Pinions and grub screws

[Andrew Rowland]

Well i'm needing a little help guys...

I have my little gearbox and I want to set it up as an experiment with the lovely 11t pinion that Chris W has given me very kindly.

There are two linked questions. If I can answer 2. I will not need 1.!:

1. The sleeves that AB slotsport sell to reduce 2mm bore pinions down to 1.5mm whilst tight inside the pinion, slip easily onto the motor shaft. I have only ever had push fit before and cannot solder it so can I glue it?

2. The hub that the slimline motor has is around 4.6mm diameter. So the hole in the gearbox through which the pinion mounted on the motor must pass is corrispondingly 4.6mm. The pinion at 11t is of course around 5mm so cannot pass through it!

So I got to thinking that maybe I could drill and tap the pinion on with a grub screw. The pinion at 11t has plenty of 'meat' and I have a very short grub screw. A flat spot on the motor shaft would ensure no slippage.
So the question is what is the thread called on the usual slot.it grub screw? Is it M2x0.4? By any chance?

1.6mm drill I assume?

Anyone done this?

HELP!
Andi

[old23]

Andi, I would simply use a good liquid threadlocker (like Permatex red or Loctite) to fasten the sleeve and then the pinion to the motor shaft with the motor in place. If you want to remove it later, a little heat from a soldering iron should free it easily.

Stewart

[slo]

You need to consider that the AB sleeve is most probably hardened and if it can be be tapped at all. Secondly, the pinion is small, the proportion percentage of material removed is greater than it is on crowns or wheels so you may have to also put a grub on the opposite side to bring the pinion back in balance. The commercially available pinions with grubs I have seen have 2 grub screws.
Slot It grubs are 2M x 0.4 and the correct tapping drill for M2 is 1.6mm 1/16" drill will do too

I use Loctite 262 or 263 for metal pinions
Loctite 406 super glue or just plain old thin Zap a Gap on plastic pinions even though they are generally push fit. Be care not to glue the motor bearing

[Andrew Rowland]

Thanks for the feedback. Especially interesting to see the AB sleeve is hardened.

Hmm, i'll try and post a photo but anyone who has one of these gearboxes will appreciate that gluing it might be troublesome. Plus sending a glued pinion off on a proxy series across the pond seems to be a slightly suicidal approach.....

I have a plan! What If I drill a 0.5mm hole right through the pinion (from base of teeth) and through the motor shaft. Then pop a little pin in and glue that?

I can see drilling through three different materials, so having to cross 4 material boundaries a bit tricky with a 0.5mm bit especially with the hardened sleeve. Any thoughts on this?

Cheers
Andi

[David Mitcham]

Hi Andi

I used Loctite on the pinion for one of my VRAA 2015 cars and it was fine. I've also used it for the pinion on the motor in the Policar chassis for my Ferrari 312 and so far its been no problem.

Best Regards

David

[Phil Kalbfell]

I will agree with David, I have used Loctite Super Retaing compounds in Industrial applications with no problems.
I think 648 is the Loctite number af the one for shafts and pulliey.

[Andrew Rowland]

Ok, ok, you've all convinced me! I'll give it a go.
Thanks
Andi

[chrisguyw]

Andi, The best way to secure the pinion/sleeve to the motor shaft is by soldering . and since you will be screwing/gluing the motor can to the motor box bulkhead, it will not hurt at all to open up the hole on the bulkhead, to let the pinion pass through.

Having said that, it is perfectly acceptable to use a permanent thread locker (I use locktite "Red" ) for this purpose.....like others, I have done this numerous times without issue.

And a couple of other do's and dont's..........do, apply the thread locker to the inside of the pinion sleeve, and not the motor shaft....this will force the glue into the sleeve (where you want it) and away from the motor bushing.
Don't.... use any CA for securing the pinion/sleeve...CA has terrible shear strength, and just will not last.

I am sure you already knew all this!!

Cheers
Chris Walker

[chrisguyw]

Hello again, I just thought of a few more things in addition to the above....again, I am sure you know all this, but, just in case.

1/ You will need to measure/trim the length of the motor shaft...the motor I sent has a shaft that is too long for your chassis. To trim the shaft, apply some power to the motor, and cut with a Dremel/cut off disc. This will give a much nicer cut.

2/ If you need to trim the length of the pinion,....install the pinion on the sleeve, chuck the long end of the sleeve into an electric drill, spin, and trim the pinion to the desired length, To cut the remaining long end of the sleeve, slip the pinion/sleeve on to a spare 1.5mm shaft/piece of piano wire etc., and use the dremel/cut-off disc to trim.....you can use a slightly larger dia. piece of tubing behind the back edge of the pinion, so it won't "walk" as you trim it.

3/ Make the sleeve as long as possible......it will help in "squaring" the pinion/sleeve on the shaft, and will provide more gluing area.

4/When you install the pinion/sleeve on the motor shaft (permanent thread locker), rotate it once or twice to ensure that the thread locker coats the entire inner surface of the sleeve.......the sleeves are not a perfect fit on the motor shaft, and in addition to point #3,will provide the best opportunity for the pinion to go on "square", and,will also provide the strongest bond.

Cheers
Chris Walker

[Andrew Rowland]

Hi Chris

First thank you for your help. I am so happy to get this sort of help. The more detail the better and although I 'guessed SOME of it' I certainly didn't know all of it so its always useful to hear it all spelt out.

The problem with the Policar motor pod is that it is plastic so the screw fixing doesn't so much hold the motor in place as just stop it rotating so opeing up the hole to let the pinion pass is fraught with misalignment issues. So i'm going to resist that option.

I'm ordering some thread lock so that is my permanent solution for the series but right now I need the ability to put it on and take it off to test the ideas so i've used CA tonight and it has worked so far for the evening.

The other issue is that with these gearboxes you have to have the crown in when you put the motor / pinion combo in. So I found I could balance the pinion in place and slip the motor shaft through the motor mount hole and find the end of the pinion and then push it fully in and clip it down.

All looking good.

I found the pinion you sent me is a very tight fit onto the sleeve so no risk of slippage there. The pinion can be used full length so I won't cut it down. The motor shaft was indeed too long and I have already cut that down with the dremel as you indicated.

So i've had a good run in with a part used 9v battery for about half hour and then raced a few laps against the clock. The car seems very different from my other cars but of course it would....

So I have two real issues:

1. Should I partly flat spot the motor shaft so the locktite can form a physical blob to prevent rotation?

2. What tyres should I be using. Mine give no grip at all.....

I don't think i'm going to be very competitive as the car feels sluggish but as a first try its going to be interesting....

Thanks for all the help and of course the parts Chris.

Cheers
Andi

[Phil Kalbfell]

If this car is for a Proxy Race best thing is to look at the car Ito from the previous event and see what tyres were fitted to the top cars.
VRAA mainly seem to use PG tyres.

[chrisguyw]

Apr 14, 2016 16:25:49 GMT -5 Andrew Rowland said:

Hi Chris



The problem with the Policar motor pod is that it is plastic so the screw fixing doesn't so much hold the motor in place as just stop it rotating so opeing up the hole to let the pinion pass is fraught with misalignment issues. So i'm going to resist that option.

The other issue is that with these gearboxes you have to have the crown in when you put the motor / pinion combo in. So I found I could balance the pinion in place and slip the motor shaft through the motor mount hole and find the end of the pinion and then push it fully in and clip it down.


So I have two real issues:

1. Should I partly flat spot the motor shaft so the locktite can form a physical blob to prevent rotation?

2. What tyres should I be using. Mine give no grip at all.....

I don't think i'm going to be very competitive as the car feels sluggish but as a first try its going to be interesting....

Thanks for all the help and of course the parts Chris.

Cheers
Andi

Andi, I have prepared a few of the Loti for some of our shops racers, and in all cases the car did benefit from having the motor glued in along the full length and ends of the motor (I used shoe goo)....anything to reduce either longitudinal or torsional flex in this area on any car is critical......so if you chose to open the hole on the can end bulkhead and glue the motor in you will be fine....whether you open up the hole or not, you will still improve the cars by gluing the motor......there are now 4/5 thusly modified Loti now running around our tracks, all with happy owners.


On to your issues.....

1/ DO NOT grind a flat on the motor shaft!!........Locktite is a poor gap filler, is still somewhat soft when dry (especially when it is thick/asked to fill a gap) and like superglues works best on closely mating surfaces.
Additionally, although miniscule, the thought of the potential imbalance caused by grinding the motor shaft makes me feel ill.
Remove all oil etc. from the shaft with some alchohol etc. and you are good to go.

2/What tyres are you currently using, and what is your test track surface? The VRAA stipulates urethane/rubber tyres ( 7mm wide), and the urethane tyres from Paul Gage and Dart hobbies will provide all the grip you will need with these low powered cars. Most of the cars including the top 2/3 finishers in the last 2 years have been on these urethanes.
If you are having trouble sourcing them, please let me know.

3/ Do not worry about your car being sluggish.......they are all sluggish!!!.......you are used to a Policar 25K 050 motor with some torque, geared at roughly 3/1..........you have now experienced a gutless 15K motor geared at 2. something to 1...........Yes Sir, gutless is the word!!.......and I am sure that once sorted, your car will be competitive!!

Hope this helps, and let me know if you need any more bits.

Cheers
Chris Walker

[old23]

Thanks Chris for all the detailed suggestions. I've been building these cars for a while now, but I've learned that I'll never be too old to learn some new tricks from guys like you on this forum.

Stewart