Machineable Polymers for an Engine Mount...

[Blackout]

You also have to remember that they do swell when exposed to water & high humidity.

What swells?

 

[Brad Christy]

Chris,

What swells?

I was wondering the same thing..........

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

 

[jetpack]

Nylon swells with moisture, not acetol ie - Delrin.

UHMW has one of the highest impact strengths of any thermoplastic and has excellent abrasion resistance, tensile strength, energy absorption, resistance to stress, cracking, and coefficient of friction properties.

Choose whatever you want, it was a suggestion. Compare the price also. UHMW is $3.00 a pound compared to Delrin at $8.00 a pound.

Use a deburring tool or a single edged razor, not a metal file to shave burrs. If you use high speed cutters that are properly honed and clearanced, you really aren't left with any burr to speak of.

If your doing high accuracy work, use Delrin it will hold dimensions better. For motor mounts I think UHMW is better.

Carbon powder is sometimes used to color plastic black...it is cheaper than dyes. You will have more tool wear with black delrin due to the carbon and there is a difference when machining. A bit different in the chips it makes. I dont think its black dye used in black delrin, I suspect its carbon just from machining it. If anyone investigates what makes it black, post it I'm curious.

http://www.johnsonplastic.com/plastics.php

 

[SayMikey]

Nylon swells with moisture, not acetol ie - Delrin.
UHMW has one of the highest impact strengths of any thermoplastic and has excellent abrasion resistance, tensile strength, energy absorption, resistance to stress, cracking, and coefficient of friction properties.

Choose whatever you want, it was a suggestion. Compare the price also. UHMW is $3.00 a pound compared to Delrin at $8.00 a pound.

Use a deburring tool or a single edged razor, not a metal file to shave burrs. If you use high speed cutters that are properly honed and clearanced, you really aren't left with any burr to speak of.

If your doing high accuracy work, use Delrin it will hold dimensions better. For motor mounts I think UHMW is better.

Carbon powder is sometimes used to color plastic black...it is cheaper than dyes. You will have more tool wear with black delrin due to the carbon and there is a difference when machining. A bit different in the chips it makes.

http://www.johnsonplastic.com/plastics.php

I used black delrin and its perfect for the job

 

[optimax]

I machine a lot of UHMW I hate cutting the stuff you you need to cut this type of plastic with the sharpest milling cutteres you can get. I use regular vegatable cooking oil for taping aluminum work's great. I Cut a ton of Acetol and other various types of plastics. I machine my servo mounts out of black Acetol they work great. I need to make more.

 

[SayMikey]

I machine a lot of UHMW I hate cutting the stuff you you need to cut this type of plastic with the sharpest milling cutteres you can get. I use regular vegatable cooking oil for taping aluminum work's great. I Cut a ton of Acetol and other various types of plastics. I machine my servo mounts out of black Acetol they work great. I need to make more.

NO Acetol< my last girlfriend did not have one! OPT got a pic?

 

[Scott Wadlow]

I machine a lot of UHMW I hate cutting the stuff you you need to cut this type of plastic with the sharpest milling cutteres you can get. I use regular vegatable cooking oil for taping aluminum work's great. I Cut a ton of Acetol and other various types of plastics. I machine my servo mounts out of black Acetol they work great. I need to make more.

NO Acetol< my last girlfriend did not have one! OPT got a pic?

your a sick man Mikey

 

[Blackout]

O.K., so black Delrin works great for a machined engine mount, but I just want to make sure that it will absorb vibrations a little better than aluminum?? I don't expect it to be as good as a rubber mount, but if it is no better than aluminum as far as absorbing vibrations, I would just use aluminum.

Thanks.

 

[mark voorhies]

I machine a lot of UHMW I hate cutting the stuff you you need to cut this type of plastic with the sharpest milling cutteres you can get. I use regular vegatable cooking oil for taping aluminum work's great. I Cut a ton of Acetol and other various types of plastics. I machine my servo mounts out of black Acetol they work great. I need to make more.

NO Acetol< my last girlfriend did not have one! OPT got a pic?

your a sick man Mikey

Got a laugh out a me!

 

[Bill Gibson]

O.K., so black Delrin works great for a machined engine mount, but I just want to make sure that it will absorb vibrations a little better than aluminum?? I don't expect it to be as good as a rubber mount, but if it is no better than aluminum as far as absorbing vibrations, I would just use aluminum.
Thanks.

It does....its still softer than aluminum but not as soft as rubber...take a 1/4" piece of 6061 or even softer 3003 aluminum and try to bend it by hand, then a 1/4" piece of black delrin...almost anything to isolate metal to wood or fiberglass helps a little...may not even be noticeable to the ear, but rubber is the best as you already know!

 

[steve wood]

if your mounting the motor mounts solid and not using any kind of rubber to isolate them from the rest of the boat, it won't make any differance what kind of material you use, delrin, aluminum, uhmh, or unobtanium!

 

[Brad Christy]

Craig,

if your mounting the motor mounts solid and not using any kind of rubber to isolate them from the rest of the boat, it won't make any differance what kind of material you use, delrin, aluminum, uhmh, or unobtanium!

I have to agree with Steve. If you're not going to rubber mount an engine, you might as well use granite.

Just out of curiosity, what opposition do you have with rubber mounting an engine?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

 

[Blackout]

Craig,

if your mounting the motor mounts solid and not using any kind of rubber to isolate them from the rest of the boat, it won't make any differance what kind of material you use, delrin, aluminum, uhmh, or unobtanium!

I have to agree with Steve. If you're not going to rubber mount an engine, you might as well use granite.

Just out of curiosity, what opposition do you have with rubber mounting an engine?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

The Octura Hummdinger mount in my Skater .82 moved way too much. It made starting difficult, I had to hold the engine real good when starting. I switched to solid and it is much better. My Dumas Mach .40 is also solid mount, and I don't notice any major vibration issues.

I was going to give the Hummdinger a second chance, so I bought a new mount for my Speedmaster .45, but there are clearance issues with the mount and the needle on the OS 46 vxm. The Speedmaster mount will not work with the O.S. engine as there are case cracking issues with that engine so it needs to be supported better using the hummdinger style mount.

So, I am back to machining my own mount and I will give Delrin a try.

Why do boats need rubber mounts while helis and planes do not? Is it just the noise resonating from the hull?

Anyone investigate whether a rubber mount will allow an engine to move enough to cause added friction in the drive shaft tube?

 

[SayMikey]

Craig,

if your mounting the motor mounts solid and not using any kind of rubber to isolate them from the rest of the boat, it won't make any differance what kind of material you use, delrin, aluminum, uhmh, or unobtanium!

I have to agree with Steve. If you're not going to rubber mount an engine, you might as well use granite.

Just out of curiosity, what opposition do you have with rubber mounting an engine?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

The Octura Hummdinger mount in my Skater .82 moved way too much. It made starting difficult, I had to hold the engine real good when starting. I switched to solid and it is much better. My Dumas Mach .40 is also solid mount, and I don't notice any major vibration issues.

I was going to give the Hummdinger a second chance, so I bought a new mount for my Speedmaster .45, but there are clearance issues with the mount and the needle on the OS 46 vxm. The Speedmaster mount will not work with the O.S. engine as there are case cracking issues with that engine so it needs to be supported better using the hummdinger style mount.

So, I am back to machining my own mount and I will give Delrin a try.

Why do boats need rubber mounts while helis and planes do not? Is it just the noise resonating from the hull?

Anyone investigate whether a rubber mount will allow an engine to move enough to cause added friction in the drive shaft tube?

NOISE NOISE NOISE and vibration. Any boat with a rubber mount will live much longer

 

[Blackout]

Craig,

if your mounting the motor mounts solid and not using any kind of rubber to isolate them from the rest of the boat, it won't make any differance what kind of material you use, delrin, aluminum, uhmh, or unobtanium!

I have to agree with Steve. If you're not going to rubber mount an engine, you might as well use granite.

Just out of curiosity, what opposition do you have with rubber mounting an engine?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

The Octura Hummdinger mount in my Skater .82 moved way too much. It made starting difficult, I had to hold the engine real good when starting. I switched to solid and it is much better. My Dumas Mach .40 is also solid mount, and I don't notice any major vibration issues.

I was going to give the Hummdinger a second chance, so I bought a new mount for my Speedmaster .45, but there are clearance issues with the mount and the needle on the OS 46 vxm. The Speedmaster mount will not work with the O.S. engine as there are case cracking issues with that engine so it needs to be supported better using the hummdinger style mount.

So, I am back to machining my own mount and I will give Delrin a try.

Why do boats need rubber mounts while helis and planes do not? Is it just the noise resonating from the hull?

Anyone investigate whether a rubber mount will allow an engine to move enough to cause added friction in the drive shaft tube?

NOISE NOISE NOISE and vibration. Any boat with a rubber mount will live much longer

O.K., I understand the noise, from the engine being in a hull.

But, planes and helis last a long time without rubber mounts. There construction is no more durable than boats.

 

[jetpack]

Here's my thoughts on rubber mounts. I am sure they help protect the hull, radio gear, etc..., but due to the nature of one cylinder engines, they are never truely balanced.

With that said, and probably most can agree to it, I often wonder if soft mounts rob RPM's. I have noticed flying 1/2A control line planes, if your engine does not have strong mounts or is loose in the mounts, it robs RPM's and even the slightest amount can be felt and heard.

Probably has never been a true study on it, but I would think this would hold true to larger engines also where a soft mount could rob RPM's.

One thing that really cant be studied about something like that would be the harmonic balance where there is a sweet spot in the motor where its working range RPM produces none to very little vibration where it wouldn't matter if it's a solid mount or not.

I would like to see the RPM difference between soft mounts and hard mounts of an engine under its proper load on the bench.

It just seems to me a "loose" mounted engine is not going to perform as well as a solid mounted one.

Worn rubber inslulators are a good indication something there is being lost in power, and makes me even wonder if there is excessive rod knock caused because of soft mounts.

Whats your guesses?

I think I'll ask some r/c plane flyers who can use tach's that have switched to soft mounts if they have noticed any drops in RPM's.

 

[steve wood]

Here's my thoughts on rubber mounts. I am sure they help protect the hull, radio gear, etc..., but due to the nature of one cylinder engines, they are never truely balanced.
With that said, and probably most can agree to it, I often wonder if soft mounts rob RPM's. I have noticed flying 1/2A control line planes, if your engine does not have strong mounts or is loose in the mounts, it robs RPM's and even the slightest amount can be felt and heard.

Probably has never been a true study on it, but I would think this would hold true to larger engines also where a soft mount could rob RPM's.

One thing that really cant be studied about something like that would be the harmonic balance where there is a sweet spot in the motor where its working range RPM produces none to very little vibration where it wouldn't matter if it's a solid mount or not.

I would like to see the RPM difference between soft mounts and hard mounts of an engine under its proper load on the bench.

It just seems to me a "loose" mounted engine is not going to perform as well as a solid mounted one.

Worn rubber inslulators are a good indication something there is being lost in power, and makes me even wonder if there is excessive rod knock caused because of soft mounts.

Whats your guesses?

I think I'll ask some r/c plane flyers who can use tach's that have switched to soft mounts if they have noticed any drops in RPM's.

i'm some what of a youngster to rc boating, only been at it since 1979. back then no one used any type of anti vibration mount that i'm aware of. the crapshooter's, that i had came with solid oak rails that were about 6 inches long, that were glued into the corners on each side, then you drilled holes through the oak into the sides and installed nailes with epoxy, thats right nails. the nails were in there to help keep the vibration from breaking the glue joint. didn't help much, the rails still came out,and you had to repair about once a year. the actual mount was a solid piece of 3/8 aluminum plate that was screwed or bolted to the oak, sometimes the bolts were installed from the bottom with finishing washers, and flat washers with nylocks on top.

about the time greg huey took over they were using a solid piece of 66 nylon as a motor mount, this was bolted in and then drilled and tapped for the motor. this was my first experiance with an anti vibration mount, and it worked much better than the oak/or maple and aluminum plate.

then came the rubber mounts that we have today. what a differance

there is no way i would ever build an r/c boat of any kind that didn't have some type of cushion mount, the boats don't fall apart, and in my opinion run much better overall.

 

[jetpack]

Solid oak rails doesn't really sound like the best choice of wood for anything on a boat..lol. Pounding nails through the hull sounds even worse. Oak is one of those types of wood nothing glues to very well because if I remember right its consdered or classified as an "oily" type wood...maybe just hard to glue well, can't exactly remember. All I was taught was oak was good for hard wearing and strength, but needs either mechanical fasteners or its own pegs.

About solid mounting, I really wouldn't want to solid mount a boat motor either, just due to the nature of wood hulls. They crack all by themselves without any outside help it seems.

I've been planning a bunch of boats and still in the decision stage how to go about mounting the motors in each. They are not standard width cockpit hulls, some are under the standard 3" where a plate mount will have to be used, or a special made hanger if I decide to go with a split mount.

I've been kicking around the idea of using all plate mounts and using rubber washers over and under the plate bolts, along with plastic tube spacers to isolate any way the screw can hit the plate metal to metal.

A plate mount would even allow me to swap out different kinds of motors and still come up with the same coupler location, a direct custom fit plate that stays with each motor.

Not quite a soft mount but enough to take the sharpness out of the vibs.

 

[steve wood]

just look at cmdi eagles. don't need no plates

 

[Terry Keeley]

Here's my thoughts on rubber mounts. I am sure they help protect the hull, radio gear, etc..., but due to the nature of one cylinder engines, they are never truely balanced.
With that said, and probably most can agree to it, I often wonder if soft mounts rob RPM's. I have noticed flying 1/2A control line planes, if your engine does not have strong mounts or is loose in the mounts, it robs RPM's and even the slightest amount can be felt and heard.

Probably has never been a true study on it, but I would think this would hold true to larger engines also where a soft mount could rob RPM's.

One thing that really cant be studied about something like that would be the harmonic balance where there is a sweet spot in the motor where its working range RPM produces none to very little vibration where it wouldn't matter if it's a solid mount or not.

I would like to see the RPM difference between soft mounts and hard mounts of an engine under its proper load on the bench.

It just seems to me a "loose" mounted engine is not going to perform as well as a solid mounted one.

Worn rubber inslulators are a good indication something there is being lost in power, and makes me even wonder if there is excessive rod knock caused because of soft mounts.

Whats your guesses?

I think I'll ask some r/c plane flyers who can use tach's that have switched to soft mounts if they have noticed any drops in RPM's.

i'm some what of a youngster to rc boating, only been at it since 1979. back then no one used any type of anti vibration mount that i'm aware of. the crapshooter's, that i had came with solid oak rails that were about 6 inches long, that were glued into the corners on each side, then you drilled holes through the oak into the sides and installed nailes with epoxy, thats right nails. the nails were in there to help keep the vibration from breaking the glue joint. didn't help much, the rails still came out,and you had to repair about once a year. the actual mount was a solid piece of 3/8 aluminum plate that was screwed or bolted to the oak, sometimes the bolts were installed from the bottom with finishing washers, and flat washers with nylocks on top.

about the time greg huey took over they were using a solid piece of 66 nylon as a motor mount, this was bolted in and then drilled and tapped for the motor. this was my first experiance with an anti vibration mount, and it worked much better than the oak/or maple and aluminum plate.

then came the rubber mounts that we have today. what a differance

there is no way i would ever build an r/c boat of any kind that didn't have some type of cushion mount, the boats don't fall apart, and in my opinion run much better overall.

Remember all the K&B cases that broke under the lugs?