I seem to have lost the head bolts for an OS MAX .35 glow engine and am not sure of what to get for replacement .Does anybody have the correct size or a good website with engine parts on it

These people sell the OS engines and parts

http://www.towerhobbies.com/

The OS 35 has been out of production for many years.

There is a slight chance that the head bolts for a OS 40LA engine would work?

If they work you will need 2 sets as the LA only has 4 head bolts and you need 6.

They are a metric size, M2.5 . Dubro has them.

Dwreefs,


Don't bother ordering these bolts from a hobby supplier...

Just take the engine to the nearest technical supply shop and go to where fasteners are sold.


You will easily find the metric bolt size, with any head (flat, Phillips, or hex socket) and they will only cost you 'a dime a dozen'.

I am sure Alberta Canada has enough metric fasteners available. You will find new ones for the back-plate also and a stronger prop-nut.

I've just checked 3 of my .35's and they're 3mm x 10mm long. The thread pitch seems to be .8mm as far as I can tell.

Ah my bad, the MAX 60's and up are M3.5

thanks for your help I'll pick up some 3mm when I get to the Hobby store

http://www2.towerhobbies.com/cgi-bin...?&I=LXE023&P=7

Jim,


Are you sure these will fit?

If the bolt is too short, it will not engage enough threads in the crankcase and this could prevent fully tightening the bolts (or could potentially destroy the threads...).
If they are too long (not in this case, at 10 mm length), they may run out of threads/depth, before the head is battened down tightly.

If DWR has one of the original bolts, he should measure them. If not, in liew of the originals, a technical supply house is better than paying $2.98 for eight bolts (he'll need two sets) and not being sure they will fit. He'll have more of a choice.

The MVVS .40 frame engines uses 3 mm x 14 mm thread length (17 mm total length).
The MVVS .21 frame engines uses 2.5 mm x 10 mm thread length (12.5 mm total length).

I think the OS.35 would need longer bolts, to take the head thickness + the distance between the head and the crankcase and still go 7.5 mm into the crankcase.

Bolts should engage to a depth of at lease 2.5 times the diameter of the thread - 7.5 mm in this case.

There is also the problem of thread pitch. Some of the earlier engines from some countries had thread pitches on the screws that do not correspond with today's standards

Didn't you read my post #6? I pulled a head screw from 2 of my Max-S 35's and measured them. The shank is 10mm long. I just pulled a screw from one of my Max-H 35's and they're the same.

Brian,


The specs in the Tower page says 'Length'; not shank length.

I am not sure what 'length' means.


See this [link=http://www.microfasteners.com/catalog/products/METSCM.cfm]Microfasteners page[/link]... 20 bolts are $1.85-$2.00.

Also, the normal, standard thread pitch for a 3 mm diameter bolt is 0.5 mm.

...You wrote 0.8 mm... Are you sure?


A tech-shop that sells metric bolts is the only option to be sure you get the correct bolts.

Good luck fellows on finding the head screws that you need for your older model OS Max .35 engines ..... the head screw (backplate screw is exact same size) that you need is indeed exactly 10 mm in length (measurment does not include head) and is 3 mm in diameter, but unfortunately with a .6 mm pitch. Like I say fellows, GOOD LUCK ..... you are going to need it! If anyone finds a source for 3mm x .6mm bolts please give me a clue, will you? Thanks Much!

Donald Garry

Give this guy a ring or drop him a line

This may not help much but a 5BA screw is almost exactly 3mm with a .59mm pitch.

Here you go, a screw set for the .35 r/c and he's in canada also.

http://cgi.ebay.com/FOR-OS-MAX-H35-2...QQcmdZViewItem

BTW, anyone here have a spare connecting rod for a .35 R/C (same eng)? I NEED one of those for my engine.

Mike

Before I would ever pay 7 bucks (plus postage) for 10 short screws, I will buy myself a 3mm x .6mm round die and make my own from the much more available standard size 3.5mm x .6 mm screws!
Click here: http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=21625423
Just turn down some of the common 3.5mm screws available from 'Micro Fasteners' and then re-thread with this die.