Yanmar AF120 turf tyre retrofit

[CoyPatton]

OK so here's a project update, there have been some ups and downs but long story short, the new rims are on the machine and working great

I had the adapters machined, the finish was excellent, if anyone in the UK is interested I can forward the details of the shop as they were super helpful and competitively priced.

Here are some pics of the adapters:

Rear

View attachment 693584View attachment 693585View attachment 693588View attachment 693592

Front

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(sorry I have no pics of the front adapters before they were on the machine)

I had a number of problems along the way which I worked around. I originally intended to bolt the rear adapters from the back of the hub, meaning that the bolts would not need to be recessed on the front surface. Unfortunately I didn't have a thread gauge and I managed to get the bolt thread pitch wrong, so the threads on the hub were different than those on the adapter. As a result I decided to drill out the adapter and then drill a 28mm recess for the bolt and socket, which worked fine. Boy was I glad that I specified aluminium rather than mild steel!

On the front, I found it very hard to line up the two sets of threads (coming out of the hub and into the adapter). The bolts didn't go in 100% cleanly but they are holding firm.

I had the machine shop make the adapters with an inner recess that matches the centre of the hub, and with a new protrusion that matches the centre holes in the new rims. That way, the bolts are just holding the two surfaces together, but the load is primarily on the centre recess/protrusion. This wasn't the case with the design I was using as inspiration, I'm pretty sure the way I did it is stronger.

I made the front adapters as thin as possible - we went for 17mm in the end - in order to have the least impact on steering geometry. The rears are thicker as it makes no difference and will aid stability having a slightly wider track.

These are the rims on the machine:

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In practise I have found that there are no strange noises from the transmission with the new wheels, or at least none that weren't there before As far as I can tell, steering is unaffected by the increased track at the front (approx 35mm in total). Damage to the ground is drastically less than before, in fact I only see impact at the front on a full-lock turn. There is no wheel fouling anywhere on the machine, including at full lock.

Overall despite the setbacks I am very happy with the mod. I may have to get new adapters made for the front if the threads are badly damaged, but I'll find that out when I take them off. For the time being they are fine and I'm no longer getting in trouble for ruining the lawn!

One caution for you is that you have dissimilar metals in place. Your spacers are aluminum while your bolts and wheels are steel. This is a recipe for corrosion (quickly if in s humid area). If you did not and for others doing this, use an anti-seize product on any contact from dissimilar metals. It should mot have an effect on maintaining torque although vibration will.

 

[pumasong]

One caution for you is that you have dissimilar metals in place.

Well said - I had meant to coat all surfaces in copper grease but didn't get around to it in my excitement to get the new wheels on. I will do so, thanks for the reminder.