A gottle of gears

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A gottle of gears

Post  highpressure on Sun 12 Feb 2012, 2:32 am

Following on from a chat with Lynn on her pictures thread I have been investigating the diff and have now found the following

Having been assembling the diff over the last couple of days have a slight concern over the amount of "backlash" but have been fiddling this morning and have discovered the following. Checked with Lynn about the gap between pinions and bevel and seems that there is quite a lot on my set up. I dont know how much backlash ther should be or what is considered normal but when all washers are in place it is well over 2mm!! Considering also that there will be wear in use and the pinions will naturally be thrown out I want to reduce this. My previous engine had a real chattering noise due to excessive backlash so want to start well.

The brass thrust washer measures 2.92mm and the steel packing washer is 1.98mm, if I remove the steel washer and replace it with 1mm temporary shims it gets the backlash to well below 1mm and reduces the chattering noise considerably. I dont think it will be possible to reduce the steel washer by 1mm but the brass one is a candidate. I dont know how to do this or if it is advisable so would like some input from Steve before going to town on the washer, but I dont see any harm in it and it can always be made bigger in the future.

I will call STW on Monday to see what Steve says but it not a major problem and seems easy to compensate for.

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Re: A gottle of gears

Post  lynnr on Sun 12 Feb 2012, 2:36 am

Hi

Yes. After further investigation. My diff is the same as yours. Lots of chatter from the Inner bevel gear.

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Re: A gottle of gears

Post  Rickster on Sun 12 Feb 2012, 3:43 am

Yes me too, I found exactly the same thing and was thinking of making the steel washer half its' thickness with the surface grinder at work.

I tried it without this packing washer and the teeth from the pinions and bevel actually seem to lock themselves to gether making the diff either imposible to move or too notchy.
I think Kevs' idea with the shims will allow correct thickness to be detemined but on early trials it seems about 1/2 the original thickness would do it.


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Re: A gottle of gears

Post  bjwlancashire on Sun 12 Feb 2012, 6:05 am

Intersting issue folks, I am curious to hear from Steve what the control model clearances/backlash is.

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Re: A gottle of gears

Post  highpressure on Sun 12 Feb 2012, 7:33 am

It all depends on what is considered to be an adequate backlash, personally I want a small gap as thats to be expected but not the current gap at well over 2mm. I want to hear what the "ideal setting" is.

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Re: A gottle of gears

Post  Steam Traction World on Sun 12 Feb 2012, 7:37 am

Hi Guys/Gals,

Both Steve and I knew that there would be every chance we may need to make an additional batch of shims for this kit. The control model is running perfect and smoothly but it did take us three or four attempts to get it right with a variety of different thickness shims. Once it was correct we then made every one elses shims identical to the control model ones. Short of putting together every single assembly this was the best we could achieve. The main issue to me was the inconsistancy with the batch of components we bought in. Like Steve said in an earlier post we did not have the time to send everything back so reworked it all ourselves.

Just spoken to Steve, we will order a selection of different thickness shims from the laser cutters tomorrow. Delivery is normally 5-7 days and as soon as we receive them we'll send them out.

I'm no expert but assembling the control model with Steve i noticed you need to make sure everything is as far back as it can go and that the main gear that the pinions revolve around is fitted right (and its really awkward as you can barely get to it!!). Even with Steve's years of knowledge and background it took us numerous attempts before everything ran smooth.

Dean

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Re: A gottle of gears

Post  lynnr on Sun 12 Feb 2012, 7:58 am

Cool. thought it was somethink like that.

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Re: A gottle of gears

Post  highpressure on Sun 12 Feb 2012, 1:44 pm

Excellent news Dean, that'll sort it out easily then, next time I ask if the stuff is ordered in pre done and the answer is "Yes that means there wont be too much work" we'll ignore that Very Happy

Now just to answer curiousity, I looked at the schedule for the kits because I was expecting to get both sides of the axle with this kit to lock on both wheels. So what else goes on the outside of the diff case? Clearly the threaded holes take something? Also what goes on the other end of the axle? Looking at the pictures of "The President" there just seems to be a sort of tubular lump. Is it just a spacer to interact with the wheel? and I suspect it comes with the kit with the gear guards and fly wheel then?

Cheers Kev.

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Re: A gottle of gears

Post  Steam Traction World on Sun 12 Feb 2012, 1:53 pm

Hi Kevin

The threaded holes in the Final Drive will be for a laser cut ring. This will keep the Winch where is supposed to be. We're actually machining the Winch Drums at the moment so this will form a major part of the next kit. The RH side of the engine will have a largeish casting that will be keyed to the axle and will take the drive from the axle into the RH wheel. Now we know that many axle lengths will be different, because of the diff shimming, we'll supply shims as standard with this kit.

Regards

Steve

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Re: A gottle of gears

Post  highpressure on Sun 12 Feb 2012, 2:17 pm

Thanks Steve, whilst you're here what is considered to be an acceptable amount of backlash? Just enough to allow the gears to move back and forth before engaging or a bit more or something altogether more precise like an actual measurement?

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Re: A gottle of gears

Post  Steam Traction World on Tue 14 Feb 2012, 12:34 am

Hi Kevin

The ideal is the smallest movement possible on all three pinions without the pinions bottoming out. In practice there is likely to be a difference between the three pinions so you will need to be governed by the tightest one. Donít spend a huge amount of time getting the set up to the nearest thou. It just ainít worth it. We ordered some different thickness shims from the laser cutters yesterday. These shims will get it to 0.5mm and thatís close enough

When I put our control model together I chose three different final drives and inner bevels. All three combinations worked well with the packing shims provided. Having said that three out of sixty is a pretty small sample but as you now know those final drive gears are quite heavy and Iím not as young as I used to be!

Regards

Steve

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Re: A gottle of gears

Post  lynnr on Tue 14 Feb 2012, 1:16 am

Thank you Steve.

I wait with bated breath for the padded envelope to arrive. Very Happy And I have paid my dues yesterday.

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Re: A gottle of gears

Post  Tony King on Wed 15 Feb 2012, 1:14 am

Hi All,
I just put my kit together & it looks like I'm one of the lucky ones, it all fits perfectly, runs as smooth as you like with next to no backlash!
Regards,
Tony

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