delrin bushings instead of rubber for motor mounts

teazer

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Delrin is not really a good substitute. I'd suggest finding rubber bushings from a another bike/source. For example, that part looks similar to say a CB175 sprocket bush or a TZ250 engine rubber mount.

Do you have the dimensions? Maybe someone can come up with an alternate part
 

Rimmy

Been Around the Block

irk miller

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You can use delrin over urethane, no problem. It's not an uncommon swap in automotive high performance suspension systems and off-road suspensions.
 

irk miller

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IMG_9148b.jpg
 

spotty

Vmax...why,yes i think i will
if you're going to make a bushing, use alloy instead of plastic, lasts for ever. I've got alloy ones in the Vmax and it makes the whole deal a lot stiffer compared to the crap factory rubber ones by locking the engine to the frame . you get more vibration though the bars and such but I doubt that'd be too much of a problem on a 350 or 360
 

cxman

Over 1,000 Posts
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talk to irk miller he is really good and up todate on casting urethanes he has made some parts for us before
 

Rimmy

Been Around the Block
Thanks for the replies. The reason I suggested Delrin was because I've seen it in a lot of motorsports stuff already (subaru parts, jeep parts etc). Plus, I could get 20mm OD stock and drill out the 8mm ID without having to go to a machine shop.


Spotty, do you suggest the alloy just because of the longevity?
 

irk miller

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Rimmy said:
Thanks for the replies. The reason I suggested Delrin was because I've seen it in a lot of motorsports stuff already (subaru parts, jeep parts etc). Plus, I could get 20mm OD stock and drill out the 8mm ID without having to go to a machine shop.


Spotty, do you suggest the alloy just because of the longevity?
I would go with Delrin. It has higher sheer strength than urethane, it self-lubricates and it has high chemical resistance. It is used in motorsports, which is why brought it up as well. Delrin would be an upgrade over the standard urethane.
 

spotty

Vmax...why,yes i think i will
Rimmy said:
Thanks for the replies. The reason I suggested Delrin was because I've seen it in a lot of motorsports stuff already (subaru parts, jeep parts etc). Plus, I could get 20mm OD stock and drill out the 8mm ID without having to go to a machine shop.


Spotty, do you suggest the alloy just because of the longevity?

both the longevity and the rigidity. with the stock rubber mounts in the Vmax it has enough torque to move the motor well over a centimetre in the frame under hard load. again i'm not thinking the 350 is likely to do that but extra rigidity never hurts (said the actress to the bishop)
 

Tim

Administrator
Staff member
Longevity shouldn't be a major concern. If the old rubber lasted a few decades, new rubber will last a few more decades. Just how many decades do you need this bushing to last? It's going to outlast the engine no matter what material you use.
 

irk miller

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I think the point was that the stock rubber is difficult to find or irreplaceable, so he was looking for an alternative he could buy or make. It's not that the rubber doesn't last long. Longevity is one of many benefits to delrin or alloy, regardless of how important it is.
 

Rimmy

Been Around the Block
Spotty and co. I should have made my question a bit clearer. I was intending to ask if there was any materials benefit to using an alloy over something like Delrin or other polymer. Or if it is just that certain alloys may be easy to mill and will also last a long while.
 

J-Rod10

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Rimmy said:
Spotty and co. I should have made my question a bit clearer. I was intending to ask if there was any materials benefit to using an alloy over something like Delrin or other polymer. Or if it is just that certain alloys may be easy to mill and will also last a long while.
Plastic is a pain in the ass to machine. It moves, a lot.
 

crazypj

Split personality, I fake being smart
irk miller said:
You can use delrin over urethane, no problem. It's not an uncommon swap in automotive high performance suspension systems and off-road suspensions.

I'm feeling too lazy to look it up, (had to take some 'good' prescription painkillers today 8) ) got a link for castable urethane suitable for bushings?
Whats the thermal tolerance? top engine mount gets pretty warm. Alloy mount there tends to 'fret' with heating / cooling cycles and vibration, some sort of (limited) movement plastic would probably be better IMHO
OP, you can always burn the originals out then re-cast new using original spacer/washer, it's easier than cutting up skateboard wheels ;)

irk miller said:
Haha. I like the solid mounted motor on my chopper. So pure.

Perv ;D
 

irk miller

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I love machining delrin. It works beautifully. As far as urethanes, I use 70A and 90A industrial polyurethanes for most of the parts I cast. Depends on the application, though. It can be done from 30A to 90A in the urethane I use.
 

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