Poly Urethane or Stiff Rubber Motor Mounts

[Mike]

Have any of you ever used a polyurethane motor mount for your ATV? I am getting a lot of flex from the mounts in Jennifer's mid-engine Max IV and since I do not know the shear properties of the stock rubber vibration isolators that I am currently using from Recreatives Industries, I was hoping switching to a poly isolator would be an easy way to stiffen things up. I haven't had any luck finding a poly mount that is the same size though, or at least something close to the same size as our stock mounts?

The other option would be to find the stiffest rubber mount I could. Got any suggestions or even better, links?

This place had a ton of cylindrical vibration mounts: Square Cylindrical Vibration Mounts Rubber Neoprene Urethane Sorbothane Silicone Gel Ring Mounts Stud Nut Type but I really don't have any base properties of the stock max mount to compare them to.

[George]

I've heard of guys using hockey pucks to lift trucks and such. Perhaps you could make something using those.

[Mike]

I thought about just taking a piece or round plastic stock and throwing it on the lathe, but I was worried that it would be too stiff and I would end up with a lot of vibration that I could feel in the seat. It may not really matter though.

[hydromike]

Since we don't have the engineering qualities of the original Max units to compare to, a direct comparison is impossible for now (unless we uncover their vendor! {insert evil laugh}). I think that most of the units encompassed by this link are natural rubber, but their properties may vary. Have you considered going with solid mounts? Just as a baseline to see if you completely detest the ride quality?

Vibration Isolators

One of the higher shear strengths on this unit. Doesn't mean it won't flex, but it means it *should* hold up....

beefy

~m

[racerone3]

Beth's max II is the only machine in our fleet that has any rubber between the engine and frame. in all of the machines that i've done engine swaps (or rebuilt the mount in the case of the hustler) i've eliminated the rubber. not to say that there is no difference, but if there is a difference i sure can't feel it. in her max, when i rev the engine i can see it twist slightly in the frame as the clutches ramp up... it looks to me like the clutches get pulled out of alignment slightly when it does this. not saying either way is better, just some things to think about

[Mike]

Thanks everyone, that was exactly the kind of input I needed. I think I will try one of the higher strength rubber isolators like you linked to Mike and then if I still get too much flex I will eliminate it by going with a hard plastic or even metal mount. I have to have something to raise the motor stand up above the sprockets otherwise I could just mount the motor stand directly to the frame.

I found some poly mounts on that first site I linked to but their shear rating was much less than some of the rubber ones.

Brian, after hearing your comment about not using any isolators at all that makes me a little more comfortable with doing that if I have to.

Thanks again.

[lewis]

Mike the durometer reading is how soft or hard a product is. Mcmaster-Carr is a very good source for machine vibration mounts.
McMaster-Carr the bottom of the page there is a two piece vibration isolator. I has a very significant axial and radial load capacity. I used a two piece on the crush and torqued them down equally and they seem to work well. They have a center line bolt that is removable.

[6X6]

Hi Mike:
I'm talking with Mogman (Jimmy) about this, and he's thinking what I am. Poly isolators are stiffer and will not wear out as fast (get too soft) Poly-urethane is more desirable in automotive use, but if I redo the isolators in any of my machines, I would personally favor Poly over rubber. As for the shear strength, like Lewis said, that doesn't directly state how hard they are. I used to have a durometer when I raced R/C on-road for testing and matching Foam tires ( Yea, I was TOO into it), and that is the true hardness test.

(Edit) Both me and Jimmy would personally use a Poly isolator to remove the flex without hard-mounting. If you talk to any Hot-rodder or Muscle-car guy they'll tell you they went to poly bushing in their suspension to remove play and sway, and these machines aren't going to produce the stress to shear an appropriately sized/rated Poly mount.

[mad_max_500cc]

mike have you seen the aluminum and rubber mount setup that ri uses on the higher hp motors? i have them on my max and seem alot more solid than the rubber ones ill snap a Pict when i pull the engine out (maybe this weekend )

[jpswift1]

mike have you seen the aluminum and rubber mount setup that ri uses on the higher hp motors? i have them on my max and seem alot more solid than the rubber ones ill snap a Pict when i pull the engine out (maybe this weekend )

Eric is right on about this. Those aluminum motor mounts with the hard rubber vulcanized onto them work great. I'd be more than happy to pick some up for you the next time I go to RI.

[jeffery9076]

beefy

I use the beefy ones or something like hydromike showed the link for that came with industrial size blowers for shipping purposes they just throw them away. Bruiser still pitches the engine forward some during rev up. I was thinking of polyurethane mounts some type of body lift for vehicles. I might be going to work for my previous employer for winter.. I hope Then i will have access to drill presses ,lathes. plastic welders. plastic formers, I need to get a piece of abs and get some abs flange rings made for the outside bearings

[Tango42]

I changed over my superchief to urethane last year. They stiffened things up and didnt cause a noticable increase in vibration. I got them from here: MISUMI USA, Inc.. It still wasnt stiff enough for me.....so I built a torque stop to mount near the clutch. Its basically a plate with a urethane bumper that limits how far the motor can pull towards the transmission to keep the clutch center to center distance more constant.

[hydromike]

so I built a torque stop to mount near the clutch.

maybe that's the answer. Keep the rubber bushings/ isolators for minimizing vibration, but keep a torque limiter on it to stop the torsion aspect. Vibration is pretty much a static back and forth (that's a total contradiction, I know...) but trying to eliminate torsion is a whole different ball game. Is that an option on the Max IV, Mike?

~m

[Roger S]

I like rubber, although argo doesn't use them. Decades ago, auto engineers redesigned rubber engine mounts so if the rubber sheered, the mount had steel fabrication that limited travel even with broken rubber. that's what I'd be looking for. Poly likes to get loose, esp in suspension.

[Mike]

maybe that's the answer. Keep the rubber bushings/ isolators for minimizing vibration, but keep a torque limiter on it to stop the torsion aspect. Vibration is pretty much a static back and forth (that's a total contradiction, I know...) but trying to eliminate torsion is a whole different ball game. Is that an option on the Max IV, Mike?

~m

Yeah, I already have one on the rear, clutch side of the motor stand to prevent it from moving too far back. Max II's come with something similar from the factory. I think I ended up using a freeze plug for my stop.

Thanks for all of the suggestions and links.

I only have excessive movement when I get the Max IV under an extreme load like climbing a really steep hill or a large tree. Then I can feel the plate shaking back and forth and it starts to oscillate more and more unless I let off the throttle. You can kinda see it happening in this video. Fast forward to 1:00 in the video when I am trying to climb that fallen tree: