Hi, Have a Webra Bully 35cc that I'm apparently going to have to drill props for a 6 bolt mount. To date, I've only had to ream props for single bolt mounts, including my DLE30 which has an adapter installed. Been hoping to source a single bolt adapter to fit the bully, but no success so far. Even bought an extra prop hub hoping it might somehow be used to fab an adapter. Was advised that 3W bolt spacing was a match, and do have a DA\3W drill jig and bolt spacing does seem correct, . . . . but holes are 5mm and Bully bolts are 3.5mm, and the prop washer holes are 4mm. Have some concerns of just drilling 5mm holes, . . . . and still hoping for a single bolt adapter, . . . so looking to these forums for any advice or suggestions.


Thanks in advance for any advice or suggestions

t-man49 in Al

Club Saito 723

You should be using a counter bore with the correct size pilot to enlarge the hole in a propeller. Reaming it will not maintain it’s location. Dan.

When faced with this I have slid the prop in place on the center spindle shaft. Place a couple small globs of RTV on the washer and slide into place. Make sure the hole position will allow the prop to be located at around 1:00 to 2:00 position at the beginning of the compression stroke. When the RTV is dry slide the prop off with the washer attached and drill on a drill press using the washer as a guide. It's best to use a new bit to reduce chances of the bit walking.

Hello again and thanks for he replies.

Dan, the reamers I've been using are "step" reamers sold by the hobby shops to ream the prop center hole. There has always been a "step" that fits existing hole. Is this not the same purpose as the pilot on the counter bore you referenced?

Speed, nice to hear from you, and your advise does seem like the simplest method and which is probably what I'll do. K & S does show some 5mm brass tube with .45mm wall, . . . I may attempt to make a bushing for the drill jig I have as I to am concerned of the drill wandering.

Again, Many Thanks
Mike Brennan
t-man49 in Al

Hi Mike
Like you already know you have a couple of ways to tackle this issue, It sounds like you would rather go with a single bolt prop adapter, but if all else fails some bushings will also do the trick. But a 3.5 MM bolt is not the strongest item there is and a backfire or loose bolts or as you already said over sized holes could lead to a shearing problem.
I can make a single bolt set up I am sure W/O to much problem especially if you have the new prop hub, but I would need to have a look at things to make sure.Of course a drill guide with the proper sized holes in it could also be made so there are several ways of doing this to come up with a good safe set up that will last for years. Can you post some pics so I can see what it is were working with?
Richard.

Hello Cyberwolf, Many many thanks for your response here. I am aware of your machining skills since the DLE30's with their side mounted carbs and some of your engine building efforts. I do have an affinity for the single bolt, easier - yes, but also successfully used on current engines this size as well as larger displacements previously. Currently, I am packing for work out of town but would appreciate being in touch, probably next Saturday to make some arrangements. Again your response and offer is greatly appreciated

Mike Brennan
[email protected]

Mike, as long as you are using a drill with a pilot at the end and it is mounted in a drill press that you have checked for perpendicularity you should be in great shape. I read into your post that you were using a tapered reamer and doing it by hand a definite no-no. I am using a 3/8 inch counter bore with a ¼ inch pilot for my engine and props. One big advantage is that that is what the propeller manufacturer recommended. The pilot is solid around the edges and the counter bore blades cut downward in to the prop parallel to the prop face. It’s a very accurately placed hole. Dan.

Hi, am hoping to be in touch with Cyberwolf, as after many weekends of looking, have finally located the extra prop hub, purchased over a year ago. Did attempt to PM, but as no record shows in RCU, I suspect it hasn't been received.
My e-mail is in a previous post, do hope to hear from you Richard and thanks in advance.

Mike Brennan