant window. It has a burtz engine with a burtz cam, burtz high compression head, and burtz flywheel. Mitchell tansmission & overdrive. New bob drake universal. 4.10 rear end.

Initially I did not have the float-a-motor mounts, and the vibration was significant. Some all the time, but not to a concerning level when accelerating/pulling. (As a side note, I feel in my case this vibration was amplified due to the fact that my car is all steel, with no wood to help absorb anything.) But during any holdback and especially between 2000-2300 rpm it was enough to be very concerning. I initially thought something was majorly wrong. I asked on facebook, Ford Barn, and VFF. I checked everything suggested. I even had several conversations with Terry. I was coming off a complete, frame off rebuild of my car so absolutely everything had been gone through. I dutifully double checked everything but could find no issues anywhere. With nothing to lose, I went ahead and installed the float-a-motor mounts and found they helped dramatically.

At this point, I've accepted the vibration is just a harmoincs thing that these engines do. With my engine, I find the vibration only occurs when holding back going downhill, and only between 2000-2300 rpm. Below and above that range, the engine is smooth. When accelerating or pulling a hill it's very smooth with no vibration at any rpm - I've had it up to about 3000.

I built a second engine that went in a 29 phaeton. Burtz cam, burtz high compression head, original flywheel, mitchell transmission, 3.78 rear end. I did put in float-a-motor mounts right off the bat. I completely rebuilt this car as well, and it has exactly the same vibration in the same rpm range.

For those who say they never experience any vibration with their burtz engines, I am curious to ask: do you have the roads to get your car in the range where in my experience they vibrate? That is, only during holdback in the 2000-2300 rpm range?

~Ernie
 
Jeff/Illinois said:
'How the heck do they balance the new THREE cylinder engines:eek: And how does a four stroke engine work with three cylinders?
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I recently bought one. I had no idea a three cylinder existed, but sure enough...it does. There's no notable difference between it and any other car. Pretty wild. Oh, for the kind of car (small SUV) it gets really fantastic gas mileage. :cool:

ErnieF said:
For those who say they never experience any vibration with their burtz engines, I am curious to ask: do you have the roads to get your car in the range where in my experience they vibrate? That is, only during holdback in the 2000-2300 rpm range?
Click to expand...

I'm curious to see the answers. I have a Burtz engine (block, head, and flywheel) that I plan on installing shortly. I thought about going for float a motor mounts, but I'm trying to maintain the stock look as much as possible. If I need to do float a motor mounts...might as well do it while the engine is out and I'm cleaning up that part of the car anyway.

Curious as to others' experiences.
 
Lawrie said:
My A had the some vib on overrun through using 3 engines, the last was the current Burtz eng,I took out the original box type rear mounts that were both cracked, I didn’t like the floats motor ones, so made my own using a V8 engine Mount, it’s now the smoothest it’s ever been.
Lawrie
Click to expand...

Still waiting for pictures !
 
Manufacturers today have resorted to hanging weights on the frame and transmission to dampen the vibrations.
 

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I agree with Synchro909. When I built my engine I installed a rebuilt u-joint which noticeably reduced vibration on deceleration. It seems the amplitude of vibration is most noticeable upon deceleration. My guess is if the u-joint is worn the axial torsional load when decelerating is lower which allows for more oscillation to occur than during acceleration. The vibration is then transmitted through the drive train giving the impression the engine is imbalanced.
 
Sorry guys ,pics welcome, I will look them out.
But as I said in my post, my A had this over run vibes for years and various engines,it was the cracked original mounts, so after making my own to utilise the V8 mounts its now very nice and the vib has gone, done heaps of miles.
if you want my unsanitized drawings let me know.
My mounts were only made of the 12mm plate as thats what I had, they could be made a bit different if you want to remove the lip on the flywheel housing.
Lawrie
 

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Hi Lawrie, and thanks for the pics. Well done on the mounts. I'd be interested in seeing your drawings as I'm about to do a similar mounting. Also, do you remember how thick the wood is where the cowl bolts down to the frame? Mine is long ago rotted away of course.


Terry
 
Hi Laurie, could those V8 rubber mounts replace the hockey pucks that come with the float o motors? Thanks for posting the pictures. I have found a way to improve the floaters if anyone is interested.
 
The floaters depend on the rubber being able to flex. The bolts should only be tightened enough so that they are not loose and maybe a little more.
 
I am a long time user of float o motor mounts. There is a direct path for vibration through the bolt to the frame mounting bracket. I added a 1/8" thick rubber washer and fender washers top and bottom which requires a slightly longer bolt⁷ which interrupts that path. It does make a difference. I have a photo of the package for the washers I used but do not see how to post it.
 
Richard,it sounds like you must be missing some parts.On the top you have a metal cup,under that a rubber puck.On the bottom,or nut side,there is a metal cup,and a rubber puck on top of that.There is no metal to metal contact between the bolt and the frame mount.I did take one apart that had a shorter bolt,and no cup or puck on the bottom.The nut was tightened right up against the bottom of the frame mount.
 
Kieth, trust me I have all the parts. When assembled the nut on the bottom contacts the frame motor mount bracket. That is a metal to metal contact area. Inserting the 1/8" rubber washer in that area eliminates that metal to metal contact. I did the same on the top because I can. The duremeter of the hockey pucks is a mystery. Motor mounts insulate best when they are in shear. Adjusting the bolts is an art. Unequal tightness is a thing. I probably installed my first set of floaters back in the 70s so I have some time to think about this.
 
That's interesting.I have three rubbers on each side.The bottom one,UNDER the frame mount,is a D shape to miss the frame rail.The washer that the nut rides on is a D shape also.These are on my A that my uncle parked in 1954.I've installed quite a few sets over the years,and now that I am thinking about it,I don't remember the D shaped parts on them.Maybe that's just on my old ones.In theory,without any pad under the nut,there is no engine metal to metal contact with the frame rail.BUT,it seems like quite a few of the rubber parts were as hard as a real hockey puck,and you might as well use a steel pad as to use them.I have three other A's with floaters,I'll go have a look at them.
 
It is true that the rubber gets hard after a while. It needs to be replaced when it gets hard. Same is true for the rubber pads that go between the mounts and the frame, on both sides. Even with the Float-a-Motor mounts the rubber pads against the frame get hard and need to be replaced. I replaced the ones on car that must have been 94 years old. They had no flexibility left. These are the original vibration absorbers for the original mounts. They work in conjunction with the Float-a-Motor mounts.
 
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Kieth, that's very interesting. If I understand correctly the very old floaters actually have that extra pad on the bottom. So is it possible in the original design the D pads and D washers were included and at some point when these floaters were reproduced someone decided you don't need that extra pad and washer. I find it very interesting that I came to the conclusion of needing that one more pad when the floaters might have used that design in original form. I added that extra pad and washer a couple of months ago and I did notice a difference.
 
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