Bob Pastorello

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For my GP Ultimate, needing 2" standoffs. Who has info on someone that makes alum standoffs? Or alternate source? Already thinking of 2" hardwood dowels, but concerned about additional nose weight 4 of those would make.

Suggestions?

Chris Moon

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Hi Bob...Call Don at Don's Hobby Shop in Salina, KS. He stocks several sizes.

vertical ts

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http://www.geocities.com/roger_forgues/engstandoff.html

I just ordered standoffs myself.Roger is very easy to deal with.

Bob Pastorello

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Roger's is the one I couldn't remember! Thank you!

I remember from before - he was a great supplier, top-notch quality. The anodizing is a nice touch, too!

scotsman212

I make these stand-offs too. The way I do it, it can work for any size engine just by matching the bolt sizes for the engine size. Here's how I do it. If you've got access to a mini-lath, you can do it yourself. First I recommend that strips of oak or the hardwood of your choice be epoxied to the back or inside of the firewall where the mounting holes will be drilled... either two vertically or horizontally. The thickness and width of these strips is dictated by the size of the engine and I always over engineer in this area so I can sleep good at night. If these strips hold as they should, it's for darn sure the stand-off will stay in place. Next, position the engine mounting plate or engine support flanges where it needs to be on the firewall and mark with a self-centering punch. For additional holding power, I drill the holes small enough that the chosen bolt size has to tap its way into the hole.

The actual stand-off I make like this: I use a high tinsel strength bold that will reach far enough through the firewall mounting holes and hardwood strips that a washer and nut will attach(even though I've caused the bolt to tap into the hardwood). The bolt: first: I chuck it into the lath and face off about two-thirds of the head; then, without removing it from the chuck, I drill a hole the full length of the bolt into which I will later tap threads to match the socket-head bolt that will eventually be the mounting bolt. I use a hand tapping machine I got from Harbor Freight and carefully advance the right size tap the whole length of the bolt. The remaining bolt head makes a nice flat "pillow" for the aluminum rod to rest on that actually determins the standoff distance.

Next: I mount the bolts, usually 4, into the firewall. The one third of the bolt head that's left is kinda small to keep a socket on so I us one of the mounting bolts with a nut to use as a jam-nut. I screw the socket head bolt into the tapped bolt head and take it in about half an inch or a little more then run the jam-nut up to the head and crank it down. Now, you can use the socket head to drive the main mounting bolt into the undersized hole I recommended earlier. Once you have the main mounting bolt screwed all the way in, set the nut and washer on the back of the firewall strips. Now you can loosen the jam nut and easily remove the socket head bolt. Do this for all four of the main mounting bolts and you're done with the "hard" stuff.

You can now chose the length of the stand off by choosing the length of the bolt you need to get it plus adding some length to reach into the firewall mounting bolt you've just mounted. If it makes you feel better, you could run the socket head bolt all the way through the mounting bolt and put a washer and nut on it too but a little Lock-Tite plus the lock washer on the head of the socket head and that should hold it ok. There should be a fair amount of threads screwed into firewall bolt and I use the smaller tap for the threads when I'm cutting so the socket heads screw in pretty tight. Use a good tapping lub and don't get in a hurry... remember, you're tapping into a fairly hard bolt. I remove the tap and clean the crap out the tap a number of times on the way to the other end of the bolt.

Next I use the lathe again to cut and drill the needed lengths of aluminum rod... half to five-eights diameter depending on the diameter of the socket head bolt you use. The rod is carefully faced and drilled full length too and to a slip-fit for the size of the socket-head bolt you've chosen to use.

The mounting procedure is pretty obvious... run the socket-head bolt through the engine mount (with small lock washers under the socket heads), slip the aluminum stand-off onto the bolt and screw it into the waiting bolts mounted in the firewall. Care needs to be taken here and it's a good idea to mic the lengths of the aluminum tubes you've made to be sure the engine isn't ultimately pitched at an undesirable angle. On the other hand, this is an easy way to build in whatever angle of pitch you wish. It takes just a few thousandths to achieve a fair amount of pitch at the prop hub. Be sure to mark the tubes for reinstallation position if you do this!

This may seem a little involved but it makes for a nice clean installation and a safe easy way to mount and dismount engines as the socket heads are all that need to be removed and this is easily done from the front of the installation. The weight is minimal because a lot of the metal is drilled out and/or removed from the main firewall mounting bolt(s). Because of their inherent strength, the mounting bolts need to be only slightly larger than the diameter of the socket heads... enough for the threads plus a quarter to give an eighth all around the threads. For a more permanent installation, the main mounting bolts could be epoxied in place but this disallows the easy mounting of future engine installations should a major difference in size be desired. Try it, I think you'll like it. There's undoubtedly lots of ways to do this but this is the way I do it and I've never lost an engine. I don't have to ask you to let me know what you think because I know you will!!! --Bob

Bob Pastorello

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scotsman - THAT is a well-thought-out design that likely works VERY well. My only reservation is the requirement of equipment that isn't sitting in MY shop

A very good explanation, and one that likely should be more widely used! I like the idea of basically making "threaded mounting bases" at the firewall for the standoffs to bolt up to. Great idea, I think.

I need a more conventional (read cheaper, less sophisticated equipment demands) solution....[&o]

Thanks for sharing your method; I like it.



Now, if I could just figure out how to drill a hole in the center of a hardwood dowel that is 2" long....[:-]

geardaddy

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I can make them in any length you need in either 1/2 or 3/4 as i have a lot of that on hand, no anodize however. And 6061 is pretty light already. Am also in between jobs.

scotsman212

This is how I'd do it. If you don't have one, find a friend with a drill press. I have a big radial arm floor model but I mostly use the heck out of my little $39 bench model. If you can get to one of these, use a "V" block and clamp the dowel in the block and stand the block up on its end effectively holding the dowel perfectly vertical. Be carful to not let the end of the dowel stick out past the end of the block. Also, on these little drill presses, some of the tables have a left/right tilt angle adjustment you can get to underneith the table so be sure the table is set to an exact right-angle to the bit in the chuck. I'd use a shaprp pencil or scribe (pencil shows up better) and straight edge and draw a perfect "+" across the end to be drilled to find dead center.

A good way to arrive at DC (dead center) would be to lay the dowel in the "V" block flat on the drill-press table , use playing cards as schems to elivate the "V" block so that the straight edge falls across the widest diamiter of the dowel. When you're happy with this setting, draw the first line then rotate the dowel in the "V" block 90 degrees and draw the second line. Now you should have a good centering point.

When you drill, use a centering bit first to start the hole. Use the smallest of the centering bits first and go up from there if you need to. These usually come in a set of three or four and can be had through Grizzly or Harbor Freight for like 3-4 or 5 bucks. A regular drill will wonder about if you try to start with it because of the flutes grabbing and offcentering. (or you could try starting with a few really tiny bits and work up but the centering bits are strong enough not to wonder about on the face of the dowel) The centering drills are about two and a half inches long with a drill point on both ends. They are blunt or rounded and if you introduce their tips slowly into the end of your dowel, it should center nicely without jumping around.

It wouldn't be a bad idea to clamp a short piece of angle to the table for a "fence" so you can hold the block against it and prevent slippage while drilling, using the playing cards again to adjust the distance from the "fence" you just clamped. The tip on the centering bit is only about 3/16 to 1/4 long or less and then flares to give a counter-sink effect in whatever you're drilling. I'd carefully let it counter-sink just a little... enough so the flutes on your hi-speed bit couldn't grab any part of the flat surface of the dowel. Just like the aluminum I mentioned earlier, it's important to make the ends as close to angel-less(???) as possible and keep them as close to the same length as possible too. Another consideration is that the wood will compress as you begin to tighten everything up so check for where the prop hub is pointed as you tighten. I'd also use nothig but hardwood dowel... soft pine or other "soft" woods will not stand up to your use.

It just occured to me that, using this methodology, you could still use aluminum rod and do it all the same way. Another option might be to use a series of small thin aluminum washers on the mounting bolt with a larger washer for them to rest on especially on the firewall to distribute the compression the firewall will experience. Still another option would be to use small plastic pipe cut to length. Any tough material with a hole already in it will spare you the labor of trying to drill the dowel or rod. Hope this helps... Regards and have a good week-end... what's left of it! --Bob