OS MAX-S 35 mufflers

I have a tongue muffler which means I'll have to drill out the holes on the side of the stack - does it matter whether I drill and tap the holes and mount the muffler from the muffler side or drill clearance holes and mount the muffler from the stack side.

It seems mounting the muffler from the muffler side will mean I won't have to loose the 2 fins behind the stack.

The two engines GMA did for me have the holes drilled all the way through. I like this as now they are the same as the FP-25 and any muffler that fits the FP will also fit my S's

I do beleave that most of the mufflers out there call for the OUTSIDE to be drilled. Mine are like that. I also have one that the inside holes are 4/40 and I can put on a home made muffler. Drill the outside. Make sure that you plug the exhaust stack. I use ear plugs that expand to use as plugs. Drill from the back to the front. I make sure that the exhaust stack is 90 to the drill. The flange makes a good steady platform.

Scott(Drill slow)Riese

>Drill from the back to
>the front. I make sure
>that the exhaust stack is
>90 to the drill. The
>flange makes a good steady
>platform.
>
>Scott(Drill slow)Riese

This is important. I have several engines that were drilled from the front (exhaust) side and the holes are very crooked. I may have to weld the stack shut and start over. Lay the stack flat on the drill press and use the two small "fins" on the back side of the exhaust as guides. Drill as if you were in the exact center of the arc of the stack and you will be "right on".

What size drill (mm) for a 4-40 tap?

Apart from a reply to my previous question (re 4-40 drill size) I have another question!

Any 35 size mufflers around that have only 1" between mounting holes? This is for an OS-Max 2 35.

Tony; drill size for a 4-40 is
#43 drill, .0890 inch, 2.2606 MM

2.606mm drill are a bit rare - even here in the UK - will a 2.5mm do?

Tone

A number 43 drill should be readily available from most engineering supply shops. Don't let the extended decimal fractions frighten you.

I think you may have misread the original mm size - if you go to 2.5 from 2.26 (not from 2.6), you will have a very sloppy fit...

I guess I am missing your question, but why not just tap for a similar sized metric bolt - assuming that will be more convenient for you. Also note the 4-40 size was 2.26mm not 2.6mm (I forgot the exact quoted size, but it is different than the value in your reply).

Vernon: I've never had any success with 'engineering supply shops' - the ones I've found only ever want to sell you 50 of something - perhaps I'm looking in the wrong place?

Both: Yes I did misread the drill size - still I'm a programmer and what programmer ever reads anything properly?

Alan: I already have half a dozen 4-40 taps the minimum an 'engineering supply company' would sell me...

Tony

Tony,

have a look at the Blackgates website.

http://www.blackgates.co.uk

It's a model engineering supplier and will supply individual drills from the any of the number/letter/imperial/metric range.

They also do mail order. You might as well get a catalogue as there are lots of bits and pieces that will come in handy e.g. BA taps and dies, sold singly.

That looks a good place Vernon I'll get their catalogue.

However I now need some 2" long 4-40 allen bolts to mount silencers and my usual supplier (AHC Camberley - usually pretty good) want £40 for a 100 any ideas who in the UK might do them?

If not could I send some money to one of out American pals to buy some for me?

I would be willing to get them for you, but I would like to know where to get 2 inch long 4-40 bolts, also. However, why do you need 2 inch long bolts to mount mufflers, er, silencers? 1 1/4 inch or even 1 inch will normally do.

Tony,

I don't know of a cheap source of screws of that thread form. However, you might consider using threaded rods from a local hobby shop if you have one. My local model shop has threaded rods that coud be used with appropriate nuts. I am not sure of the thread form though, e.g. metric, 4-40 or what. It could involve you drilling out the threads in the silencer or engine to clearance size for the threaded rods. This is likely to be cheaper than £40 though a bit more of a hassle.

I still am not sure why you need the 2 inch length for the 4-40 bolt. But I needed one of that length once for a tip weight box that got too deep and had a 4-40 blind nut already insalled inside. I got a metric bolt slightly longer of that length and retapped the end to 4-40. Cheap and simple. The metric bolts should be readily available to you and a 4-40 die is easy to obtain (or one of us could get it for you.)

>> I would be willing to get them for you, but I would like to know where to get 2 inch long 4-40 bolts, also. However, why do you need 2 inch long bolts to mount mufflers, er, silencers? 1 1/4 inch or even 1 inch will normally do.

I'm using a small strap that only goes around 1/4 of the cylinder circumference.

I've mounted one of your tongue mufflers to a Merco 35 using this strap and the bolts are 1 1/2" (can't remember where they came from - probably with one of the mufflers I've got from you) so probably 1 1/2" 4-40 bolts would do.

1 1/2 inch bolts we have got, can get. If you need or want some of these I can send them. Bolts alone, or whatever.