RAF mast bushing

[rgraffeo]

Here are some pictures of the bushing that I made using Chuck Beaty's mold.
Its next to a RAF supplied bushing that I have as an extra.
Chuck gave the mold to Harry, who sent it to me.
I've made a few & still trying to get it right. Some look better than others.

[Gyropilot007]

Rudy:

Once you do get it right, I'd be interested in buying a couple from you.

Bob

[jjp77tex]

Same here..jack

[Harry_S.]

They're lookin' good, Rudy.

Rudy had told me he had located some gum rubber and was gonna try his hand at "cookin'" some donuts. I didn't get a chance to post that info to the other thread but...It's lookin' good.

Maybe CB will add a few hints here, Rudy. I know he commented to be carefull with the mold release. Another comment was to really "jam" the rubber into the mold to the point where you could just barely close the ends?!

Those look better than what I would have cooked. ;)


Cheers :)

[enewbold]

Rudy:
Once you do get it right, I'd be interested in buying a couple from you.
BobYes, me too, Rudy.

Ed

[C. Beaty]

Rudy, it is important that the mold be packet tight enough to get a little squeeze out- dingle berries that have to be trimmed.

If you have a set of postage scales with good resolution, weigh a good bushing, cut the same weight of gum + ½ square inch. The finished part will be in the neighborhood of 4 ounces.

Electric stove ovens have terrible control with about a 20º dead band and the dial numbers don’t mean much.

A 15 psi pressure cooker runs at 257º and would vulcanize the bushings in ~25 minutes once pop off pressure is reached. You could place the mold on a rack above the water level but water doesn’t hurt rubber.

Unvulcanized rubber will keep indefinitely if stored in a freezer.

[rgraffeo]

Mr. Chuck,
When I packed the mold tight so the end caps don't completely bottom out, the bushing seems to be a little longer that the original. Do you think this matters if its a little longer?

I tired a few that are the same length but don't seem to compress as well, the rolls of the rubber can still be seen.

Also guys the bushings are not for sale, I'll send you them free. If I can get them right. It shouldn't cost much to mail.
The tire shop gave me a small roll of rubber, when the roll is at the end he normally throws it away.

[jjp77tex]

Understand on the sales. However, you may get a nice STARBUCK's gift certificate in the return mail. :lol: :lol: :lol:

[Passin' Thru]

Ruddy, are you holding the rubber under compression during vulcanizing? On simular short-run projects I would place a weight on the top plate. During vulcanization the rubber runs almost like oil and the top plate under the weight setles down to the top of the mold and the excess is squished out.

[jjp77tex]

RAF (Canada) still has a few parts. They do have the 2 mast bushings. I just ordered a set. Need to call 306-463-6030. A 'micro electronics company' receptionist will answer, have her transfer you to MARY ANN in the warehouse (RAF parts) area. :wave: :wave: :wave:
Jack

[Mike Stone]

Please keep me on your list for a couple also.
N9897

[Harry_S.]

As CB has mentioned in another thread...do not use any sort of oil in contact with this donut. Use soapy water when inserting the bolt; I used plain water and it worked fine, just don't pound the bolt thru when the hole is dry.

You also may have a bit of resistance when sliding the cheek plates over the donut, so lubricate the ends and the plates will pass across real easy.


Cheers :)

[C. Beaty]

Mr. Chuck,
When I packed the mold tight so the end caps don't completely bottom out, the bushing seems to be a little longer that the original. Do you think this matters if its a little longer?

I tired a few that are the same length but don't seem to compress as well, the rolls of the rubber can still be seen.

Also guys the bushings are not for sale, I'll send you them free. If I can get them right. It shouldn't cost much to mail.
The tire shop gave me a small roll of rubber, when the roll is at the end he normally throws it away.

Rudy, you might use a stack of wave washers or even a stack of split lock washers sandwiched between plain washers when you tighten up the ½” bolt in the mold.

I used a little excess rubber and laid on the nut with a breaker bar which expands the water pipe slightly; the wall isn’t very thick after having been bored out to 1½” ID. I think it started out as 1¼” IPS water pipe.

Lubricating with silicone spray lube or Dow silicone grease won’t hurt anything when installing the bushing in the mast. Mineral oils cause slow swelling of natural rubber.

[rgraffeo]

Mr. Chuck,
I'm using the Dow silicone grease to lubricate the mold & bolt while heating.
It pops out with no trouble. I'm using a long enough bolt so I can screw the end caps until they bottom out.

Tonight at work I'll do some more testing.

Is this rubber natural rubber? I thought most rubber used for tires since WW2 was made from petroleum.

[Gyropilot007]

Rudy:

I'd like two of them and at least let me pay for the shipping.

Bob

[C. Beaty]

Cushion gum, Rudy, is the layer of rubber between carcass and tread. Typically, it is a natural rubber compound (lampblack, sulfur, and who knows what) but could be a synthetic/natural mix.

Tread rubber often is a synthetic/natural mix but mainline tire manufacturers treat their exact formulation as a trade secret.

Where you can see the layers from wrapping the stuff, you were shy of rubber but they may still be serviceable if the layers are properly bonded.

Don’t get any of the interlayer surfaces contaminated with silicone; you won’t get a bond with even minute traces of silicone.

[Harry_S.]

Mr. Chuck,
When I packed the mold tight so the end caps don't completely bottom out, the bushing seems to be a little longer that the original. Do you think this matters if its a little longer?





Hi Rudy,

CB has already given a tip on using wave washers and even hinted at using a breaker bar to get the caps down flush to the rims of the mold. ;)

That mold length is just about the max. length for the bushing. Any additional length and the cheek plates would be a bear to slide over the donut.

I would suggest 2.50 in. as the max. That's the dim. I just made off the RAF donut.

I think you're doin' just great, Rudy. Thank you.


Cheers :)

[rgraffeo]

Harry,
Been out of town, just got back.
2.5 inches is the length of the RAF bushing.
Some of the ones I made are longer, about 2.75.
I think they can be cut with a knife or hacksaw, what do you think?

Also I used Paul Bruty's idea about the spacer on the cheek plates:
I added 4-1/4" flat washers on the bolts that hold the pre-rotator cable guide. Between the cheek plates the pre-rotator cable guide has 2 bolts. I placed 1 washer between the cheek plate & pre-rotator cable guide on each side. This gives a little extra space so the check plate does not rub against the top of the teflon sheets.

[dragonflyerthom]

Hi Rudy

I am interested also. I will have to pay shipping if you can do it.

[Harry_S.]

Harry,
Been out of town, just got back.
2.5 inches is the length of the RAF bushing.
Some of the ones I made are longer, about 2.75.
I think they can be cut with a knife or hacksaw, what do you think?





I cut some slices off an old RAF donut with the bandsaw. Did a real clean square cut job.

I would try to keep 'em at 2.5 in. tho, Rudy. JMO.

I think you're doing real good. You'll make a lot of fellas glad to get one.


Cheers :)

[rgraffeo]

Today I was able to get more "free" rubber from the tire shop.
Soon I'll make another try at perfecting the bushing.

[Harry_S.]

Good show, Rudy. I'm sure you seek perfection in these bushings but I believe a few small pin holes should not be cause for rejection. As you know the bushing is rather solid, but resilient when cured.

Maybe section cut one or two questionable items and see what it looks like?!


Cheers :)

[rgraffeo]

Guys,
PM me your mailing address so I can send you 2 bushings each.
I have about 10 that are "decent" & as time permits I'll make more this weekend.

[Harry_S.]

Ya dun good, Rudy. We all thank you :D...and CB as well. ;)


Cheers :)

[jjp77tex]

Can I get a set also?
:hail: :hail: :hail: :hail:

[rgraffeo]

Tomorrow I'll see about mailing some to:
Wayne Hubbs
Bob McGuire
Mike Stone
Thom Francis
Jack PM your address to me.

Remember these are not perfect, I tried my best.

[rgraffeo]

I believe that I sent bushings to everyone that wanted them.
I hope ya'll can use them.

[dragonflyerthom]

I would just like to say thank you to Rudy G. He has done a real nice job on these bushing and they look like they will hold up really well.

Thanks again Rudy.

[WHUBBS]

Rudy, i received the two you shipped me and they look very good, will send you postage etc.

Just for your information, i worked for firestone tire and rubber for about 17 years formulating brake lining for cars and trucks, for the most part, but a little rubber compounding, also, and have an instrument that is called a SHORE-D which measures the hardness of the rubber. i checked your two parts all over, including the ends and got a reading of 10 to 15. if i had an origional one that had not been used, i would love to see the difference between the two. i just purchased a new set or tires form bridgestone and on the tread surface i averaged from 15 to 20 shore-D.


Wayne

[rgraffeo]

Wayne,
Not sure what your talking about but Chuck Beaty is the one that made the mold & figured out how to make them. He passed the information to Harry, who passed it to me.

[WHUBBS]

Rudy, this instrument is an instrument that is used for quality control, with rubber companies, which measures variation in density of the rubber all around the part, that has been molded. just say for instance, you had more rubber stuffed into the mold on one side than the other, the side with most of the rubber would get more pressure on it, than the side with less rubber, as it is being molded. when this happens, the side with less rubber will get a lower reading, which is showing the rubber in that area, is softer, the side with the most rubber will get a higher number, showing it is harder on that side. your parts were pretty close in hardness all way around the part, showing you have good even pressure and rubber distribution in your mold. my only problem is, i do not have a baseline to know what is good or bad. if i had an RAF regular production bushing, to test, then i would know how close your parts are to production parts that are being sold by the RAf manufacturer. i really appreciate the parts you sent to me and all your work and will be installing one of them in the near future on my machine.

Wayne

[Arnie Madsen]

I have found this homebuilder rubber manufacture thread very informative.

WHUBBS .... your SHORE-D instrument test makes sense to me. I am not familiar with this tool. Do you have a picture and additional info ? Much appreciated.

[Harry_S.]

I have found this homebuilder rubber manufacture thread very informative.

WHUBBS .... your SHORE-D instrument test makes sense to me. I am not familiar with this tool. Do you have a picture and additional info ? Much appreciated.



I am posting these photos for Wayne. I'm sure Wayne will answer any questions pertaining to this instrument.


Cheers :)

[Gyropilot007]

Rudy:

I received the bushings....thank you very much!!!

Bob

[Iron]

Rudy I received the bushings this past week Thankyou it is appreciated Roy

[jjp77tex]

i need 2 more..somebody stole my 2 at a local fly-in

[Mike484]

Contact Paul Patterson, he may still have some.