actual Size of JETT/Nelson mounts
 

Hey guys, I am tweaking my composite molds and would like to know the exact size of the backplate mounts for Jett & Nelsons. I have a SS and it is 2.271 across the top and 2.274 across the sides. I know the minimum is 2.25, but are the Nelson & JETT mounts slightly larger? Right now my plug is exactly 2.25 square, but I want it to fit the 428 backplates EXACTLY! http://www.rcuniverse.com/forum/js/f...sn/biggrin.gif If a couple of you with each engine could check it and let me know, I would be in your debt! http://www.rcuniverse.com/forum/js/f...sn/biggrin.gif

Thanks,

RE: actual Size of JETT/Nelson mounts
 

Just order one from Performance Specialties of Jett - they don't cost much in relation to time and material formaking molds.


dan

RE: actual Size of JETT/Nelson mounts
 

OK, let me back up a bit! :D My mold is for the fuselage of my 428 plane. I designed the plug for the molds all around minimums. as the rulebook state 2.25" square for the firewall, so this is what I used for the original plugs. Since we all know revisions are inevitable, I made some plug revisions and am doing my last checks prior to committing the revised plug to the molding process and don't want to make a costly mistake. Since all I currently have on hand is a Nelson SS for 428, that is all I can measure. To my amazement, the mount was larger than the required measurement! So, in an attempt to have it fit as well as I can, I would like a few back plate measurements. If I make it too big or too small, it is just unneeded drag.

Thanks again,

RE: actual Size of JETT/Nelson mounts
 

Scott,

I just measured my LS backplate (New last spring) with an accurate caliper.

Side to side (with head at 9 oclock from the front)  2.251"
Top to bottom 2.254"

Looks like tolerance to me, should be good to go 2 1/4" square.

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RE: actual Size of JETT/Nelson mounts
 

Thank you Dave, I appreciate that. ;)

RE: actual Size of JETT/Nelson mounts
 

Hey Scott,

Breaking news

NMPRA has decided to make all 428 planes 6 inches wide at the nose....tapered down to a point at the tail....

Also , it should have 78 inch wings.....

Hope that helps,,

Phil

RE: actual Size of JETT/Nelson mounts
 

LOL Phil, but the NMPRA does not change the rules.

ANY AMA member can submit a rules proposal that will be reviewed and voted on by the AMA Contest Racing Board.

The NMPRA has nothing to do with the rules as they pretty much support existing AMA rulebook classes.

RE: actual Size of JETT/Nelson mounts
 

Hey Dave,  Oh yea that's right....

I meant to say that the AMA will soon be changing the rules about Q-500 planes.

I didn't want Scott to build a plane too small. I like to look after him and help him every chance I get......

And since I'll be competing against him in that class, I want him to have the "inside scoop" so he can build a big ole fat heavy honkin Quickie plane....

LOL LOL  

That might be the only way I'll be able to beat him....Know what I mean , Vern?  

Phil

 

Just trying to help out a fellow racer......LOL</p>

RE: actual Size of JETT/Nelson mounts
 

For what it's worth - just measured a couple of Jett BSE Q500 square mounts - 2.253 x 2.253 for one, and another was 2.251 x 2.249. That one had marks on it (bought the engine used) like it had been sanded just a bit on the sides.

Also, the rules state the firewall has to be 2.25" square minimum - not the mount. I'd just make sure your fuse comes out of the mold at least 2.25" square at the front end.

RE: actual Size of JETT/Nelson mounts
 

Thanks again guys, the mistake was mine. I came home and went to re-check my SS, and I noticed the numbers were flashing on my digital calipers. [:@] I changed the battery and guess what? I measured 2.2520 x 2.2515 on the back plate! :eek: I should have known they wouldn't be that far out... I put the SS on the front of the plug, and you can just barely feel an edge.

      Phil, don't you worry buddy, I will make sure they come out on the fat and heavy side just for you!! You know I am a stickler for the rules, and my planes have always met the rules (even if just by the <font size="2">smallest</font> of margin's! ;)) But if you want me to make you some big, fat heavy ones, I will make them just for you! :)

      Thanks Fizzwater2 for the Jett measurements, I will more than likely go with a cast 428 engine when I take the plunge so that is good to know. I will leave my firewall at 2.25 square and call it good! ;) Just out of curiosity, do the mufflers for the Jett LS and the Nelson LS have the same dimensions and spacing at the rear near the exhaust? I ask because my gear and fuse are pretty close at that point. If I need to adjust it, I want to do it now! These revisions are a pain in the, ... well, ... you know what! [:@]

Thanks a ton guys, [8D]

RE: actual Size of JETT/Nelson mounts
 

Ok, heres a gray rule question for you experts.

The rule says the firewall has to be 2 1/4" square minimum, but what part of the firewall? The front, or if its a 1/2" firewall the back?

mmmm.....

RE: actual Size of JETT/Nelson mounts
 

I'm pretty sure that we all know what the "intent" was, but you are right, it's not PRECISELY defined in the rules, which allows for "creative interpretation of the rules"... for those who like to do such things.